#### Sample records for perfusion diffusion confusion

ERIC Educational Resources Information Center

Hebrank, Mary R.

1997-01-01

Presents activities that allow students to explore the fundamental but poorly understood concept of diffusion by appealing to their kinesthetic senses first, then challenging their analytical skills as they try to deduce the mathematical principle involved. Presents a computer simulation of diffusion and discusses diffusion's limitations and…

ERIC Educational Resources Information Center

Hebrank, Mary R.

1997-01-01

Presents activities that allow students to explore the fundamental but poorly understood concept of diffusion by appealing to their kinesthetic senses first, then challenging their analytical skills as they try to deduce the mathematical principle involved. Presents a computer simulation of diffusion and discusses diffusion's limitations and…

3. Demonstrating Diffusion: Why the Confusion?

ERIC Educational Resources Information Center

Panizzon, Debra Lee

1998-01-01

Examines the principles of diffusion and how it may be confused with convection. Suggests that educators may be misleading students and clouding their understanding of the process. Provides two contemporary examples to explain the process of diffusion and how it differs from convection. (Author/CCM)

4. Demonstrating Diffusion: Why the Confusion?

ERIC Educational Resources Information Center

Panizzon, Debra Lee

1998-01-01

Examines the principles of diffusion and how it may be confused with convection. Suggests that educators may be misleading students and clouding their understanding of the process. Provides two contemporary examples to explain the process of diffusion and how it differs from convection. (Author/CCM)

5. Quorum sensing and the confusion about diffusion.

PubMed

West, Stuart A; Winzer, Klaus; Gardner, Andy; Diggle, Stephen P

2012-12-01

Two hypotheses, termed quorum sensing (QS) and diffusion sensing (DS), have been suggested as competing explanations for why bacterial cells use the local concentration of small molecules to regulate numerous extracellular behaviours. Here, we show that: (i) although there are important differences between QS and DS, they are not diametrically opposed; (ii) empirical attempts to distinguish between QS and DS are misguided and will lead to confusion; (iii) the fundamental distinction is not between QS and DS, but whether or not the trait being examined is social; (iv) empirical data are consistent with both social interactions and a role of diffusion; (v) alternate hypotheses, such as efficiency sensing (ES), are not required to unite QS and DS. More generally, work in this area illustrates how the use of jargon can obscure the underlying concepts and key questions. Copyright © 2012 Elsevier Ltd. All rights reserved.

6. [Perfusion computed tomography for diffuse liver diseases].

PubMed

Schmidt, S A; Juchems, M S

2012-08-01

Perfusion computed tomography (CT) has its main application in the clinical routine diagnosis of neuroradiological problems. Polyphase multi-detector spiral computed tomography is primarily used in liver diagnostics. The use of perfusion CT is also possible for the diagnostics and differentiation of diffuse hepatic diseases. The differentiation between cirrhosis and cirrhosis-like parenchymal changes is possible. It also helps to detect early stages of malignant tumors. However, there are some negative aspects, particularly that of radiation exposure. This paper summarizes the technical basics and possible applications of perfusion CT in cases of diffuse liver disease and weighs up the advantages and disadvantages of the examinations.

7. 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.

8. Quantitative measurement of tissue perfusion and diffusion in vivo.

PubMed

Chenevert, T L; Pipe, J G; Williams, D M; Brunberg, J A

1991-01-01

Magnetic resonance imaging techniques designed for sensitivity to microscopic motions of water diffusion and blood flow in the capillary network are also exceptionally sensitive to bulk motion properties of the tissue, which may lead to contrast artifact and large quantitative errors. The magnitude of bulk motion error that exists in human brain perfusion/diffusion imaging and the inability of cardiac gating to adequately control this motion are demonstrated by direct measurement of phase stability of voxels localized in the brain. Two methods are introduced to reduce bulk motion phase error. The first, a postprocessing phase correction algorithm, reduces coarse phase error but is inadequate by itself for quantitative perfusion/diffusion MRI. The second method employs orthogonal slice selection gradients to define a column of tissue in the object, from which echoes may be combined in a phase-insensitive manner to measure more reliably the targeted signal attenuation. Applying this acquisition technique and a simplistic model of perfusion and diffusion signal attenuations yields an estimated perfusion fraction of 3.4 +/- 1.1% and diffusion coefficient of 1.1 +/- 0.2 x 10(-5) cm2/s in the white matter of one normal volunteer. Successful separation of perfusion and diffusion effects by this technique is supported in a dynamic study of calf muscle. Periods of normal blood flow, low flow, and reactive hyperemia are clearly distinguished in the quantitative perfusion results, whereas measured diffusion remained nearly constant.

9. Diffusion, Perfusion, and Histopathologic Characteristics of Desmoplastic Infantile Ganglioglioma

PubMed Central

Ho, Chang Y; Gener, Melissa; Bonnin, Jose; Kralik, Stephen F

2016-01-01

We present a case series of a rare tumor, the desmoplastic infantile ganglioglioma (DIG) with MRI diffusion and perfusion imaging quantification as well as histopathologic characterization. Four cases with pathologically-proven DIG had diffusion weighted imaging (DWI) and two of the four had dynamic susceptibility contrast imaging. All four tumors demonstrate DWI findings compatible with low-grade pediatric tumors. For the two cases with perfusion imaging, a higher relative cerebral blood volume was associated with higher proliferation index on histopathology for one of the cases. Our results are discussed in conjunction with a literature review. PMID:27761184

10. Comparison of computed tomography perfusion and magnetic resonance imaging perfusion-diffusion mismatch in ischemic stroke.

PubMed

Campbell, Bruce C V; Christensen, Søren; Levi, Christopher R; Desmond, Patricia M; Donnan, Geoffrey A; Davis, Stephen M; Parsons, Mark W

2012-10-01

Perfusion imaging has the potential to select patients most likely to respond to thrombolysis. We tested the correspondence of computed tomography perfusion (CTP)-derived mismatch with contemporaneous perfusion-diffusion magnetic resonance imaging (MRI). Acute ischemic stroke patients 3 to 6 hours after onset had CTP and perfusion-diffusion MRI within 1 hour, before thrombolysis. Relative cerebral blood flow (relCBF) and time to peak of the deconvolved tissue residue function (Tmax) were calculated. The diffusion lesion (diffusion-weighted imaging) was registered to the CTP slabs and manually outlined to its maximal visual extent. Volumetric accuracy of CT-relCBF infarct core (compared with diffusion-weighted imaging) was tested. To reduce false-positive low CBF regions, relCBF core was restricted to voxels within a relative time-to-peak (relTTP) >4 seconds for lesion region of interest. The MR-Tmax >6 seconds perfusion lesion was automatically segmented and registered to CTP. Receiver-operating characteristic analysis determined the optimal CT-Tmax threshold to match MR-Tmax >6 seconds. Agreement of these CT parameters with MR perfusion-diffusion mismatch in coregistered slabs was assessed (mismatch ratio >1.2, absolute mismatch >10 mL, infarct core <70 mL). In analysis of 49 patients (mean onset to CT, 213 minutes; mean CT to MR, 31 minutes), constraining relCBF <31% within the automated relTTP perfusion lesion region of interest reduced the median magnitude of volumetric error (vs diffusion-weighted imaging) from 47.5 mL to 15.8 mL (P<0.001). The optimal CT-Tmax threshold to match MR-Tmax >6 seconds was 6.2 seconds (95% confidence interval, 5.6-7.3 seconds; sensitivity, 91%; specificity, 70%; area under the curve, 0.87). Using CT-Tmax >6 seconds "penumbra" and relTTP-constrained relCBF "core," CT-based and MRI-based mismatch status was concordant in 90% (kappa=0.80). Quantitative CTP mismatch classification using relCBF and Tmax is similar to perfusion-diffusion

11. Advanced Techniques in Musculoskeletal Oncology: Perfusion, Diffusion, and Spectroscopy.

PubMed

Teixeira, Pedro A Gondim; Beaumont, Marine; Gabriela, Hossu; Bailiang, Chen; Verhaeghe, Jean-luc; Sirveaux, François; Blum, Alain

2015-12-01

The imaging characterization of musculoskeletal tumors can be challenging, and a significant number of lesions remain indeterminate when conventional imaging protocols are used. In recent years, clinical availability of functional imaging methods has increased. Functional imaging has the potential to improve tumor detection, characterization, and follow-up. The most frequently used functional methods are perfusion imaging, diffusion-weighted imaging (DWI), and MR proton spectroscopy (MRS). Each of these techniques has specific protocol requirements and diagnostic pitfalls that need to be acknowledged to avoid misdiagnoses. Additionally, the application of functional methods in the MSK system has various technical issues that need to be addressed to ensure data quality and comparability. In this article, the application of contrast-enhanced perfusion imaging, DWI, and MRS for the evaluation of bone and soft tissue tumors is discussed, with emphasis on acquisition protocols, technical difficulties, and current clinical indications.

12. Perfusion Imaging with a Freely Diffusible Hyperpolarized Contrast Agent

PubMed Central

Grant, Aaron K.; Vinogradov, Elena; Wang, Xiaoen; Lenkinski, Robert E.; Alsop, David C.

2011-01-01

Contrast agents that can diffuse freely into or within tissue have numerous attractive features for perfusion imaging. Here we present preliminary data illustrating the suitability of hyperpolarized 13C labeled 2-methylpropan-2-ol (also known as dimethylethanol, tertiary butyl alcohol and tert-butanol) as a freely diffusible contrast agent for magnetic resonance perfusion imaging. Dynamic 13C images acquired in rat brain with a balanced steady-state free precession (bSSFP) sequence following administration of hyperpolarized 2-methylpropan-2-ol show that this agent can be imaged with 2–4s temporal resolution, 2mm slice thickness, and 700 micron in-plane resolution while retaining adequate signal-to-noise ratio. 13C relaxation measurements on 2-methylpropan-2-ol in blood at 9.4T yield T1=46±4s and T2=0.55±0.03s. In the rat brain at 4.7T, analysis of the temporal dynamics of the bSSFP image intensity in tissue and venous blood indicate that 2-methylpropan-2-ol has a T2 of roughly 2–4s and a T1 of 43±24s. In addition, the images indicate that 2-methylpropan-2-ol is freely diffusible in brain and hence has a long residence time in tissue; this in turn makes it possible to image the agent continuously for tens of seconds. These characteristics show that 2-methylpropan-2-ol is a promising agent for robust and quantitative perfusion imaging in the brain and body. PMID:21432901

13. Reversible changes in diffusion- and perfusion-based imaging in cerebral venous sinus thrombosis.

PubMed

Lin, Ning; Wong, Andrew K; Lipinski, Lindsay J; Mokin, Maxim; Siddiqui, Adnan H

2016-02-01

Diffusion- and perfusion-based imaging studies are regularly used in patients with ischemic stroke. Cerebral venous sinus thrombosis (CVST) is a rare cause of stroke and is primarily treated by systemic anticoagulation. Endovascular intervention can be considered in cases of failed medical therapy, yet the prognostic value of diffusion- and perfusion-based imaging for CVST has not been clearly established. We present a patient with CVST whose abnormal findings on MRI and CT perfusion images were largely reversed after endovascular treatment.

14. Diffusion and perfusion: the keys to fat grafting.

PubMed

Khouri, Roger K; Khouri, Raoul-Emil R; Lujan-Hernandez, Jorge R; Khouri, Khalil R; Lancerotto, Luca; Orgill, Dennis P

2014-09-01

Fat grafting is now widely used in plastic surgery. Long-term graft retention can be unpredictable. Fat grafts must obtain oxygen via diffusion until neovascularization occurs, so oxygen delivery may be the overarching variable in graft retention. We studied the peer-reviewed literature to determine which aspects of a fat graft and the microenvironment surrounding a fat graft affect oxygen delivery and created 3 models relating distinct variables to oxygen delivery and graft retention. Our models confirm that thin microribbons of fat maximize oxygen transport when injected into a large, compliant, well-vascularized recipient site. The "Microribbon Model" predicts that, in a typical human, fat injections larger than 0.16 cm in radius will have a region of central necrosis. Our "Fluid Accommodation Model" predicts that once grafted tissues approach a critical interstitial fluid pressure of 9 mm Hg, any additional fluid will drastically increase interstitial fluid pressure and reduce capillary perfusion and oxygen delivery. Our "External Volume Expansion Effect Model" predicts the effect of vascular changes induced by preoperative external volume expansion that allow for greater volumes of fat to be successfully grafted. These models confirm that initial fat grafting survival is limited by oxygen diffusion. Preoperative expansion increases oxygen diffusion capacity allowing for additional graft retention. These models provide a scientific framework for testing the current fat grafting theories.

15. Microfluidic perfusion for regulating diffusible signaling in stem cells.

PubMed

Blagovic, Katarina; Kim, Lily Y; Voldman, Joel

2011-01-01

\\paracrine processes previously hidden in conventional culture systems, our results establish microfluidic perfusion as a technique to study and manipulate diffusible signaling in cell systems.

16. Microfluidic Perfusion for Regulating Diffusible Signaling in Stem Cells

PubMed Central

Blagovic, Katarina; Kim, Lily Y.; Voldman, Joel

2011-01-01

-independent pathways. Overall, by uncovering autocrine\\paracrine processes previously hidden in conventional culture systems, our results establish microfluidic perfusion as a technique to study and manipulate diffusible signaling in cell systems. PMID:21829665

17. Vascular aspects of water uptake mechanisms in the toad skin: perfusion, diffusion, confusion.

PubMed

Willumsen, Niels J; Viborg, Arne L; Hillyard, Stanley D

2007-09-01

Blood cell flow (BCF) in the water absorbing "seat patch" region of toad skin was measured with laser Doppler flow cytometry. BCF of dehydrated toads increased by a factor of 6-8 when water contact was made and declined gradually as toads rehydrated. Water absorption was initially stimulated and declined in parallel with BCF. Water absorption measured during the initial rehydration period did not correlate with BCF and hydrated toads injected with AVT increased water absorption without an increase in BCF indicating the lack of an obligate relation between blood flow and water absorption. Aquaporins 1-3 were characterized by RT-PCR analysis of seat patch skin. AQP 1 was localized in the endothelium of subepidermal capillaries and serves as a pathway for water absorption in series with the apical and basolateral membranes of the epithelium. Dehydrated toads rehydrated more rapidly from dilute NaCl solutions than from deionized water despite the reduced osmotic gradient. BCF of toads rehydrating on 50 mM NaCl was not different than on deionized water and blocking Na+ transport with 100 microM amiloride did not reduce water absorption from 50 mM NaCl. Thus, neither circulation nor solute coupling explains the greater absorption from dilute salt solutions. Rehydration from 10 mM CaCl2 was stimulated above that of DI water by a similar degree as with 50 mM NaCl suggesting the anion might control water permeability of the skin.

18. Thrombolysis, Complete Recanalization, Diffusion Reversal, and Luxury Perfusion in Hyperacute Stroke.

PubMed

Sakamoto, Yuki; Ouchi, Takahiro; Okubo, Seiji; Abe, Arata; Aoki, Junya; Nogami, Akane; Sato, Takahiro; Hokama, Hiroyuki; Ogawa, Yutaro; Suzuki, Shizuka; Mishina, Masahiro; Kimura, Kazumi

2016-01-01

A 59-year old man was admitted to our stroke care unit 1.8 hours after onset of cardioembolic stroke. Administration of issue-plasminogen activator achieved complete recanalization, and his lesion on diffusion-weighted imaging (DWI) disappeared and single photon emission computed tomography showed luxury perfusion. DWI reversal and luxury perfusion were sometimes observed in hyperacute stroke patients, especially timely reperfusion was achieved. However, the relationships between DWI reversal and luxury perfusion were not well known. Transient DWI reversal may be associated with luxury perfusion in patients treated with t-PA, via early complete recanalization achieved by thrombolysis.

19. Design verification of a compact system for detecting tissue perfusion using bimodal diffuse optical technologies

Pakela, Julia M.; Hedrick, Taylor L.; Lee, Seung Yup; Vishwanath, Karthik; Zanfardino, Sara; Chung, Yooree G.; Helton, Michael C.; Kolodziejski, Noah J.; Stapels, Christopher J.; McAdams, Daniel R.; Fernandez, Daniel E.; Christian, James F.; Feinberg, Stephen E.; Mycek, Mary-Ann

2017-02-01

It is essential to monitor tissue perfusion during and after reconstructive surgery, as restricted blood flow can result in graft failures. Current clinical procedures are insufficient to monitor tissue perfusion, as they are intermittent and often subjective. To address this unmet clinical need, a compact, low-cost, multimodal diffuse correlation spectroscopy and diffuse reflectance spectroscopy system was developed. We verified system performance via tissue phantoms and experimental protocols for rigorous bench testing. Quantitative data analysis methods were employed and tested to enable the extraction of tissue perfusion parameters. This design verification study assures data integrity in future in vivo studies.

20. Real-time Diffusion-Perfusion Mismatch Analysis in Acute Stroke

PubMed Central

Straka, Matus; Albers, Gregory W.; Bammer, Roland

2010-01-01

Diffusion-perfusion mismatch can be used to identify acute stroke patients that could benefit from reperfusion therapies. Early assessment of the mismatch facilitates necessary diagnosis and treatment decisions in acute stroke. We developed the RApid processing of PerfusIon and Diffusion (RAPID) for unsupervised, fully automated processing of perfusion and diffusion data for the purpose of expedited routine clinical assessment. The RAPID system computes quantitative perfusion maps (CBV, CBF, MTT, and Tmax) using deconvolution of tissue and arterial signals. DWI/PWI mismatch is automatically determined using infarct core segmentation of ADC maps and perfusion deficits segmented from Tmax maps. The performance of the RAPID was evaluated on 63 acute stroke cases, in which diffusion and perfusion lesion volumes were outlined by both a human reader and the RAPID system. The correlation of outlined lesion volumes obtained from both methods was r2 = 0.99 for DWI and r2 = 0.96 for PWI. For mismatch identification, RAPID showed 100% sensitivity and 91% specificity. The mismatch information is made available on the hospital's PACS within 5-7 minutes. Results indicate that the automated system is sufficiently accurate and fast enough to be used for routine care as well as in clinical trials. PMID:21031505

1. Decreases in Molecular Diffusion, Perfusion Fraction and Perfusion-Related Diffusion in Fibrotic Livers: A Prospective Clinical Intravoxel Incoherent Motion MR Imaging Study

PubMed Central

Lu, Pu-Xuan; Huang, Hua; Yuan, Jing; Zhao, Feng; Chen, Zhi-Yi; Zhang, Qinwei; Ahuja, Anil T.; Zhou, Bo-Ping; Wáng, Yì-Xiáng J.

2014-01-01

Purpose This study was aimed to determine whether pure molecular-based diffusion coefficient (D) and perfusion-related diffusion parameters (perfusion fraction f, perfusion-related diffusion coefficient D*) differ in healthy livers and fibrotic livers through intra-voxel incoherent motion (IVIM) MR imaging. Material and Methods 17 healthy volunteers and 34 patients with histopathologically confirmed liver fibrosis patients (stage 1 = 14, stage 2 = 8, stage 3& 4 = 12, METAVIR grading) were included. Liver MR imaging was performed at 1.5-T. IVIM diffusion weighted imaging sequence was based on standard single-shot DW spin echo-planar imaging, with ten b values of 10, 20, 40, 60, 80, 100, 150, 200, 400, 800 sec/mm2 respectively. Pixel-wise realization and regions-of-interest based quantification of IVIM parameters were performed. Results D, f, and D* in healthy volunteer livers and patient livers were 1.096±0.155 vs 0.917±0.152 (10−3 mm2/s, p = 0.0015), 0.164±0.021 vs 0.123±0.029 (p<0.0001), and 13.085±2.943 vs 9.423±1.737 (10−3 mm2/s, p<0.0001) respectively, all significantly lower in fibrotic livers. As the fibrosis severity progressed, D, f, and D* values decreased, with a trend significant for f and D*. Conclusion Fibrotic liver is associated with lower pure molecular diffusion, lower perfusion volume fraction, and lower perfusion-related diffusion. The decrease of f and D* in the liver is significantly associated liver fibrosis severity. PMID:25436458

2. The New Triad. Diffusion, Illusion, and Confusion in the Nuclear Mission

DTIC Science & Technology

2016-09-01

lack of intellectual coherence and resulting confusion regarding the role of nuclear weapons in US national security strategy highlighted in the paper...second formal Nuclear Posture Review intended to develop top-level guidance regarding the role of nuclear weapons in national security strategy . While...defined hodgepodge termed “responsive infrastructure,” all bound together and supported by command and control (C2), intelligence, and planning

3. Visual assessment of perfusion-diffusion mismatch is inadequate to select patients for thrombolysis.

PubMed

Campbell, Bruce C V; Christensen, Søren; Foster, Sarah J; Desmond, Patricia M; Parsons, Mark W; Butcher, Kenneth S; Barber, P Alan; Levi, Christopher R; Bladin, Christopher F; Donnan, Geoffrey A; Davis, Stephen M

2010-01-01

For MR perfusion-diffusion mismatch to be clinically useful as a means of selecting patients for thrombolysis, it needs to occur in real time at the MRI console. Visual mismatch assessment has been used clinically and in trials but has not been systematically validated. We compared the accuracy of visually rating console-generated images with offline volumetric measurements using data from the Echoplanar Imaging Thrombolytic Evaluation Trial (EPITHET). Perfusion time-to-peak (TTP) and diffusion-weighted images (DWI) (as generated by commercial MRI console software) and T(max) perfusion maps (which required offline calculation) were visually rated. Perfusion-diffusion mismatch, defined as a ratio of perfusion:diffusion lesion volume of >1.2, was independently scored by 1 expert and 2 inexperienced raters blinded to calculated volumes and clinical information. Visual mismatch was compared with region-of-interest-based volumetric calculation, which was used as the gold standard. Volumetric calculation demonstrated perfusion-diffusion mismatch in 85/99 patients. Visual TTP-DWI mismatch was correctly classified by the experienced rater in 82% of the cases (sensitivity: 0.86; specificity: 0.54) compared to 73% for the inexperienced raters (sensitivity: 0.75; specificity: 0.57). The interrater reliability for TTP-DWI mismatch was moderate (kappa = 0.50). Visual T(max)-DWI mismatch performed better (agreement - 93 and 87%, sensitivity - 95 and 88%, specificity - 77 and 82% for the experienced and inexperienced raters, respectively). The assessment of visual TTP-DWI mismatch at the MRI console is insufficiently reliable for use in clinical trials. Differences in perfusion analysis technique and visual inaccuracies combine to make visual TTP-DWI mismatch substantially different to volumetric T(max)-DWI mismatch. Automated software that applies perfusion thresholds may improve the reproducibility of real-time mismatch assessment. Copyright 2010 S. Karger AG, Basel.

4. Brain/language relationships identified with diffusion and perfusion MRI: Clinical applications in neurology and neurosurgery.

PubMed

Hillis, Argye E

2005-12-01

Diffusion and perfusion MRI have contributed to stroke management by identifying patients with tissue "at risk" for further damage in acute stroke. However, the potential usefulness of these imaging modalities, along with diffusion tensor imaging, can be expanded by using these imaging techniques with concurrent assessment of language and other cognitive skills to identify the specific cognitive deficits that are associated with diffusion and perfusion abnormalities in particular brain regions. This paper illustrates how this combined behavioral and imaging methodology can yield information that is useful for predicting specific positive effects of intervention to restore blood flow in hypoperfused regions of brain identified with perfusion MRI, and for predicting negative effects of resection of particular brain regions or fiber bundles. Such data allow decisions about neurological and neurosurgical interventions to be based on specific risks and benefits in terms of functional consequences.

5. Interictal diffusion and perfusion magnetic resonance imaging features of cats with familial spontaneous epilepsy.

PubMed

Mizoguchi, Shunta; Hasegawa, Daisuke; Hamamoto, Yuji; Yu, Yoshihiko; Kuwabara, Takayuki; Fujiwara-Igarashi, Aki; Fujita, Michio

2017-03-01

OBJECTIVE To evaluate the usefulness of diffusion and perfusion MRI of the cerebrum in cats with familial spontaneous epilepsy (FSECs) and identify microstructural and functional deficit zones in affected cats. ANIMALS 19 FSECs and 12 healthy cats. PROCEDURES Diffusion-weighted, diffusion tensor, and perfusion-weighted MRI of the cerebrum were performed during interictal periods in FSECs. Imaging findings were compared between FSECs and control cats. Diffusion (apparent diffusion coefficient and fractional anisotropy) and perfusion (relative cerebral blood volume [rCBV], relative cerebral blood flow [rCBF], and mean transit time) variables were measured bilaterally in the hippocampus, amygdala, thalamus, parietal cortex gray matter, and subcortical white matter. Asymmetry of these variables in each region was also evaluated and compared between FSECs and control cats. RESULTS The apparent diffusion coefficient of the total amygdala of FSECs was significantly higher, compared with that of control cats. The fractional anisotropy of the right side and total hippocampus of FSECs was significantly lower, compared with that of control cats. The left and right sides and total hippocampal rCBV and rCBF were significantly lower in FSECs than in control cats. The rCBV and rCBF of the parietal cortex gray matter in FSECs were significantly lower than in control cats. CONCLUSIONS AND CLINICAL RELEVANCE In FSECs, diffusion and perfusion MRI detected microstructural changes and hypoperfusion (lowered function) in the cerebrum during interictal periods from that of healthy cats. These findings indicated that diffusion and perfusion MRI may be useful for noninvasive evaluation of epileptogenic foci in cats.

6. Associations between diffusion and perfusion parameters, N-acetyl aspartate, and lactate in acute ischemic stroke.

PubMed

Cvoro, Vera; Wardlaw, Joanna M; Marshall, Ian; Armitage, Paul A; Rivers, Carly S; Bastin, Mark E; Carpenter, Trevor K; Wartolowska, Karolina; Farrall, Andrew J; Dennis, Martin S

2009-03-01

In acute ischemic stroke, the amount of neuronal damage in hyperintense areas on MR diffusion imaging (DWI) is unclear. We used spectroscopic imaging to measure N-acetyl aspartate (NAA, a marker of normal neurons) and lactate (a marker of ischemia) to compare with diffusion and perfusion values in the diffusion lesion in acute ischemic stroke. We recruited patients with acute ischemic stroke prospectively and performed MR diffusion weighted (DWI), perfusion, and spectroscopic imaging. We coregistered the images, outlined the visible diffusion lesion, and extracted metabolite, perfusion, and apparent diffusion coefficient (ADC) values from the diffusion lesion. 42 patients were imaged, from 1.5 to 24 hours after stroke. In the DWI lesion, although NAA was reduced, there was no correlation between NAA and ADC or perfusion values. However, raised lactate correlated with reduced ADC (Spearman rho=0.32, P=0.04) and prolonged mean transit time (MTT, rho=0.31, P=0.04). Increasing DWI lesion size was associated with lower NAA and higher lactate (rho=-0.44, P=0.003; rho=0.49, P=0.001 respectively); NAA fell with increasing times to imaging (rho=-0.3, P=0.03), but lactate did not change. Although larger confirmatory studies are needed, the correlation of ADC and MTT with lactate but not NAA suggests that ADC and MTT are better markers of the presence of ischemia than of cumulative neuronal loss. Further studies should define more precisely the rate of neuronal loss and relationship to diffusion and perfusion parameters with respect to the depth and duration of ischemia.

7. Separating blood and water: Perfusion and free water elimination from diffusion MRI in the human brain.

PubMed

Rydhög, Anna S; Szczepankiewicz, Filip; Wirestam, Ronnie; Ahlgren, André; Westin, Carl-Fredrik; Knutsson, Linda; Pasternak, Ofer

2017-08-01

The assessment of the free water fraction in the brain provides important information about extracellular processes such as atrophy and neuroinflammation in various clinical conditions as well as in normal development and aging. Free water estimates from diffusion MRI are assumed to account for freely diffusing water molecules in the extracellular space, but may be biased by other pools of molecules in rapid random motion, such as the intravoxel incoherent motion (IVIM) of blood, where water molecules perfuse in the randomly oriented capillary network. The goal of this work was to separate the signal contribution of the perfusing blood from that of free-water and of other brain diffusivities. The influence of the vascular compartment on the estimation of the free water fraction and other diffusivities was investigated by simulating perfusion in diffusion MRI data. The perfusion effect in the simulations was significant, especially for the estimation of the free water fraction, and was maintained as long as low b-value data were included in the analysis. Two approaches to reduce the perfusion effect were explored in this study: (i) increasing the minimal b-value used in the fitting, and (ii) using a three-compartment model that explicitly accounts for water molecules in the capillary blood. Estimation of the model parameters while excluding low b-values reduced the perfusion effect but was highly sensitive to noise. The three-compartment model fit was more stable and additionally, provided an estimation of the volume fraction of the capillary blood compartment. The three-compartment model thus disentangles the effects of free water diffusion and perfusion, which is of major clinical importance since changes in these components in the brain may indicate different pathologies, i.e., those originating from the extracellular space, such as neuroinflammation and atrophy, and those related to the vascular space, such as vasodilation, vasoconstriction and capillary density

8. Mathematical Models of Diffusion-Limited Gas Bubble Evolution in Perfused Tissue

DTIC Science & Technology

Mathematical models of gas and bubble dynamics in tissue are used in various algorithms to mitigate the incidence and severity of decompression ... sickness (DCS) in man. These are simple models that describe the diffusion and perfusion processes that underlie gas bubble growth and resolution in terms

9. TOPICAL REVIEW: The measurement of diffusion and perfusion in biological systems using magnetic resonance imaging

Thomas, David L.; Lythgoe, Mark F.; Pell, Gaby S.; Calamante, Fernando; Ordidge, Roger J.

2000-08-01

The aim of this review is to describe two recent developments in the use of magnetic resonance imaging (MRI) in the study of biological systems: diffusion and perfusion MRI. Diffusion MRI measures the molecular mobility of water in tissue, while perfusion MRI measures the rate at which blood is delivered to tissue. Therefore, both these techniques measure quantities which have direct physiological relevance. It is shown that diffusion in biological systems is a complex phenomenon, influenced directly by tissue microstructure, and that its measurement can provide a large amount of information about the organization of this structure in normal and diseased tissue. Perfusion reflects the delivery of essential nutrients to tissue, and so is directly related to its status. The concepts behind the techniques are explained, and the theoretical models that are used to convert MRI data to quantitative physical parameters are outlined. Examples of current applications of diffusion and perfusion MRI are given. In particular, the use of the techniques to study the pathophysiology of cerebral ischaemia/stroke is described. It is hoped that the biophysical insights provided by this approach will help to define the mechanisms of cell damage and allow evaluation of therapies aimed at reducing this damage.

10. Perfusion and diffusion MRI of glioblastoma progression in a four-year prospective temozolomide clinical trial

SciTech Connect

Leimgruber, Antoine; Ostermann, Sandrine; Yeon, Eun Jo; Buff, Evelyn; Maeder, Philippe P.; Stupp, Roger; Meuli, Reto A. . E-mail: Reto.Meuli@chuv.ch

2006-03-01

Purpose: This study was performed to determine the impact of perfusion and diffusion magnetic resonance imaging (MRI) sequences on patients during treatment of newly diagnosed glioblastoma. Special emphasis has been given to these imaging technologies as tools to potentially anticipate disease progression, as progression-free survival is frequently used as a surrogate endpoint. Methods and Materials: Forty-one patients from a phase II temolozomide clinical trial were included. During follow-up, images were integrated 21 to 28 days after radiochemotherapy and every 2 months thereafter. Assessment of scans included measurement of size of lesion on T1 contrast-enhanced, T2, diffusion, and perfusion images, as well as mass effect. Classical criteria on tumor size variation and clinical parameters were used to set disease progression date. Results: A total of 311 MRI examinations were reviewed. At disease progression (32 patients), a multivariate Cox regression determined 2 significant survival parameters: T1 largest diameter (p < 0.02) and T2 size variation (p < 0.05), whereas perfusion and diffusion were not significant. Conclusion: Perfusion and diffusion techniques cannot be used to anticipate tumor progression. Decision making at disease progression is critical, and classical T1 and T2 imaging remain the gold standard. Specifically, a T1 contrast enhancement over 3 cm in largest diameter together with an increased T2 hypersignal is a marker of inferior prognosis.

11. The measurement of diffusion and perfusion in biological systems using magnetic resonance imaging.

PubMed

Thomas, D L; Lythgoe, M F; Pell, G S; Calamante, F; Ordidge, R J

2000-08-01

The aim of this review is to describe two recent developments in the use of magnetic resonance imaging (MRI) in the study of biological systems: diffusion and perfusion MRI. Diffusion MRI measures the molecular mobility of water in tissue, while perfusion MRI measures the rate at which blood is delivered to tissue. Therefore, both these techniques measure quantities which have direct physiological relevance. It is shown that diffusion in biological systems is a complex phenomenon, influenced directly by tissue microstructure, and that its measurement can provide a large amount of information about the organization of this structure in normal and diseased tissue. Perfusion reflects the delivery of essential nutrients to tissue, and so is directly related to its status. The concepts behind the techniques are explained, and the theoretical models that are used to convert MRI data to quantitative physical parameters are outlined. Examples of current applications of diffusion and perfusion MRI are given. In particular, the use of the techniques to study the pathophysiology of cerebral ischaemia/stroke is described. It is hoped that the biophysical insights provided by this approach will help to define the mechanisms of cell damage and allow evaluation of therapies aimed at reducing this damage.

12. Intracellular volume and apparent diffusion constants of perfused cancer cell cultures, as measured by NMR.

PubMed

Pilatus, U; Shim, H; Artemov, D; Davis, D; van Zijl, P C; Glickson, J D

1997-06-01

Diffusion NMR spectroscopy was used to study intracellular volume and apparent water diffusion constants in different cell lines (DU145, human prostate cancer; AT3, rat prostate cancer; MCF-7, human breast cancer; RIF-1, mouse fibrosacroma). The cells were grown on various matrices (collagen sponge, collagen beads, polystyrene beads) which enabled continuous growth in perfused high density cell culture suitable for NMR studies. In perfused cell systems, the attenuation of the water signal versus the squared gradient strength was fitted by the sum of two decaying exponentials. For the slowly decaying component the apparent water diffusion constant at 37 degrees C was 0.22 (+/-0.02) x 10(-9) s/m2 for all cell lines at diffusion times > 100 ms. It continuously increased up to 0.47 (+/-0.05) x 10(-9) s/m2 when the diffusion time was decreased to 8 ms, indicating restricted diffusion. No significant effect of the matrices was observed. The fractional volume of the slow component as determined from the biexponential diffusion curve correlated with the relative intracellular volume, as obtained from the cell density in the sample and the cell size as measured by light microscopy. Therefore, this simple NMR approach can be used to determine intracellular volume in perfused cell cultures suitable for NMR studies. Using this information in combination with spectroscopic data, changes in intracellular metabolite concentration can be detected even when the cellular volume is changing during the experiment. The apparent diffusion constant for the fast diffusing component varied with growth matrix, cell density and cell type and also showed the typical characteristics of restricted diffusion (increase of apparent diffusion constant with time).

13. Perfusion-diffusion mismatch: does it identify who will benefit from reperfusion therapy?

PubMed

Powers, William J

2012-06-01

A method to determine which patients would benefit from reperfusion therapies after 4.5 h would greatly add to our ability to reduce the disability caused by stroke. The goal of magnetic resonance perfusion-diffusion imaging in hyperacute ischemic stroke is to identify regions of the brain that will die if untreated and will live and regain function if quickly reperfused. The clinical value of perfusion-diffusion imaging in hyperacute ischemic stroke can be proven only by demonstrating empirically in a randomized controlled trial (RCT) that there is an improvement in patient outcome that depends on the use of the neuroimaging modality to guide therapy. To date, there have been only a few RCTs that have evaluated whether perfusion-diffusion imaging can identify a subgroup of patients with ischemic stroke more than 4.5 h from onset in whom the overall benefit from reperfusion therapy outweighs the risk. None have met the rigorous design requirements of the three-group study necessary to adequately test this hypothesis, and none have even met their own criteria for demonstrating a clinical benefit. While studies are not sufficient to conclusively disprove the hypothesis there are no RCT data to support it, and thus, the clinical value of MRI perfusion-diffusion imaging in this setting remains unproven. It is worthy of further investigation in rigorously designed RCTs. However, the risks of symptomatic intracerebral hemorrhage with reperfusion therapies in acute ischemic stroke are proven. Unless RCT data are forthcoming to demonstrate that MRI perfusion-diffusion mismatch improves clinical outcome, it should not be used to guide delayed reperfusion therapy.

14. Discrepancy between microsphere and diffusible tracer estimates of perfusion to ischemic myocardium

SciTech Connect

Yoshida, S.; Akizuki, S.; Gowski, D.; Downey, J.M.

1985-08-01

This study critically tests the ability of microspheres to accurately measure perfusion to ischemic myocardium. The left anterior descending coronary artery was cannulated and perfused with arterial blood. The perfusion line was clamped, and a sidearm between the clamp and the cannula was opened to the atmosphere, allowing blood to flow retrograde from the distal segment of the artery. Measurement of regional blood flow during retrograde flow diversion with 15-micron microspheres revealed essentially zero flow to the perfused segment (0.005 ml X min-1 X g-1). Measurements under the same conditions by either /sup 86/Rb uptake or /sup 133/Xe washout revealed that an appreciable perfusion of the tissue persisted during retrograde flow diversion (0.043 and 0.11 ml X min-1 X g-1, respectively, for the 2 methods). Thus, the authors have identified a condition during which microspheres indicate zero flow to the tissue but diffusible tracers can both be washed in and washed out at a brisk rate. They conclude that with simple occlusion there is a hidden component of perfusion to an ischemic zone that cannot be measured by microspheres, causing them to underestimate flow by about 25% in that condition.

15. Validation of diffuse correlation spectroscopy for muscle blood flow with concurrent arterial spin labeled perfusion MRI

Yu, Guoqiang; Floyd, Thomas F.; Durduran, Turgut; Zhou, Chao; Wang, Jiongjiong; Detre, John A.; Yodh, Arjun G.

2007-02-01

Calf blood flow was measured simultaneously in healthy human subjects (n = 7) during cuff inflation and deflation using near-infrared diffuse correlation spectroscopy (DCS) and arterial spin labeled perfusion MRI (ASL-MRI). The DCS and ASL-MRI data exhibited highly correlated absolute and relative dynamic flow responses in each individual (p < 0.001). Peak flow variations during hyperemia were also significantly correlated, though more for relative (p = 0.003) than absolute (p = 0.016) flow. Repeated measurement variation was less than 8% for both modalities. The results provide much needed quantitative blood flow validation of the diffuse optical correlation method in humans.

16. Intratumor Heterogeneity of Perfusion and Diffusion in Clear-Cell Renal Cell Carcinoma: Correlation With Tumor Cellularity.

PubMed

Yuan, Qing; Kapur, Payal; Zhang, Yue; Xi, Yin; Carvo, Ingrid; Signoretti, Sabina; Dimitrov, Ivan E; Cadeddu, Jeffrey A; Margulis, Vitaly; Brugarolas, James; Madhuranthakam, Ananth J; Pedrosa, Ivan

2016-12-01

Magnetic resonance imaging (MRI) has the potential to noninvasively provide information about the tumor microenvironment. A correlation between arterial spin-labeled (ASL) MRI and tumor vasculature has been previously demonstrated; however, its correlation with tumor cellularity is unknown. We sought to assess intratumor heterogeneity of perfusion and diffusion in vivo in clear-cell renal cell carcinoma (ccRCC) using MRI and to correlate these findings with tumor vascularity and cellularity at histopathology. Twenty-three ccRCC patients underwent ASL and diffusion-weighted MRI before surgery after signing an informed consent in this prospective institutional review board-approved, HIPAA (Insurance Portability and Accountability Act)-compliant study. Quantitative ASL perfusion and diffusion were measured in 2 areas within the same tumor with high and low perfusion. Microvessel density (MVD) on CD31 and CD34 immunostains and tumor cellularity in anatomically coregistered tissue samples were correlated to MRI measurements (Spearman; P < .05 statistically significant). ASL perfusion (P < .0001), CD31 MVD (P = .02), CD34 MVD (P = .04), and cellularity (P = .002) from high and low perfusion areas were significantly different across all tumors. There were positive correlations between tumor cellularity and CD31 MVD (ρ = 0.350, P = .021), CD31 and CD34 MVD (ρ = 0.838, P < .0001), ASL perfusion and cellularity (ρ = 0.406, P = .011), and ASL perfusion and CD31 MVD (ρ = 0.468, P = .003), and a negative correlation between tissue diffusion coefficient and cellularity (ρ = -0.316, P = .039). Tumor areas with high ASL perfusion exhibit higher cellularity and MVD compared to areas with low perfusion in the same tumor. A positive correlation between tumor vascularity and cellularity in ccRCC is newly reported. A negative correlation between tumor diffusion and cellularity is confirmed. Copyright © 2016 Elsevier Inc. All rights reserved.

17. Comparison of stroke infarction between CT perfusion and diffusion weighted imaging: preliminary results

Abd. Rahni, Ashrani Aizzuddin; Arka, Israna Hossain; Chellappan, Kalaivani; Mukari, Shahizon Azura; Law, Zhe Kang; Sahathevan, Ramesh

2016-03-01

In this paper we present preliminary results of comparison of automatic segmentations of the infarct core, between that obtained from CT perfusion (based on time to peak parameter) and diffusion weighted imaging (DWI). For each patient, the two imaging volumes were automatically co-registered to a common frame of reference based on an acquired CT angiography image. The accuracy of image registration is measured by the overlap of the segmented brain from both images (CT perfusion and DWI), measured within their common field of view. Due to the limitations of the study, DWI was acquired as a follow up scan up to a week after initial CT based imaging. However, we found significant overlap of the segmented brain (Jaccard indices of approximately 0.8) and the percentage of infarcted brain tissue from the two modalities were still fairly highly correlated (correlation coefficient of approximately 0.9). The results are promising with more data needed in future for clinical inference.

18. Pharmacodynamic effect of dipyridamole on thallium-201 myocardial perfusion in progressive systemic sclerosis with diffuse scleroderma.

PubMed Central

Kahan, A; Devaux, J Y; Amor, B; Menkes, C J; Weber, S; Foult, J M; Venot, A; Guerin, F; Degeorges, M; Roucayrol, J C

1986-01-01

We evaluated the effect of dipyridamole on thallium-201 myocardial perfusion in 23 patients with progressive systemic sclerosis (PSS) with diffuse scleroderma. Thallium-201 single photon emission computed tomography (SPECT) was performed at rest and after coronary artery vasodilatation with intravenous dipyridamole (0.14 mg/kg/min for four minutes). The left myocardium was divided into nine segments; each segment was graded as 2.0, 1.5, 1.0, 0.5, 0 (zero represents no activity). Dipyridamole significantly improved resting thallium-201 myocardial perfusion: the mean (SD) number of segments with thallium defects decreased from 6.0 (2.1) at rest to 4.1 (2.5) after dipyridamole (p less than 0.0001); the mean (SD) score in segments with resting defects increased from 0.92 (0.24) at rest to 1.13 (0.38) after dipyridamole (p less than 0.0001); the mean (SD) global score per patient increased from 10.2 (1.8) at rest to 11.4 (2.1) after dipyridamole (p less than 0.02); the global score increased by at least 2.0 in 12 patients and worsened by at least 2.0 in three patients only (p = 0.05). The results of this acute study suggest that some drugs with potent vasodilator activity on small coronary arteries may be beneficial in the treatment of PSS patients with thallium-201 myocardial perfusion abnormalities. Images PMID:3490227

19. Perfusion-diffusion compartmental models describe cerebral helium kinetics at high and low cerebral blood flows in sheep.

PubMed

Doolette, David J; Upton, Richard N; Grant, Cliff

2005-03-01

This study evaluated the relative importance of perfusion and diffusion mechanisms in compartmental models of blood:tissue helium exchange in the brain. Helium has different physiochemical properties from previously studied gases, and is a common diluent gas in underwater diving where decompression schedules are based on theoretical models of inert gas kinetics. Helium kinetics across the cerebrum were determined during and after 15 min of helium inhalation, at separate low and high steady states of cerebral blood flow in seven sheep under isoflurane anaesthesia. Helium concentrations in arterial and sagittal sinus venous blood were determined using gas chromatographic analysis, and sagittal sinus blood flow was monitored continuously. Parameters and model selection criteria of various perfusion-limited or perfusion-diffusion compartmental models of the brain were estimated by simultaneous fitting of the models to the sagittal sinus helium concentrations for both blood flow states. Purely perfusion-limited models fitted the data poorly. Models that allowed a diffusion-limited exchange of helium between a perfusion-limited tissue compartment and an unperfused deep compartment provided better overall fit of the data and credible parameter estimates. Fit to the data was also improved by allowing countercurrent diffusion shunt of helium between arterial and venous blood. These results suggest a role of diffusion in blood:tissue helium equilibration in brain.

20. Methylene blue treatment delays progression of perfusion-diffusion mismatch to infarct in permanent ischemic stroke.

PubMed

Rodriguez, Pavel; Jiang, Zhao; Huang, Shiliang; Shen, Qiang; Duong, Timothy Q

2014-11-07

Stroke is a leading cause of morbidity and mortality in the world. Low-dose methylene blue (MB), which has been used safely to treat methemoglobinemia and cyanide poisoning in humans, has energy enhancing and antioxidant properties. We tested the hypothesis that methylene blue treatment delays progression of at-risk tissue (ca. perfusion-diffusion mismatch) to infarct in permanent middle cerebral artery occlusion in rats at two MB treatment doses. Serial MRI was used to evaluate MB treatment efficacy. The major findings were: (i) MB significantly prolonged the perfusion-diffusion mismatch, (ii) MB mildly increased the CBF in the hypoperfused tissue, (iii) MB did not change the final infarct volume in permanent ischemic stroke, and (iv) there were no dose-dependent effects on mismatch progression for the 1 and 3mg/kg doses studied. This neuroprotective effect is likely the result of sustained ATP production and increased CBF to tissue at risk. This work has the potential to readily lead to clinical stroke trials given MB's excellent safety profile.

1. Reversal of diffuse patchy pattern in lung perfusion scan in a case of severe pulmonary arterial hypertension.

PubMed

Kodama, Yoshihiko; Abe, Kohtaro; Hosokawa, Kazuya; Ohtani, Kisho; Nagao, Michinobu; Hirooka, Yoshitaka; Sunagawa, Kenji

2015-01-01

A diffuse patchy pattern in the perfusion scan of the lung is a hallmark of severe pulmonary arterial hypertension (PAH). However, the mechanisms of this unique pattern remain uncertain. We here present the case of a 19-year-old woman with severe PAH who demonstrated reversal of the diffuse patchy pattern with improvement of pulmonary blood flow within a month after upfront triple combination therapy. Our case is a first report showing reversibility of diffuse patchy pattern by a short-term treatment in severe PAH. These findings suggest the possibility that the mechanisms underlying the diffuse patchy pattern may involve reversible vasoconstriction in addition to remodeling of small pulmonary arteries.

2. Comparison of perfusion- and diffusion-weighted imaging parameters in brain tumor studies processed using different software platforms.

PubMed

Milchenko, Mikhail V; Rajderkar, Dhanashree; LaMontagne, Pamela; Massoumzadeh, Parinaz; Bogdasarian, Ronald; Schweitzer, Gordon; Benzinger, Tammie; Marcus, Dan; Shimony, Joshua S; Fouke, Sarah Jost

2014-10-01

To compare quantitative imaging parameter measures from diffusion- and perfusion-weighted imaging magnetic resonance imaging (MRI) sequences in subjects with brain tumors that have been processed with different software platforms. Scans from 20 subjects with primary brain tumors were selected from the Comprehensive Neuro-oncology Data Repository at Washington University School of Medicine (WUSM) and the Swedish Neuroscience Institute. MR images were coregistered, and each subject's data set was processed by three software packages: 1) vendor-specific scanner software, 2) research software developed at WUSM, and 3) a commercially available, Food and Drug Administration-approved, processing platform (Nordic Ice). Regions of interest (ROIs) were chosen within the brain tumor and normal nontumor tissue. The results obtained using these methods were compared. For diffusion parameters, including mean diffusivity and fractional anisotropy, concordance was high when comparing different processing methods. For perfusion-imaging parameters, a significant variance in cerebral blood volume, cerebral blood flow, and mean transit time (MTT) values was seen when comparing the same raw data processed using different software platforms. Correlation was better with larger ROIs (radii ≥ 5 mm). Greatest variance was observed in MTT. Diffusion parameter values were consistent across different software processing platforms. Perfusion parameter values were more variable and were influenced by the software used. Variation in the MTT was especially large suggesting that MTT estimation may be unreliable in tumor tissues using current MRI perfusion methods. Copyright © 2014 AUR. Published by Elsevier Inc. All rights reserved.

3. In vivo preclinical verification of a multimodal diffuse reflectance and correlation spectroscopy system for sensing tissue perfusion

Pakela, Julia M.; Lee, Seung Yup; Hedrick, Taylor L.; Vishwanath, Karthik; Helton, Michael C.; Chung, Yooree G.; Kolodziejski, Noah J.; Staples, Christopher J.; McAdams, Daniel R.; Fernandez, Daniel E.; Christian, James F.; O'Reilly, Jameson; Farkas, Dana; Ward, Brent B.; Feinberg, Stephen E.; Mycek, Mary-Ann

2017-02-01

In reconstructive surgery, impeded blood flow in microvascular free flaps due to a compromise in arterial or venous patency secondary to blood clots or vessel spasms can rapidly result in flap failures. Thus, the ability to detect changes in microvascular free flaps is critical. In this paper, we report progress on in vivo pre-clinical testing of a compact, multimodal, fiber-based diffuse correlation and reflectance spectroscopy system designed to quantitatively monitor tissue perfusion in a porcine model's surgically-grafted free flap. We also describe the device's sensitivity to incremental blood flow changes and discuss the prospects for continuous perfusion monitoring in future clinical translational studies.

4. Alveolar ventilation to perfusion heterogeneity and diffusion impairment in a mathematical model of gas exchange

NASA Technical Reports Server (NTRS)

Vidal Melo, M. F.; Loeppky, J. A.; Caprihan, A.; Luft, U. C.

1993-01-01

This study describes a two-compartment model of pulmonary gas exchange in which alveolar ventilation to perfusion (VA/Q) heterogeneity and impairment of pulmonary diffusing capacity (D) are simultaneously taken into account. The mathematical model uses as input data measurements usually obtained in the lung function laboratory. It consists of two compartments and an anatomical shunt. Each compartment receives fractions of alveolar ventilation and blood flow. Mass balance equations and integration of Fick's law of diffusion are used to compute alveolar and blood O2 and CO2 values compatible with input O2 uptake and CO2 elimination. Two applications are presented. The first is a method to partition O2 and CO2 alveolar-arterial gradients into VA/Q and D components. The technique is evaluated in data of patients with chronic obstructive pulmonary disease (COPD). The second is a theoretical analysis of the effects of blood flow variation in alveolar and blood O2 partial pressures. The results show the importance of simultaneous consideration of D to estimate VA/Q heterogeneity in patients with diffusion impairment. This factor plays an increasing role in gas alveolar-arterial gradients as severity of COPD increases. Association of VA/Q heterogeneity and D may produce an increase of O2 arterial pressure with decreasing QT which would not be observed if only D were considered. We conclude that the presented computer model is a useful tool for description and interpretation of data from COPD patients and for performing theoretical analysis of variables involved in the gas exchange process.

5. Alveolar ventilation to perfusion heterogeneity and diffusion impairment in a mathematical model of gas exchange

NASA Technical Reports Server (NTRS)

Vidal Melo, M. F.; Loeppky, J. A.; Caprihan, A.; Luft, U. C.

1993-01-01

This study describes a two-compartment model of pulmonary gas exchange in which alveolar ventilation to perfusion (VA/Q) heterogeneity and impairment of pulmonary diffusing capacity (D) are simultaneously taken into account. The mathematical model uses as input data measurements usually obtained in the lung function laboratory. It consists of two compartments and an anatomical shunt. Each compartment receives fractions of alveolar ventilation and blood flow. Mass balance equations and integration of Fick's law of diffusion are used to compute alveolar and blood O2 and CO2 values compatible with input O2 uptake and CO2 elimination. Two applications are presented. The first is a method to partition O2 and CO2 alveolar-arterial gradients into VA/Q and D components. The technique is evaluated in data of patients with chronic obstructive pulmonary disease (COPD). The second is a theoretical analysis of the effects of blood flow variation in alveolar and blood O2 partial pressures. The results show the importance of simultaneous consideration of D to estimate VA/Q heterogeneity in patients with diffusion impairment. This factor plays an increasing role in gas alveolar-arterial gradients as severity of COPD increases. Association of VA/Q heterogeneity and D may produce an increase of O2 arterial pressure with decreasing QT which would not be observed if only D were considered. We conclude that the presented computer model is a useful tool for description and interpretation of data from COPD patients and for performing theoretical analysis of variables involved in the gas exchange process.

6. Analytical estimation of ultrasound properties, thermal diffusivity, and perfusion using magnetic resonance-guided focused ultrasound temperature data

PubMed Central

Dillon, C R; Borasi, G; Payne, A

2016-01-01

For thermal modeling to play a significant role in treatment planning, monitoring, and control of magnetic resonance-guided focused ultrasound (MRgFUS) thermal therapies, accurate knowledge of ultrasound and thermal properties is essential. This study develops a new analytical solution for the temperature change observed in MRgFUS which can be used with experimental MR temperature data to provide estimates of the ultrasound initial heating rate, Gaussian beam variance, tissue thermal diffusivity, and Pennes perfusion parameter. Simulations demonstrate that this technique provides accurate and robust property estimates that are independent of the beam size, thermal diffusivity, and perfusion levels in the presence of realistic MR noise. The technique is also demonstrated in vivo using MRgFUS heating data in rabbit back muscle. Errors in property estimates are kept less than 5% by applying a third order Taylor series approximation of the perfusion term and ensuring the ratio of the fitting time (the duration of experimental data utilized for optimization) to the perfusion time constant remains less than one. PMID:26741344

7. Analytical estimation of ultrasound properties, thermal diffusivity, and perfusion using magnetic resonance-guided focused ultrasound temperature data

Dillon, C. R.; Borasi, G.; Payne, A.

2016-01-01

For thermal modeling to play a significant role in treatment planning, monitoring, and control of magnetic resonance-guided focused ultrasound (MRgFUS) thermal therapies, accurate knowledge of ultrasound and thermal properties is essential. This study develops a new analytical solution for the temperature change observed in MRgFUS which can be used with experimental MR temperature data to provide estimates of the ultrasound initial heating rate, Gaussian beam variance, tissue thermal diffusivity, and Pennes perfusion parameter. Simulations demonstrate that this technique provides accurate and robust property estimates that are independent of the beam size, thermal diffusivity, and perfusion levels in the presence of realistic MR noise. The technique is also demonstrated in vivo using MRgFUS heating data in rabbit back muscle. Errors in property estimates are kept less than 5% by applying a third order Taylor series approximation of the perfusion term and ensuring the ratio of the fitting time (the duration of experimental data utilized for optimization) to the perfusion time constant remains less than one.

8. Perfusion and diffusion imaging in acute focal cerebral ischemia: Temporal vs. spatial resolution

PubMed Central

Bardutzky, Juergen; Shen, Qiang; Bouley, James; Sotak, Christopher H.; Duong, Timothy Q.; Fisher, Marc

2010-01-01

High-resolution diffusion- (DWI) and perfusion-weighted (PWI) imaging may provide substantial benefits in accurate delineation of normal, ischemic, and at-risk tissue. We compared the capability of low (400 × 400 µm2) and high (200 × 200 µm2) spatial resolution imaging in characterizing the spatiotemporal evolution of the ischemic lesion in a permanent middle artery occlusion (MCAO) model in rats. Serial measurements of cerebral blood flow (CBF) and the apparent diffusion coefficient (ADC) were performed. Lesion volumes were calculated by using viability thresholds or by visual inspection, and correlated with infarct volume defined by TTC staining at 24 h after MCAO. At the very early phase of ischemia, high-resolution resulted in a significantly larger ADC-derived lesion volume and a smaller PWI/DWI mismatch. At 3 h after MCAO, ADC and CBF lesions showed similar robust correlations with TTC-defined infarct volumes for both groups using previously established thresholds. When lesions were determined visually, low-resolution resulted in a substantial overestimation of TTC-defined infarct volume and a lower inter-observer reliability (r = 0.75), whereas high-resolution produced an excellent correlation with TTC-defined infarct volume and inter-observer reliability (r = 0.96). In conclusion, high-resolution MRI resulted in substantial temporal averaging of the ischemic lesion during the early phase, but was clearly superior in visual determination of final infarct size. Low-resolution reasonably evaluated the temporal and spatial evolution of ischemia when thresholds were used. PMID:15862529

9. Perfusion and Diffusion Sensitive 13C Stimulated-echo MRSI for Metabolic Imaging of Cancer

PubMed Central

Larson, Peder E. Z.; Hurd, Ralph E.; Kerr, Adam B.; Pauly, John M.; Bok, Robert A.; Kurhanewicz, John; Vigneron, Daniel B.

2012-01-01

Metabolic imaging with hyperpolarized [1-13C]-pyruvate can rapidly probe tissue metabolic profiles in vivo and has been shown to provide cancer imaging biomarkers for tumor detection, progression, and response to therapy. This technique uses a bolus injection followed by imaging within 1–2 minutes. The observed metabolites includes vascular components and their generation is also influenced by cellular transport. These factors complicate image interpretation, especially since [1-13C]lactate, a metabolic product that is a biomarker of cancer, is also produced by red blood cells. It would be valuable to understand the distribution of metabolites between the vasculature, interstitial space, and intracellular compartments. The purpose of this study was to better understand this compartmentalization by using a perfusion and diffusion-sensitive stimulated-echo acquisition mode (STEAM) MRSI acquisition method tailored to hyperpolarized substrates. Our results in mouse models showed that among metabolites, the injected substrate 13C-pyruvate had the largest vascular fraction overall while 13C-alanine had the smallest vascular fraction. We observed a larger vascular fraction of pyruvate and lactate in the kidneys and liver when compared to back muscle and prostate tumor tissue. Our data suggests that 13C-lactate in prostate tumor tissue voxels was the most abundant labeled metabolite intracellularly. This was shown in STEAM images that highlighted abnormal cancer cell metabolism and suppressed vascular 13C metabolite signals. PMID:23260391

10. Complete Separation of Intracellular and Extracellular Information in NMR Spectra of Perfused Cells by Diffusion-Weighted Spectroscopy

van Zijl, Peter C. M.; Moonen, Chrit T. W.; Faustino, Patrick; Pekar, James; Kaplan, Ofer; Cohen, Jack S.

1991-04-01

A method is outlined that completely separates intracellular and extracellular information in NMR spectra of perfused cells. The technique uses diffusion weighting to exploit differences in motional properties between intra- and extracellular constituents. This allows monitoring of intracellular metabolism, and of transport of small drugs and nutrients through the cell membrane, under controlled physiological conditions. As a first example, proton spectra of drug-resistant MCF-7 human breast cancer cells are studied, and uptake of phenylalanine is monitored.

11. Development and validation of the random walk algorithm: application to the classification of diffuse heterogeneity in brain SPECT perfusion images.

PubMed

Modzelewski, Romain; de la Rue, Thierry; Janvresse, Elise; Hitzel, Anne; Menard, Jean François; Manrique, Alain; Gardin, Isabelle; Gerardin, Emmanuel; Hannequin, Didier; Vera, Pierre

2008-01-01

Heterogeneity analysis has been studied for radiological imaging, but few methods have been developed for functional images. Diffuse heterogeneous perfusion frequently appears in brain single photon emission computed tomography (SPECT) images, but objective quantification is lacking. An automatic method, based on random walk (RW) theory, has been developed to quantify perfusion heterogeneity. We assess the robustness of our algorithm in differentiating levels of diffuse heterogeneity even when focal defects are present. Heterogeneity is quantified by counting R (percentage), the mean rate of visited pixels in a fixed number of steps of the stochastic RW process. The algorithm has been tested on the numerical anthropomorphic Zubal head phantom. Seven diffuse cortical heterogeneity levels were simulated with an adjustable Gaussian function and 6 temporoparietal focal defects simulating Alzheimer Disease, leading to 42 phantoms. Data were projected and smoothed (full width at half maximum, 5.5 mm), and Poisson noise was added to the 64 projections. The SPECT data were reconstructed using filtered backprojection (Hamming filter, 0.5 c/p). R values for different levels of perfusion defect and diffuse heterogeneity were evaluated on 3 parameters: the number of slices studied (20 vs 40), the use of Talairach normalization versus original space, and the use of a cortical mask within the Talairach space. For each parameter, regression lines for heterogeneity and temporoparietal defect quantification were analyzed by covariance statistics. R values were also evaluated on SPECT images performed on 25 subjects with suspected focal dementia and on 15 normal controls. Scans were blindly ranked by 2 experienced nuclear physicians according to the degree of diffuse heterogeneity. Variability of R was smaller than 0.17% for repeated measurements. R was more particularly influenced by diffuse heterogeneity compared with focal perfusion defect. The Talairach normalization had a

12. Diffusion-weighted magnetic resonance imaging reveals the effects of different cooling temperatures on the diffusion of water molecules and perfusion within human skeletal muscle.

PubMed

Yanagisawa, O; Fukubayashi, T

2010-11-01

13. Diffusion model for iontophoresis measured by laser-Doppler perfusion flowmetry, applied to normal and preeclamptic pregnancies.

PubMed

de Mul, Frits F M; Blaauw, Judith; Aarnoudse, Jan G; Smit, Andries J; Rakhorst, Gerhard

2007-01-01

We present a physical model to describe iontophoresis time recordings. The model is a combination of monodimensional material diffusion and decay, probably due to transport by blood flow. It has four adjustable parameters, the diffusion coefficient, the decay constant, the height of the response, and the shot saturation constant, a parameter representing the relative importance of subsequent shots (in case of saturation). We test the model with measurements of blood perfusion in the capillary bed of the fingers of women who recently had preeclampsia and in women with a history of normal pregnancy. From the fits to the measurements, we conclude that the model provides a useful physical description of the iontophoresis process.

14. Production of Xylella fastidiosa diffusible signal factor in transgenic grape causes pathogen confusion and reduction in severity of Pierce's disease.

PubMed

Lindow, Steven; Newman, Karyn; Chatterjee, Subhadeep; Baccari, Clelia; Lavarone, Anthony T; Ionescu, Michael

2014-03-01

The rpfF gene from Xylella fastidiosa, encoding the synthase for diffusible signal factor (DSF), was expressed in 'Freedom' grape to reduce the pathogen's growth and mobility within the plant. Symptoms in such plants were restricted to near the point of inoculation and incidence of disease was two- to fivefold lower than in the parental line. Both the longitudinal and lateral movement of X. fastidiosa in the xylem was also much lower. DSF was detected in both leaves and xylem sap of RpfF-expressing plants using biological sensors, and both 2-Z-tetradecenoic acid, previously identified as a component of X. fastidiosa DSF, and cis-11-methyl-2-dodecenoic acid were detected in xylem sap using electrospray ionization mass spectrometry. A higher proportion of X. fastidiosa cells adhered to xylem vessels of the RpfF-expressing line than parental 'Freedom' plants, reflecting a higher adhesiveness of the pathogen in the presence of DSF. Disease incidence in RpfF-expressing plants in field trials in which plants were either mechanically inoculated with X. fastidiosa or subjected to natural inoculation by sharpshooter vectors was two- to fourfold lower in than that of the parental line. The number of symptomatic leaves on infected shoots was reduced proportionally more than the incidence of infection, reflecting a decreased ability of X. fastidiosa to move within DSF-producing plants.

15. A practical assessment of magnetic resonance diffusion-perfusion mismatch in acute stroke: observer variation and outcome.

PubMed

Kane, I; Hand, P J; Rivers, C; Armitage, P; Bastin, M E; Lindley, R; Dennis, M; Wardlaw, J M

2009-11-01

MR diffusion/perfusion mismatch may help identify patients for acute stroke treatment, but mixed results from clinical trials suggest that further evaluation of the mismatch concept is required. To work effectively, mismatch should predict prognosis on arrival at hospital. We assessed mismatch duration and associations with functional outcome in acute stroke. We recruited consecutive patients with acute stroke, recorded baseline clinical variables, performed MR diffusion and perfusion imaging and assessed 3-month functional outcome. We assessed practicalities, agreement between mismatch on mean transit time (MTT) or cerebral blood flow (CBF) maps, visually and with lesion volume, and the relationship of each to functional outcome. Of 82 patients starting imaging, 14 (17%) failed perfusion imaging. Overall, 42% had mismatch (56% at <6 h; 41% at 12-24 h; 23% at 24-48 h). Agreement for mismatch by visual versus volume assessment was fair using MTT (kappa 0.59, 95% CI 0.34-0.84) but poor using CBF (kappa 0.24, 95% CI 0.01-0.48). Mismatch by either definition was not associated with functional outcome, even when the analysis was restricted to just those with mismatch. Visual estimation is a reasonable proxy for mismatch volume on MTT but not CBF. Perfusion is more difficult for acute stroke patients than diffusion imaging. Mismatch is present in many patients beyond 12 h after stroke. Mismatch alone does not distinguish patients with good and poor prognosis; both can do well or poorly. Other factors, e.g. reperfusion, may influence outcome more strongly, even in patients without mismatch.

16. WE-G-18C-09: Separating Perfusion and Diffusion Components From Diffusion Weighted MRI of Rectum Tumors Based On Intravoxel Incoherent Motion (IVIM) Analysis

SciTech Connect

Tyagi, N; Wengler, K; Mazaheri, Y; Hunt, M; Deasy, J; Gollub, M

2014-06-15

Purpose: Pseudodiffusion arises from the microcirculation of blood in the randomly oriented capillary network and contributes to the signal decay acquired using a multi-b value diffusion weighted (DW)-MRI sequence. This effect is more significant at low b-values and should be properly accounted for in apparent diffusion coefficient (ADC) calculations. The purpose of this study was to separate perfusion and diffusion component based on a biexponential and a segmented monoexponential model using IVIM analysis Methods. The signal attenuation is modeled as S(b) = S0[(1−f)exp(−bD) + fexp(−bD*)]. Fitting the biexponetial decay leads to the quantification of D, the true diffusion coefficient, D*, the pseudodiffusion coefficient, and f, the perfusion fraction. A nonlinear least squares fit and two segmented monoexponential models were used to derive the values for D, D*,‘and f. In the segmented approach b = 200 s/mm{sup 2} was used as the cut-off value for calculation of D. DW-MRI's of a rectum cancer patient were acquired before chemotherapy, before radiation therapy (RT), and 4 weeks into RT and were investigated as an example case. Results: Mean ADC for the tumor drawn on the DWI cases was 0.93, 1.0 and 1.13 10{sup −3}×mm{sup 2}/s before chemotherapy, before RT and 4 weeks into RT. The mean (D.10{sup −3} × mm{sup 2}/s, D* 10{sup −3} × mm{sup 2}/s, and f %) based on biexponential fit was (0.67, 18.6, and 27.2%), (0.72, 17.7, and 28.9%) and (0.83,15.1, and 30.7%) at these time points. The mean (D, D* f) based on segmented fit was (0.72, 10.5, and 12.1%), (0.72, 8.2, and 17.4%) and (.82, 8.1, 16.5%) Conclusion: ADC values are typically higher than true diffusion coefficients. For tumors with significant perfusion effect, ADC should be analyzed at higher b-values or separated from the perfusion component. Biexponential fit overestimates the perfusion fraction because of increased sensitivity to noise at low b-values.

17. ASPECTS (Alberta Stroke Program Early CT Score) Assessment of the Perfusion-Diffusion Mismatch.

PubMed

Lassalle, Louis; Turc, Guillaume; Tisserand, Marie; Charron, Sylvain; Roca, Pauline; Lion, Stephanie; Legrand, Laurence; Edjlali, Myriam; Naggara, Olivier; Meder, Jean-François; Mas, Jean-Louis; Baron, Jean-Claude; Oppenheim, Catherine

2016-10-01

Rapid and reliable assessment of the perfusion-weighted imaging (PWI)/diffusion-weighted imaging (DWI) mismatch is required to promote its wider application in both acute stroke clinical routine and trials. We tested whether an evaluation based on the Alberta Stroke Program Early CT Score (ASPECTS) reliably identifies the PWI/DWI mismatch. A total of 232 consecutive patients with acute middle cerebral artery stroke who underwent pretreatment magnetic resonance imaging (PWI and DWI) were retrospectively evaluated. PWI-ASPECTS and DWI-ASPECTS were determined blind from manually segmented PWI and DWI volumes. Mismatch-ASPECTS was defined as the difference between PWI-ASPECTS and DWI-ASPECTS (a high score indicates a large mismatch). We determined the mismatch-ASPECTS cutoff that best identified the volumetric mismatch, defined as VolumeTmax>6s/VolumeDWI≥1.8, a volume difference≥15 mL, and a VolumeDWI<70 mL. Inter-reader agreement was almost perfect for PWI-ASPECTS (κ=0.95 [95% confidence interval, 0.90-1]), and DWI-ASPECTS (κ=0.96 [95% confidence interval, 0.91-1]). There were strong negative correlations between volumetric and ASPECTS-based assessments of DWI lesions (ρ=-0.84, P<0.01) and PWI lesions (ρ=-0.90, P<0.01). Receiver operating characteristic curve analysis showed that a mismatch-ASPECTS ≥2 best identified a volumetric mismatch, with a sensitivity of 0.93 (95% confidence interval, 0.89-0.98) and a specificity of 0.82 (95% confidence interval, 0.74-0.89). The mismatch-ASPECTS method can detect a true mismatch in patients with acute middle cerebral artery stroke. It could be used for rapid screening of patients with eligible mismatch, in centers not equipped with ultrafast postprocessing software. © 2016 American Heart Association, Inc.

18. Distinction between pyogenic brain abscess and necrotic brain tumour using 3-tesla MR spectroscopy, diffusion and perfusion imaging.

PubMed

Chiang, I-C; Hsieh, T-J; Chiu, M-L; Liu, G-C; Kuo, Y-T; Lin, W-C

2009-10-01

The purpose of this study is to compare the effectiveness of relative cerebral blood volume, apparent diffusion coefficient and spectroscopic imaging in differentiating between cerebral abscesses and necrotic tumours. In the prospective study, a 3-tesla MR unit was used to perform proton MR spectroscopy, diffusion and perfusion imaging in 20 patients with cerebral abscesses and 26 patients who had solitary brain tumours (14 high-grade gliomas and 12 metastases). We found the mean apparent diffusion coefficient value at the central cavities of the cerebral abscesses to be significantly lower than in necrotic tumours. The mean relative cerebral blood volume values of the necrotic tumour wall were statistically significantly higher than the mean relative cerebral blood volume values of the cerebral abscess wall by the Student's t-test. The proton spectra obtained revealed amino acids only in the cerebral abscesses. Although the conventional MRI characteristics of cerebral abscesses and necrotic tumours may sometimes be similar, diffusion, perfusion-weighted and spectroscopic MRI enables distinction between the two.

19. Myocardial function and perfusion in the CREST syndrome variant of progressive systemic sclerosis. Exercise radionuclide evaluation and comparison with diffuse scleroderma

SciTech Connect

Follansbee, W.P.; Curtiss, E.I.; Medsger, T.A. Jr.; Owens, G.R.; Steen, V.D.; Rodnan, G.P.

1984-09-01

Myocardial function and perfusion were evaluated in 22 patients with progressive systemic sclerosis with the CREST syndrome using exercise and radionuclide techniques, pulmonary function testing, and chest roentgenography. The results were compared with a similar study of 26 patients with progressive systemic sclerosis with diffuse scleroderma. The prevalence of thallium perfusion abnormalities was similar in the groups with CREST syndrome and diffuse scleroderma, (64 percent versus 77 percent), but the defects were significantly smaller in the CREST syndrome (p less than 0.01). Reperfusion thallium defects in the absence of extramural coronary artery disease were seen in 38 percent of patients with diffuse scleroderma. This finding was not seen in any of the patients with the CREST syndrome. In diffuse scleroderma, abnormalities of both right and left ventricular function were related to larger thallium perfusion defects. In the CREST syndrome, abnormalities of left ventricular function were minor, were seen only during exercise, and were unrelated to thallium perfusion defects. Abnormal resting right ventricular function was seen in 36 percent of the patients with the CREST syndrome and was associated with an isolated decrease in diffusing capacity of carbon monoxide. It is concluded that the cardiac manifestations of the CREST syndrome are distinct from those found in diffuse scleroderma. Unlike diffuse scleroderma, abnormalities of left ventricular function in the CREST syndrome are minor and are unrelated to abnormalities of coronary perfusion. Right ventricular dysfunction in the CREST syndrome appears to be primarily related to pulmonary vascular disease.

20. Prediction of hemorrhagic transformation following acute stroke: role of diffusion- and perfusion-weighted magnetic resonance imaging.

PubMed

Tong, D C; Adami, A; Moseley, M E; Marks, M P

2001-04-01

Acute diffusion-weighted (DWI) and perfusion-weighted (PWI) magnetic resonance imaging (MRI) findings may correlate with secondary hemorrhagic transformation (HT) risk in patients with stroke. This information could be of value, particularly in individuals being considered for thrombolytic therapy. To determine the relationship between DWI and PWI findings and the risk of secondary HT in patients with acute stroke. Retrospective case series. Academic medical center. Twenty-seven patients with acute stroke capable of being evaluated with DWI/PWI 8 hours or less after symptom onset. Apparent diffusion coefficient values, perfusion delay measurements, and subsequent MRI or computed tomographic scans detected HT. The mean +/- SD apparent diffusion coefficient of ischemic regions that experienced HT was significantly lower than the overall mean +/- SD apparent diffusion coefficient of all ischemic areas analyzed (0.510 +/- 0.140 x 10(-3) mm(2)/s vs 623 +/- 0.113 x 10(-3) mm(2)/s; P =.004). This difference remained significant when comparing the HT-destined ischemic areas with the non-HT-destined areas within the same ischemic lesion (P =.02). Patients receiving recombinant tissue-type plasminogen activator (rt-PA) experienced HT significantly earlier than patients not receiving rt-PA (P =.002). Moreover, a persistent perfusion deficit in the area of subsequent hemorrhage at 3 to 6 hours after the initial MRI scan was identified in significantly more patients who experienced HT than in those who did not (83% vs 30%; P =.03). Both DWI and PWI scans detect abnormalities that are associated with HT. These findings support a role for MRI in identifying patients who are at increased risk for secondary HT following acute ischemic stroke.

1. Comparison of Diffusion Tensor Imaging and Magnetic Resonance Perfusion Imaging in Differentiating Recurrent Brain Neoplasm From Radiation Necrosis.

PubMed

Masch, William R; Wang, Page I; Chenevert, Thomas L; Junck, Larry; Tsien, Christina; Heth, Jason A; Sundgren, Pia C

2016-05-01

2. Perfusion and diffusion limitations in middle ear gas exchange: the exchange of CO2 as a test case.

PubMed

Marcusohn, Yael; Ar, Amos; Dirckx, Joris J J

2010-06-14

A long standing debate on perfusion/diffusion limitations in the context of middle ear (ME) gas exchange was revisited using data obtained from previous iso-pressure gas-exchange measurements in different mammals. We tried to determine whether the exchange of CO(2) in the ME is limited by perfusion or by diffusion by comparing the mass specific cardiac output (msQ) and the mass specific initial CO(2) flow rate into air-washed MEs (msV(i) CO(2)) of rabbits and rats. Based on previously published allometry at rest, the msQ was 0.154 mL/(min g) in rabbits (mean body weight: 2800 g) and 0.259 mL/(min g) in rats (mean body weight: 179.1 g); msV(i) CO(2) (Delta t=0) was 0.109+/-0.047 microL/(h g) in rabbits (n=16) and 0.170+/-0.094 microL/(h g) in rats (n=9). Similar ratios were found when an allometric comparison was made between the ratio of msV(i) CO(2) (Delta t=0) (approximately 0.64), and the ratio of msQs (approximately 0.59) in rabbits and rats. If the active mucosal surface areas of MEs of rabbits and rats are directly proportional to their masses as are the masses of their hearts and if their msQs are proportional to the rates of blood flows in the ME mucosa, these results support the assumption that the exchange of CO(2) in the ME of mammals is mainly perfusion (and not diffusion) dependent.

3. Characterization of stroke lesions using a histogram-based data analysis including diffusion- and perfusion-weighted imaging

Grzesik, Alexander; Bernarding, Johannes; Braun, Juergen; Koennecke, Hans-Christian; Wolf, Karl J.; Tolxdorff, Thomas

2000-04-01

Diffusion- and perfusion-weighted magnetic resonance imaging (DWI, PWI) allows the diagnosis of ischemic brain injury at a time when ischemic lesions may not yet be detectable in computer tomography or T2-weighted (T2w) MRI. However, regions with pathologic apparent diffusion coefficients (ADC) do not necessarily match with regions of prolonged mean transit times (MTT) or pathologic relative cerebral blood flow (rCBF). Mismatching parts are thought to correlate with tissues that can be saved by appropriate treatment. Ten patients with cerebral ischemia underwent standard T1w and T2w imaging as well as single-shot echo planar imaging (EPI) DWI, and PWI. Multidimensional histograms were constructed from T2w images, DWI, ADC, rCBF, and MTT maps. After segmenting different tissues, signal changes of ischemic tissues relative to unaffected parenchyma were calculated. Combining different information allowed the segmentation of lesions and unaffected tissues. Acute infarcts exhibited decreased ADC values as well as hypo- and hyperperfused areas. Correlating ADC, T2w, and rCBF with clinical symptoms allowed the estimation of age and perfusion state of the lesions. Combining DWI, PWI, and standard imaging overcomes strongly fluctuating parameters such as ADC values. A multidimensional parameter-set characterizes unaffected and pathologic tissues which may help in the evaluation of new therapeutic strategies.

4. Endovascular thrombolysis and stenting of a middle cerebral artery occlusion beyond 6 hours post-attack: special reference to the usefulness of diffusion-perfusion MRI.

PubMed

Ahn, Jung Yong; Han, In Bo; Chung, Sang Sup; Chung, Young Sun; Kim, Sang Heum; Yoon, Pyeong Ho

2006-12-01

Intra-arterial thrombolysis and percutaneous angioplasty is feasible in patients with acute middle cerebral artery (MCA) occlusion limited to 6 hours post-ictus, but there are some limitations such as reocclusion or hemorrhagic complications. In this report, we describe a stent placement in the treatment of a refractory artherothrombotic MCA occlusion beyond 6 hours of symptom onset. A 57-year-old man presented with a progressive left-sided weakness and verbal disturbance resulting from an acute thrombotic occlusion of the right MCA superimposed on severe proximal atheromatous stenosis. Diffusion-perfusion magnetic resonance imaging (MRI) demonstrated the significant diffusion-perfusion mismatch. After chemical and mechanical thrombolysis of the clot, balloon angioplasty of the underlying MCA stenosis was performed 2 days post-attack, without significant angiographic improvement. Percutaneous endovascular deployment of a stent (Driver 2.5 x 12 mm, MTI, Irvine, CA) was subsequently performed, with excellent angiographic results. Follow-up diffusion-perfusion MRI showed improved perfusion in the hypoperfused area. The patient's National Institutes of Health Stroke Scale (NIHSS) score was increased from 12 to 3. Clot thrombolysis and subsequent stenting in patients with refractory proximal MCA occlusion is feasible and allows for a significant reduction in the amount of thrombolytic drug required. In selective patients with acute MCA occlusion, the therapeutic window for recanalization procedures can be safely and effectively extended beyond the 'traditional 6 hours'. Diffusion-perfusion MRI in acute MCA occlusion is important for indication of therapy.

5. In vivo cardiac diffusion-weighted magnetic resonance imaging: quantification of normal perfusion and diffusion coefficients with intravoxel incoherent motion imaging.

PubMed

Delattre, Benedicte M A; Viallon, Magalie; Wei, Hongjiang; Zhu, Yuemin M; Feiweier, Thorsten; Pai, Vinay M; Wen, Han; Croisille, Pierre

2012-11-01

Diffusion-weighted imaging (DWI) and the introduction of the intravoxel incoherent motion (IVIM) model have provided a unique method for evaluating perfusion and diffusion within a tissue without the need for a contrast agent. Despite its relevance, cardiac DWI has thus far been limited by low b values because of signal loss induced by physiological motion. The goal of this study was to develop a methodology for estimating IVIM parameters of in vivo cardiac magnetic resonance imaging using an efficient DWI acquisition framework. This was achieved by investigating various acquisition strategies (principal component analysis [PCA] filtering and temporal maximum intensity projection [PCATMIP] and single trigger delay [TD]) and fitting methods. Simulations were performed on a synthetic dataset of diffusion-weighted signal intensity (SI) to determine the fitting method that would yield IVIM parameters with the greatest accuracy. The required number of b values to correctly estimate IVIM parameters was also investigated. Breath-hold DWI scans were performed for 12 volunteers to collect several TD values during diastole. Thirteen b values ranging from 0 to 550 s/mm were used. The IVIM parameters derived using the data from all the acquired TDs (PCATMIP technique) were compared with those derived using a single acquisition performed at an optimized diastolic time point (1TD). The main result of this study was that PCATMIP, when combined with a fitting model that accounted for T1 and T2 relaxation, provided IVIM parameters with less variability. However, an acquisition performed with 1 optimized diastolic TD provided results that were as good as those provided using PCATMIP if the R-R variability during the acquisition was sufficiently low (± 5%). Furthermore, the use of only 9 b values (that could be acquired in 2 breath-holds), instead of 13 b values (requiring 3 breath-holds), was sufficient to determine the IVIM parameters. This study demonstrates that IVIM is

6. Design and testing of diffuse reflectance sensor for continuous monitoring of cutaneous blood perfusion

Zakharov, P.; Talary, M. S.; Caduff, A.

2009-07-01

A dual-wavelength reflectance optical sensor for monitoring cutaneous blood perfusion is presented as a part of multisensor glucose monitoring system. A Monte-Carlo simulation of partial differential pathlengths has been used for the optimization of the distance from light source to detector. The simulation indicated that the light pathlength within the upper vascularised skin layers increases before reaching saturation at separation distances larger than 3 mm. Thus the sensor sensitivity does not benefit from larger source-detector distances. At the same time with a higher separation of the detector from the source, the intensity exponentially decreases while undesirable sensitivity to the muscle perfusion increases. The hardware prototype has been developed based on the simulation findings and tested in a laboratory setting and in a home use study by patients with diabetes. For both testing procedures the optical sensor demonstrated high sensitivity to perfusion changes. The effect of initial cutaneous blood increase under the sensor has been observed which can be associated with pressure-induced vasodilation as a response to the sensor application.

7. Relationship between diffusion parameters derived from intravoxel incoherent motion MRI and perfusion measured by dynamic contrast-enhanced MRI of soft tissue tumors.

PubMed

Marzi, Simona; Stefanetti, Linda; Sperati, Francesca; Anelli, Vincenzo

2016-01-01

Our aim was to evaluate the link between diffusion parameters measured by intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) and the perfusion metrics obtained with dynamic contrast-enhanced (DCE) MRI in soft tissue tumors (STTs). Twenty-eight patients affected by histopathologically confirmed STT were included in a prospective study. All patients underwent both DCE MRI and IVIM DWI. The perfusion fraction f, diffusion coefficient D and perfusion-related diffusion coefficient D* were estimated using a bi-exponential function to fit the DWI data. DCE MRI was acquired with a temporal resolution of 3-5 s. Maps of the initial area under the gadolinium concentration curve (IAUGC), time to peak (TTP) and maximum slope of increase (MSI) were derived using commercial software. The relationships between the DCE MRI and IVIM DWI measurements were assessed by Spearman's test. To exclude false positive results under multiple testing, the false discovery rate (FDR) procedure was applied. The Mann-Whitney test was used to evaluate the differences between all variables in patients with non-myxoid and myxoid STT. No significant relationship was found between IVIM parameters and any DCE MRI parameters. Higher f and D*f values were found in non-myxoid tumors compared with myxoid tumors (p = 0.004 and p = 0.003, respectively). MSI was significantly higher in non-myxoid tumors than in myxoid tumors (p = 0.029). From the visual assessments of single clinical cases, both f and D*f maps were in satisfactory agreement with DCE maps in the extreme cases of an avascular mass and a highly vascularized mass, whereas, for tumors with slight vascularity or with a highly heterogeneous perfusion pattern, this association was not straightforward. Although IVIM DWI was demonstrated to be feasible in STT, our data did not support evident relationships between perfusion-related IVIM parameters and perfusion measured by DCE MRI.

8. The Application of Diffusion- and Perfusion-Weighted Magnetic Resonance Imaging in the Diagnosis and Therapy of Acute Cerebral Infarction

PubMed Central

Li, Enzhong; Tian, Jie; Chen, Jian; Wang, Huifang; Dai, Jianping

2006-01-01

Diffusion- and perfusion-weighted magnetic resonance imaging (DWI and PWI) was applied for stroke diagnose in 120 acute (< 48 h) ischemic stroke patients. At hyperacute (< 6 h) stage, it is difficult to find out the infarction zone in conventional T1 or T2 image, but it is easy in DWI, apparent diffusion coefficient (ADC) map; when at 3–6-hour stage it is also easy in PWI, cerebral blood flow (CBF) map, cerebral blood volume (CBV) map, and mean transit time (MTT) map; at acute (6–48 h) stage, DWI or PWI is more sensitive than conventional T1 or T2 image too. Combining DWI with ADC, acute and chronic infarction can be distinguished. Besides, penumbra which should be developed in meaning was used as an indication or to evaluate the therapeutic efficacy. There were two cases (< 1.5 h) that broke the model of penumbra because abnormity was found in DWI but not that in PWI, finally they recovered without any sequela. PMID:23165020

9. Clarifying nipple confusion.

PubMed

Zimmerman, E; Thompson, K

2015-11-01

Nipple confusion, an infant's difficulty with or preference for one feeding mechanism over another after exposure to artificial nipple(s), has been widely debated. This is in part due to conflicting statements, one by the American Academy of Pediatrics in 2005 suggesting that infants should be given a pacifier to protect against Sudden Infant Death Syndrome, and the other by the World Health Organization in 2009 stating that breastfeeding infants should never be given artificial nipples. Despite the limited and inconsistent evidence, nipple confusion is widely believed by practitioners. Therefore, there is a unique opportunity to examine the evidence surrounding nipple confusion by assessing the research that supports/refutes that bottle feeding/pacifier use impedes breastfeeding efficacy/success/duration. This review examined 14 articles supporting and refuting nipple confusion. These articles were reviewed using the Johns Hopkins Nursing Evidence-Based Practice Rating Scale. Based on our review, we have found emerging evidence to suggest the presence of nipple confusion only as it relates to bottle usage and found very little evidence to support nipple confusion with regards to pacifier use. The primary difficulty in conclusively studying nipple confusion is establishing causality, namely determining whether bottles'/pacifiers' nipples are causing infants to refuse the breast or whether they are simply markers of other maternal/infant characteristics. Future research should focus on prospectively examining the causality of nipple confusion.

10. Multiparametric MR Imaging of Diffusion and Perfusion in Contrast-enhancing and Nonenhancing Components in Patients with Glioblastoma.

PubMed

Boonzaier, Natalie R; Larkin, Timothy J; Matys, Tomasz; van der Hoorn, Anouk; Yan, Jiun-Lin; Price, Stephen J

2017-02-27

Purpose To determine whether regions of low apparent diffusion coefficient (ADC) with high relative cerebral blood volume (rCBV) represented elevated choline (Cho)-to-N-acetylaspartate (NAA) ratio (hereafter, Cho/NAA ratio) and whether their volumes correlated with progression-free survival (PFS) and overall survival (OS) in patients with glioblastoma (GBM). Materials and Methods This retrospective analysis was approved by the local research ethics committee. Volumetric analysis of imaging data from 43 patients with histologically confirmed GBM was performed. Patients underwent preoperative 3-T magnetic resonance imaging with conventional, diffusion-weighted, perfusion-weighted, and spectroscopic sequences. Patients underwent subsequent surgery with adjuvant chemotherapy and radiation therapy. Overlapping low-ADC and high-rCBV regions of interest (ROIs) (hereafter, ADC-rCBV ROIs) were generated in contrast-enhancing and nonenhancing regions. Cho/NAA ratio in ADC-rCBV ROIs was compared with that in control regions by using analysis of variance. All resulting ROI volumes were correlated with patient survival by using multivariate Cox regression. Results ADC-rCBV ROIs within contrast-enhancing and nonenhancing regions showed elevated Cho/NAA ratios, which were significantly higher than those in other abnormal tumor regions (P < .001 and P = .008 for contrast-enhancing and nonenhancing regions, respectively) and in normal-appearing white matter (P < .001 for both contrast-enhancing and nonenhancing regions). After Cox regression analysis controlling for age, tumor size, resection extent, O-6-methylguanine-DNA methyltransferase-methylation, and isocitrate dehydrogenase mutation status, the proportional volume of ADC-rCBV ROIs in nonenhancing regions significantly contributed to multivariate models of OS (hazard ratio, 1.132; P = .026) and PFS (hazard ratio, 1.454; P = .017). Conclusion Volumetric analysis of ADC-rCBV ROIs in nonenhancing regions of GBM can be used to

11. Successful outcome after endovascular thrombolysis for acute ischemic stroke with basis on perfusion-diffusion mismatch after 24 h of symptoms onset

PubMed Central

Mattei, Tobias A.; Rehman, Azeem A.; Goulart, Carlos R.; Sória, Marília G.; Rizelio, Vanessa; Meneses, Murilo S.

2016-01-01

Background: Although intravenous thrombolysis is the Food and Drug Administration-approved treatment for acute ischemic stroke (AIS) within 3 h, combined intravenous and intra-arterial thrombolysis with endovascular techniques may be able to extend this traditional time window. Case Description: We present the clinical evolution of a 45-year-old male presenting with acute left hemiparesis. Magnetic resonance imaging revealed a small diffusion restriction at the right basal ganglia with perfusion compromise in the entire right middle cerebral artery (MCA) territory. Angiography revealed a complete occlusion of MCA at its M1 segment. The patient underwent endovascular mechanical thrombectomy with additional intra-arterial thrombolysis more than 24 hours after the onset of the initial symptoms and experienced complete vessel recanalization. At 1 year, the patient had global independence with minor residual motor impairment in the left arm. Conclusions: We report the case of a successful thrombolytic therapy following AIS performed more than 24 h after the initial symptoms based on the presence of a perfusion-diffusion mismatch. This report is expected to stimulate the development of future prospective studies with special focus on the role of perfusion-diffusion mismatch in patient selection for treatment of AIS, especially in those presenting outside the traditional time window. PMID:27313971

12. Bed-side assessment of cerebral perfusion in stroke patients based on optical monitoring of a dye bolus by time-resolved diffuse reflectance.

PubMed

Liebert, A; Wabnitz, H; Steinbrink, J; Möller, M; Macdonald, R; Rinneberg, H; Villringer, A; Obrig, H

2005-01-15

We present a minimally invasive optical method, that is, multi-channel time-domain diffuse near-infrared reflectometry of the head to assess cerebral blood perfusion that is applicable at the bed-side and repetitively at short intervals. Following intravenous injection of an ICG bolus, its transit through intra- and extracerebral tissue is monitored based on changes in moments of distributions of times of flight of photons, recorded with a 4-channel instrument simultaneously on both hemispheres. In healthy volunteers, we found that variance of distributions of times of flight of photons is well suited to assess latency and initial slope of the increase in absorption of intracerebral tissue due to the bolus. We successfully applied our method in two patients demonstrating a reversible cerebral perfusion deficit in an ischemic stroke patient who was treated by thrombolysis and in another patient with a permanent impaired unilateral perfusion due to ipsilateral internal carotid artery occlusion. In either case, we observed a difference in bolus transit time between the hemispheres. In the stroke patient, this difference resolved when re-evaluated 1 day after thrombolysis. The study demonstrates the necessity of a technique with sub-nanosecond time resolution to allow for depth discrimination if clinical perfusion monitoring of cerebrovascular diseases is addressed by optical methods.

13. Comparison of CT perfusion summary maps to early diffusion-weighted images in suspected acute middle cerebral artery stroke.

PubMed

Benson, John; Payabvash, Seyedmehdi; Salazar, Pascal; Jagadeesan, Bharathi; Palmer, Christopher S; Truwit, Charles L; McKinney, Alexander M

2015-04-01

To assess the accuracy and reliability of one vendor's (Vital Images, Toshiba Medical, Minnetonka, MN) automated CT perfusion (CTP) summary maps in identification and volume estimation of infarcted tissue in patients with acute middle cerebral artery (MCA) distribution infarcts. From 1085 CTP examinations over 5.5 years, 43 diffusion-weighted imaging (DWI)-positive patients were included who underwent both CTP and DWI <12 h after symptom onset, with another 43 age-matched patients as controls (DWI-negative). Automated delay-corrected postprocessing software (DC-SVD) generated both infarct "core only" and "core+penumbra" CTP summary maps. Three reviewers independently tabulated Alberta Stroke Program Early CT scores (ASPECTS) of both CTP summary maps and coregistered DWI. Of 86 included patients, 36 had DWI infarct volumes ≤70 ml, 7 had volumes >70 ml, and 43 were negative; the automated CTP "core only" map correctly classified each as >70 ml or ≤70 ml, while the "core+penumbra" map misclassified 4 as >70 ml. There were strong correlations between DWI volume with both summary map-based volumes: "core only" (r=0.93), and "core+penumbra" (r=0.77) (both p<0.0001). Agreement between ASPECTS scores of infarct core on DWI with summary maps was 0.65-0.74 for "core only" map, and 0.61-0.65 for "core+penumbra" (both p<0.0001). Using DWI-based ASPECTS scores as the standard, the accuracy of the CTP-based maps were 79.1-86.0% for the "core only" map, and 83.7-88.4% for "core+penumbra." Automated CTP summary maps appear to be relatively accurate in both the detection of acute MCA distribution infarcts, and the discrimination of volumes using a 70 ml threshold. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

14. Sensitivity of diffusion- and perfusion-weighted imaging for diagnosing acute ischemic stroke is 97.5%.

PubMed

Simonsen, Claus Z; Madsen, Mette H; Schmitz, Marie L; Mikkelsen, Irene K; Fisher, Marc; Andersen, Grethe

2015-01-01

MRI using diffusion-weighted imaging (DWI) is the most sensitive diagnostic imaging modality for early detection of ischemia, but how accurate is it and how much does perfusion-weighted imaging (PWI) add to the sensitivity have to be known. In this single-center study, we collected epidemiological, imaging, and outcome data on all patients with stroke undergoing MRI-based treatment with intravenous tissue-type plasminogen activator at our center from 2004 to 2010. The DWI negative patients were identified, and we calculated the sensitivity and specificity of DWI and additional PWI for diagnosing acute ischemic stroke. We compared DWI positive and negative patients to identify characteristics associated with DWI negativity. Five hundred sixty-nine consecutive patients were treated with intravenous tissue-type plasminogen activator on the basis of an acute MRI. A DWI lesion was evident in 518 patients. Forty-seven patients were DWI negative; however, a relevant PWI lesion was found in 33 of these patients. Four stroke mimics were treated with intravenous tissue-type plasminogen activator and 1 of these patients had a DWI lesion. Thus, 8% of all patients with stroke were DWI negative. The combination of DWI and PWI resulted in a sensitivity of 97.5% for the ischemic stroke diagnosis. DWI negativity was associated with less severe strokes, location in the posterior circulation, a longer time from onset to scan, and an improved 90-day outcome. The cause of small-vessel disease was more likely to be DWI negative. The combination of DWI and PWI before intravenous tissue-type plasminogen activator confirms the diagnosis in 97.5% of all ischemic strokes. © 2014 American Heart Association, Inc.

15. Spatially resolved diffuse reflectance with laser Doppler imaging for the simultaneous in-vivo measurement of tissue perfusion and metabolic state

Forrester, Kevin R.; Shymkiw, Roxane; Tulip, John; Sutherland, Craig; Hart, David; Bray, Robert C.

2000-06-01

Laser Doppler Imaging (LDI) has become an established technique for the two dimensional measurement of tissue perfusion but the uncertainty of photon penetration depth leads to ambiguous interpretation of what fraction of the tissue microcirculation is being sampled. This study investigates a diffuse reflectance technique for measuring tissue optical properties during LDI perfusion measurement for the simultaneous determination of photon penetration depth and tissue metabolic state. LDI and diffuse reflectance spectroscopy measurements were made on surgically exposed ligaments in pregnant and non-pregnant rabbits. Photon penetration depths are reported. It was observed that anisotropic scattering occurs due to the ordered alignment of collagen fibers within ligament. Tissue perfusion in the ligaments of pregnant animals was significantly lower than in non-pregnant animals. Tissue hemoglobin concentration and oxygenation, and percent vascularization are also reported showing no statistical difference between the ligaments in pregnant and non-pregnant rabbits. A significant difference was observed in the photon scattering coefficient between the pregnant and non-pregnant groups suggesting a change in fibril spacing and/or orientation, most likely caused by an increased laxity in the ligaments of the pregnant animals. These investigations compare well with previous biochemical and biomechanical information obtained on ligaments.

16. Perfusion deficits detected by arterial spin-labeling in patients with TIA with negative diffusion and vascular imaging.

PubMed

Qiao, X J; Salamon, N; Wang, D J J; He, R; Linetsky, M; Ellingson, B M; Pope, W B

2013-01-01

A substantial portion of clinically diagnosed TIA cases is imaging-negative. The purpose of the current study is to determine if arterial spin-labeling is helpful in detecting perfusion abnormalities in patients presenting clinically with TIA. Pseudocontinuous arterial spin-labeling with 3D background-suppressed gradient and spin-echo was acquired on 49 patients suspected of TIA within 24 hours of symptom onset. All patients were free of stroke history and had no lesion-specific findings on general MR, DWI, and MRA sequences. The calculated arterial spin-labeling CBF maps were scored from 1-3 on the basis of presence and severity of perfusion disturbance by 3 independent observers blinded to patient history. An age-matched cohort of 36 patients diagnosed with no cerebrovascular events was evaluated as a control. Interobserver agreement was assessed by use of the Kendall concordance test. Scoring of perfusion abnormalities on arterial spin-labeling scans of the TIA cohort was highly concordant among the 3 observers (W = 0.812). The sensitivity and specificity of arterial spin-labeling in the diagnosis of perfusion abnormalities in TIA was 55.8% and 90.7%, respectively. In 93.3% (70/75) of the arterial spin-labeling CBF map readings with positive scores (≥2), the brain regions where perfusion abnormalities were identified by 3 observers matched with the neurologic deficits at TIA onset. In this preliminary study, arterial spin-labeling showed promise in the detection of perfusion abnormalities that correlated with clinically diagnosed TIA in patients with otherwise normal neuroimaging results.

17. Spatiotemporal Dynamic Simulation of Acute Perfusion/Diffusion Ischemic Stroke Lesions Evolution: A Pilot Study Derived from Longitudinal MR Patient Data

PubMed Central

Rekik, Islem; Allassonnière, Stéphanie; Durrleman, Stanley; Carpenter, Trevor; Wardlaw, Joanna

2013-01-01

The spatiotemporal evolution of stroke lesions, from acute injury to final tissue damage, is complex. Diffusion-weighted (DWI) and perfusion-weighted (PWI) imaging is commonly used to detect early ischemic changes and attempts to distinguish between permanently damaged and salvageable tissues. To date, 2D and 3D measures of diffusion/perfusion regions at individual timepoints have been widely used but may underestimate the true lesion spatio-temporal dynamics. Currently there is no spatio-temporal 4D dynamic model that simulates the continuous evolution of ischemic stroke from MR images. We determined whether a 4D current-based diffeomorphic model, developed in the field of statistical modeling for measuring the variability of anatomical surfaces, could estimate patient-specific spatio-temporal continuous evolution for MR PWI (measured as mean transit time, (MTT)) and DWI lesions. In our representative pilot sample, the model fitted the data well. Our dynamic analysis of lesion evolution showed different patterns; for example, some DWI/PWI dynamic changes corresponded with DWI lesion expansion into PWI lesions, but other patterns were much more complex and diverse. There was wide variation in the time when the final tissue damage was reached after stroke for DWI and MTT. PMID:23853669

18. Investigating potentially salvageable penumbra tissue in an in vivo model of transient ischemic stroke using sodium, diffusion, and perfusion magnetic resonance imaging.

PubMed

Wetterling, Friedrich; Chatzikonstantinou, Eva; Tritschler, Laurent; Meairs, Stephen; Fatar, Marc; Schad, Lothar R; Ansar, Saema

2016-12-07

Diffusion magnetic resonance imaging (MRI) is the current-state-of-the-art technique to clinically investigate acute (0-24 h) ischemic stroke tissue. However, reduced apparent diffusion coefficient (ADC)-considered a marker of tissue damage-was observed to reverse spontaneously during the subacute stroke phase (24-72 h) which means that low ADC cannot be used to reflect the damaged tissue after 24 h in experimental and clinical studies. One reason for the change in ADC is that ADC values drop with cytotoxic edema (acute phase) and rise when vasogenic edema begins (subacute phase). Recently, combined (1)H- and (23)Na-MRI was proposed as a more accurate approach to improve delineation between reversible (penumbra) and irreversible ischemic injury (core). The aim of this study was to investigate the effects of reperfusion on the ADC and the sodium MRI signal after experimental ischemic stroke in rats in well-defined areas of different viability levels of the cerebral lesion, i.e. core and penumbra as defined via perfusion and histology. Transient middle cerebral artery occlusion was induced in male rats by using the intraluminal filament technique. MRI sodium, perfusion and diffusion measurement was recorded before reperfusion, shortly after reperfusion and 24 h after reperfusion. The animals were reperfused after 90 min of ischemia. Sodium signal in core did not change before reperfusion, increased after reperfusion while sodium signal in penumbra was significantly reduced before reperfusion, but showed no changes after reperfusion compared to control. The ADC was significantly decreased in core tissue at all three time points compared to contralateral side. This decrease recovered above commonly applied viability thresholds in the core after 24 h. Reduced sodium-MRI signal in conjunction with reduced ADC can serve as a viability marker for penumbra detection and complement hydrogen diffusion- and perfusion-MRI in order to facilitate time-independent assessment

19. A compartment model of alveolar-capillary oxygen diffusion with ventilation-perfusion gradient and dynamics of air transport through the respiratory tract.

PubMed

Jaworski, Jacek; Redlarski, Grzegorz

2014-08-01

This paper presents a model of alveolar-capillary oxygen diffusion with dynamics of air transport through the respiratory tract. For this purpose electrical model representing the respiratory tract mechanics and differential equations representing oxygen membrane diffusion are combined. Relevant thermodynamic relations describing the mass of oxygen transported into the human body are proposed as the connection between these models, as well as the influence of ventilation-perfusion mismatch on the oxygen diffusion. The model is verified based on simulation results of varying exercise intensities and statistical calculations of the results obtained during various clinical trials. The benefit of the approach proposed is its application in simulation-based research aimed to generate quantitative data of normal and pathological conditions. Based on the model presented, taking into account many essential physiological processes and air transport dynamics, comprehensive and combined studies of the respiratory efficiency can be performed. The impact of physical exercise, precise changes in respiratory tract mechanics and alterations in breathing pattern can be analyzed together with the impact of various changes in alveolar-capillary oxygen diffusion. This may be useful in simulation of effects of many severe medical conditions and increased activity level.

20. Dynamic Susceptibility Contrast Perfusion-Weighted Magnetic Resonance Imaging and Diffusion-Weighted Magnetic Resonance Imaging in Differentiating Recurrent Head and Neck Cancer From Postradiation Changes.

PubMed

2015-01-01

1. Quantitative myocardial perfusion SPECT.

PubMed

Tsui, B M; Frey, E C; LaCroix, K J; Lalush, D S; McCartney, W H; King, M A; Gullberg, G T

1998-01-01

In recent years, there has been much interest in the clinical application of attenuation compensation to myocardial perfusion single photon emission computed tomography (SPECT) with the promise that accurate quantitative images can be obtained to improve clinical diagnoses. The different attenuation compensation methods that are available create confusion and some misconceptions. Also, attenuation-compensated images reveal other image-degrading effects including collimator-detector blurring and scatter that are not apparent in uncompensated images. This article presents basic concepts of the major factors that degrade the quality and quantitative accuracy of myocardial perfusion SPECT images, and includes a discussion of the various image reconstruction and compensation methods and misconceptions and pitfalls in implementation. The differences between the various compensation methods and their performance are demonstrated. Particular emphasis is directed to an approach that promises to provide quantitative myocardial perfusion SPECT images by accurately compensating for the 3-dimensional (3-D) attenuation, collimator-detector response, and scatter effects. With advances in the computer hardware and optimized implementation techniques, quantitatively accurate and high-quality myocardial perfusion SPECT images can be obtained in clinically acceptable processing time. Examples from simulation, phantom, and patient studies are used to demonstrate the various aspects of the investigation. We conclude that quantitative myocardial perfusion SPECT, which holds great promise to improve clinical diagnosis, is an achievable goal in the near future.

2. Current concepts on magnetic resonance imaging (MRI) perfusion-diffusion assessment in acute ischaemic stroke: a review & an update for the clinicians

PubMed Central

2014-01-01

Recently, several medical societies published joint statements about imaging recommendations for acute stroke and transient ischaemic attack patients. In following with these published guidelines, we considered it appropriate to present a brief, practical and updated review of the most relevant concepts on the MRI assessment of acute stroke. Basic principles of the clinical interpretation of diffusion, perfusion, and MRI angiography (as part of a global MRI protocol) are discussed with accompanying images for each sequence. Brief comments on incidence and differential diagnosis are also included, together with limitations of the techniques and levels of evidence. The purpose of this article is to present knowledge that can be applied in day-to-day clinical practice in specialized stroke units or emergency rooms to attend patients with acute ischaemic stroke or transient ischaemic attack according to international standards. PMID:25758570

3. 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

4. Combined Diffusion and Perfusion MR Imaging as Biomarkers of Prognosis in Immunocompetent Patients with Primary Central Nervous System Lymphoma

PubMed Central

Valles, F.E.; Perez-Valles, C.L.; Regalado, S.; Barajas, R.F.; Rubenstein, J.L.; Cha, S.

2014-01-01

5. Diffusion, perfusion and the exclusion principles in the structural and functional organization of the living cell: reappraisal of the properties of the 'ground substance'.

PubMed

Wheatley, Denys N

2003-06-01

The thesis is presented that only within very small microdomains of the cell internum might diffusion operate in the sorting of molecular affinities. Much of cell metabolism is guided and controlled in rate by the speed with which molecules that have to interact encounter one another. What is clear, however, is that the cell does not have a single 'modus operandi' but has the choice of many different strategies, each of which can contribute in different proportion to the rate of ongoing activity. It is probably our own desire to simplify things and use the most (or more) probable strategy that confines our appreciation of the overall robustness of the cell as a 'survival machine'. The main operative process at any given time (perfusion, diffusion or whatever) has always to be considered very carefully in relation to the organisational structure of the cell, which can be transient and fickle but nevertheless has been seen as involving an extensive cytomatrix, a ground substance, within an aqueous environment in which the degree of water structuring is even more fickle.

6. The role of magnetic resonance diffusion-weighted imaging and three-dimensional arterial spin labelling perfusion imaging in the differentiation of parasellar meningioma and cavernous haemangioma.

PubMed

Xiao, Hua-Feng; Lou, Xin; Liu, Meng-Yu; Wang, Yu-Lin; Wang, Yan; Chen, Zhi-Ye; Shi, Kai-Ning; Ma, Lin

2014-08-01

To evaluate the diagnostic value of magnetic resonance diffusion-weighted imaging (DWI) and three-dimensional arterial spin labelling perfusion imaging (3D-ASL) in distinguishing cavernous haemangioma from parasellar meningioma, using histological data as a reference standard. Patients with parasellar meningioma or parasellar cavernous haemangioma underwent conventional T1- and T2-weighted magnetic resonance imaging (MRI) followed by DWI and 3D-ASL using a 3.0 Tesla MRI. The minimum apparent diffusion coefficient (minADC) from DWI and the maximal normalized cerebral blood flow (nCBF) from 3D-ASL were measured in each tumour. Diagnosis was confirmed by histology. MinADC was significantly lower and nCBF significantly higher in meningioma (n = 19) than cavernous haemangioma (n = 15). There was a significant negative correlation between minADC and nCBF (r = -0.605). DWI and 3D-ASL are useful in differentiating cavernous haemangiomas from parasellar meningiomas, particularly in situations when the appearance on conventional MRI sequences is otherwise ambiguous. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

7. The benefits of getting confused

Cotton, Charles

2017-07-01

Getting confused (in lessons) is not necessarily a bad thing. In some physics lessons it may well be inevitable. Understanding may or may not be possible but thinking it through will always help, and this how learning takes place. Confusion need not be a bad thing!

8. The role of diffusion and perfusion weighted imaging in the differential diagnosis of cerebral tumors: a review and future perspectives

PubMed Central

2014-01-01

The role of conventional Magnetic Resonance Imaging (MRI) in the detection of cerebral tumors has been well established. However its excellent soft tissue visualization and variety of imaging sequences are in many cases non-specific for the assessment of brain tumor grading. Hence, advanced MRI techniques, like Diffusion-Weighted Imaging (DWI), Diffusion Tensor Imaging (DTI) and Dynamic-Susceptibility Contrast Imaging (DSCI), which are based on different contrast principles, have been used in the clinical routine to improve diagnostic accuracy. The variety of quantitative information derived from these techniques provides significant structural and functional information in a cellular level, highlighting aspects of the underlying brain pathophysiology. The present work, reviews physical principles and recent results obtained using DWI/DTI and DSCI, in tumor characterization and grading of the most common cerebral neoplasms, and discusses how the available MR quantitative data can be utilized through advanced methods of analysis, in order to optimize clinical decision making. PMID:25609475

9. Liver metastases from colorectal cancer treated with conventional and antiangiogenetic chemotherapy: evaluation with liver computed tomography perfusion and magnetic resonance diffusion-weighted imaging.

PubMed

Anzidei, Michele; Napoli, Alessandro; Zaccagna, Fulvio; Cartocci, Gaia; Saba, Luca; Menichini, Guendalina; Cavallo Marincola, Beatrice; Marincola, Beatrice Cavallo; Marotta, Eugenio; Di Mare, Luisa; Catalano, Carlo; Passariello, Roberto

2011-01-01

The objectives of the study were to determine whether perfusion computed tomography (CT-p) and magnetic resonance diffusion-weighted imaging (MR-DWI) can allow evaluation of the effects of chemotherapy combined with antiangiogenetic treatment on liver metastases in patients with advanced colorectal cancer and to determine if changes in CT-p and MR-DWI correlate with the response to therapy as assessed by conventional Response Evaluation Criteria in Solid Tumors (RECIST). Eighteen patients with liver metastases from colorectal cancer underwent CT-p and MR-DWI before and 6 months after chemotherapy and antiangiogenetic treatment. Lesions were classified according to RECIST criteria (complete response [CR], partial response [PR], stable disease [SD], and progressive disease) and calculations of CT-p parameters including blood flow (BF), blood volume (BV), capillary permeability (CP), and MR-DWI apparent diffusion coefficient (ADC) values were performed; RECIST, CT-p, and MR-DWI measurements at baseline and follow-up were tested for statistically significant differences using the paired-samples t test. Baseline and follow-up perfusion parameters of the lesions were also compared on the basis of therapy response assessed by RECIST criteria using independent-samples t test. P < 0.05 was considered indicative of a statistically significant difference for all statistical test. Six patients (6/18; 33.3%) were classified as PR (), and the remaining 12 (12/18; 66.7%) were classified as SD. On a per-lesion basis, 2 (2/32; 6.3%) cannot be identified at follow-up, 6 (6/32; 18.8%) showed a decrease in size of more than 30%, and 24 (24/32; 75%) were substantially stable in size. No cases of progressive disease were demonstrated at follow-up. No statistically significant differences were demonstrated between PR, CR, and SD lesions for BF (P = 0.19), BV (P = 0.14), and ADC (P = 0.68) measurements, whereas CP was significantly higher in CR and PR lesions (P = 0.038). Considering

10. [The evaluation of cerebral function by diffusion weighted imaging after norepinephrine-induced hypertensive perfusion therapy in pig model of cardiac arrest].

PubMed

Su, Zhi-yu; Li, Chun-sheng

2013-02-01

To evaluate the changes in cerebral function of pigs with cardiac arrest (CA) after recovery of spontaneous circulation (ROSC) after hypertension perfusion therapy induced by norepinephrine (NE). Ventricular fibrillation (VF) was induced by electrical stimulation, and standard cardiopulmonary resuscitation (CPR) was performed after VF for 4 minutes. The pigs with successful ROSC were randomly divided into two group, each n=5. The pigs in the hypertensive reperfusion group were given with NE immediately to maintain the mean arterial pressure (MAP) at 130% before VF for 4 hours; MAP of the pigs in normal reperfusion group was maintained for 4 hours as baseline. The changes in hemodynamics were observed for 4 hours in both groups. Cerebral cortex was scanned with diffusion weighted imaging (DWI) before VF and 1 hour and 3 hours after ROSC, and the dynamic changes in brain functional imaging were observed. Twenty-four hours after ROSC, brain biopsy were collected and examined after hematoxylin and eosin staining (HE). Compared with the normal reperfusion group, heart rate (HR), MAP, cardiac output (CO) and coronary perfusion pressure (CPP) in the hypertensive reperfusion group showed a tendency to increase (ROSC 30 minutes HR: 167±8 bpm vs. 140±15 bpm, ROSC 1 hour MAP: 131±9 mm Hg vs. 108±10 mm Hg, ROSC 1 hour CO: 4.9±0.1 L/min vs. 3.4±0.5 L/min, ROSC 2 hours CPP: 118±12 mm Hg vs. 88±1 mm Hg, P<0.05 or P<0.01). There was no obvious abnormality as shown by DWI before and after resuscitation, and the apparent diffusion coefficient (ADC) showed a tendency to decrease after resuscitation in both groups. The ADC in the normal reperfusion group was decreased more than that in the hypertensive reperfusion. Pathological study showed that the protective effect of the hypertensive reperfusion on brain tissue was better than that of the normal reperfusion group. Hypertensive reperfusion can produce hemodynamic changes, and an increase in cerebral blood flow, thus it

11. The Disconnection Hypothesis in Alzheimer's Disease Studied Through Multimodal Magnetic Resonance Imaging: Structural, Perfusion, and Diffusion Tensor Imaging.

PubMed

Lacalle-Aurioles, María; Navas-Sánchez, Francisco Javier; Alemán-Gómez, Yasser; Olazarán, Javier; Guzmán-De-Villoria, Juan Adán; Cruz-Orduña, Isabel; Mateos-Pérez, José María; Desco, Manuel

2016-01-01

According to the so-called disconnection hypothesis, the loss of synaptic inputs from the medial temporal lobes (MTL) in Alzheimer's disease (AD) may lead to reduced activity of target neurons in cortical areas and, consequently, to decreased cerebral blood flow (CBF) in those areas. The aim of this study was to assess whether hypoperfusion in parietotemporal and frontal cortices of patients with mild cognitive impairment who converted to AD (MCI-c) and patients with mild AD is associated with atrophy in the MTL and/or microstructural changes in the white matter (WM) tracts connecting these areas. We assessed these relationships by investigating correlations between CBF in hypoperfused areas, mean cortical thickness in atrophied regions of the MTL, and fractional anisotropy (FA) in WM tracts. In the MCI-c group, a strong correlation was observed between CBF of the superior parietal gyri and FA in the parahippocampal tracts (left: r = 0.90, p <  0.0001; right: r = 0.597, p = 0.024), and between FA in the right parahippocampal tract and the right precuneus (r = 0.551, p = 0.041). No significant correlations between CBF in hypoperfused regions and FA in the WM tract were observed in the AD group. These results suggest an association between perfusion deficits and altered WM tracts in prodromal AD, while microvasculature impairments may have a greater influence in more advanced stages. We did not find correlations between cortical thinning in the medial temporal lobes and decreased FA in the WM tracts of the limbic system in either group.

12. Sundowning: Late-Day Confusion

MedlinePlus

... behavior is unknown. Factors that may aggravate late-day confusion include: Fatigue Low lighting Increased shadows Disruption ... for activities and exposure to light during the day to encourage nighttime sleepiness. Limit daytime napping. Limit ...

13. A hybrid microfluidic platform for cell-based assays via diffusive and convective trans-membrane perfusion

PubMed Central

Vereshchagina, Elizaveta; Mc Glade, Declan; Glynn, Macdara; Ducrée, Jens

2013-01-01

We present a novel 3D hybrid assembly of a polymer microfluidic chip with polycarbonate track-etched membrane (PCTEM) enabling membrane-supported cell culture. Two chip designs have been developed to establish either diffusive or convective reagent delivery using the integrated PCTEM. While it is well suited to a range of cell-based assays, we specifically employ this platform for the screening of a common antitumor chemotoxic agent (mitomycin C – MMC) on the HL60 myeloid leukemia cell line. The toxic activity of MMC is based on the generation of severe DNA damage in the cells. Using either mode of operation, the HL60 cells were cultured on-chip before, during, and after exposure to MMC at concentrations ranging from 0 to 50 μM. Cell viability was analysed off-chip by the trypan blue dye exclusion assay. The results of the on-chip viability assay were found to be consistent with those obtained off-chip and indicated ca. 40% cell survival at MMC concentration of 50 μM. The catalogue of capabilities of the here described cell assay platform comprises of (i) the culturing of cells either under shear-free conditions or under induced through-membrane flows, (ii) the tight time control of the reagent exposure, (iii) the straightforward assembly of devices, (iv) the flexibility on the choice of the membrane, and, prospectively, (v) the amenability for large-scale parallelization. PMID:24404021

14. Predictive values of diffusion-weighted imaging and perfusion-weighted imaging in evaluating the efficacy of transcatheter arterial chemoembolization for hepatocellular carcinoma

PubMed Central

Lin, Min; Tian, Man-Man; Zhang, Wei-Ping; Xu, Li; Jin, Ping

2016-01-01

This study explored the predictive values of diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) in evaluating the efficacy of transcatheter arterial chemoembolization (TACE) for patients with hepatocellular carcinoma (HCC). A total of 118 HCC patients treated with TACE were selected from April 2013 to November 2015. T1-weighted imaging (T1WI)/T2-weighted imaging (T2WI), DWI, and PWI were performed on all patients before and after TACE. Efficacy was evaluated according to modified Response Evaluation Criteria in Solid Tumors 1.1. Receiver operating characteristic curve was used to evaluate the diagnostic power of quantitative DWI and PWI parameters in evaluating the efficacy of TACE for HCC patients. Among the 118 HCC patients, there were 17 cases (14.4%) with complete response, 50 cases (42.4%) with partial response, 28 cases (23.7%) with stable disease, and 23 cases (19.5%) with progressive disease. There were 67 patients in the effective group (complete response + partial response) and 51 patients in the ineffective group (stable disease + progressive disease). Before TACE, there were significant differences in maximum tumor diameter (MTD), apparent diffusion coefficient (ADC), slow ADC (Dslow), fast ADC (Dfast), transfer constant of vessel at the maximum level (Ktrans), and rate constant of backflux (Kep) between the effective and ineffective groups (all P<0.05). After TACE, the effective group exhibited lower MTD, Dfast, and Kep and higher ADC and Dslow than the ineffective group (all P<0.05). Tumor regression rate negatively correlated with MTD, Ktrans, Kep, and Dfast but positively correlated with ADC and Dslow. Receiver operating characteristic curve analysis suggested that the area under the curve of ADC, Dslow, Dfast, Ktrans, and Kep were 0.869, 0.833, 0.812, 0.802, and 0.809, respectively. In conclusion, these results suggest that quantitative DWI and PWI parameters might be useful in evaluating the efficacy of TACE in the treatment of

15. Confused Resident Care. Instructor Guide.

ERIC Educational Resources Information Center

Missouri Univ., Columbia. Instructional Materials Lab.

This instructional module was designed for certified nurse assistants (CNA). This voluntary training program was developed as a "continuing education" option for the practicing graduate CNA with the intention of providing CNAs with the requisite knowledge and skills to provide care for the confused elderly resident in a long-term care…

16. Confusion and altered behaviour? Cause

PubMed Central

Lobo, Ronstan; Pillay, Isweri; Kennedy, Barry; Watts, Michael

2013-01-01

We describe the case of a 65-year-old man who presented with confusion and change in behaviour, and describe the investigative steps that were taken before a diagnosis was made. This patient was eventually diagnosed with leptomeningeal carcinomatosis secondary to a previously undiagnosed oesophageal carcinoma. PMID:23341584

17. The Confusing Expectations for Education.

ERIC Educational Resources Information Center

Farquhar, Robin H.

Frequently, the expectations placed on education can lead to confusion over its mission. How one college president, at career end, views the purpose of education is presented in this address. The paper details how educators have tried to meet myriad demands in the face of eroding social support systems, claiming that educators must limit their…

18. Confusion

MedlinePlus

... imbalance Illness in an older person, such as loss of brain function ( dementia ) Illness in a person with existing neurological disease, such as a stroke Infections Lack of sleep (sleep deprivation) Low blood sugar Low levels of oxygen (for ...

19. Concussion is confusing us all

PubMed Central

Sharp, David J

2015-01-01

It is time to stop using the term concussion as it has no clear definition and no pathological meaning. This confusion is increasingly problematic as the management of ‘concussed’ individuals is a pressing concern. Historically, it has been used to describe patients briefly disabled following a head injury, with the assumption that this was due to a transient disorder of brain function without long-term sequelae. However, the symptoms of concussion are highly variable in duration, and can persist for many years with no reliable early predictors of outcome. Using vague terminology for post-traumatic problems leads to misconceptions and biases in the diagnostic process, producing uninterpretable science, poor clinical guidelines and confused policy. We propose that the term concussion should be avoided. Instead neurologists and other healthcare professionals should classify the severity of traumatic brain injury and then attempt to precisely diagnose the underlying cause of post-traumatic symptoms. PMID:25977270

20. Perfusion CT improves diagnostic accuracy for hyperacute ischemic stroke in the 3-hour window: study of 100 patients with diffusion MRI confirmation.

PubMed

Lin, Ke; Do, Kinh G; Ong, Phat; Shapiro, Maksim; Babb, James S; Siller, Keith A; Pramanik, Bidyut K

2009-01-01

Conventional noncontrast CT (NCCT) is insensitive to hyperacute cerebral infarction in the first 3 h. Our aim was to determine if CT perfusion (CTP) can improve diagnostic accuracy over NCCT for patients presenting with stroke symptoms in the 3-hour window. Consecutive patients presenting to our emergency department with symptoms of ischemic stroke <3 h old and receiving NCCT and CTP as part of their triage evaluation were retrospectively reviewed. Patients with follow-up diffusion-weighted MRI (DWI) <7 days from ictus were included. Two readers rated the NCCT and CTP for evidence of acute infarct and its vascular territory. CTP selectively covered 24 mm of brain centered at the basal ganglia with low relative cerebral blood volume in a region of low cerebral blood flow or elevated time to peak as the operational definition for infarction. A third reader rated all follow-up DWI for acute infarct and its vascular territory as the reference standard. Sensitivity, specificity, and predictive values were calculated. An exact McNemar test and generalized estimating equations from a binary logistic regression model were used to assess the difference in detection rates between modalities. A two-sided p value <0.05 was considered significant. 100 patients were included. Sixty-five (65%) patients had follow-up DWI confirmation of acute infarct. NCCT revealed 17 (26.2%) acute infarcts without false positives. CTP revealed 42 (64.6%) acute infarcts with one false positive. Of the 23 infarcts missed on CTP, 10 (43.5%) were outside the volume of coverage while the remaining 13 (56.5%) were small cortical or lacunar type infarcts (

1. 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

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

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

2015-10-01

3. Perfusion abnormalities in hemimegalencephaly.

PubMed

Wintermark, P; Roulet-Perez, E; Maeder-Ingvar, M; Moessinger, A C; Gudinchet, F; Meuli, R

2009-04-01

Cerebrovascular changes are rarely discussed in patients with hemimegalencephaly. These alterations have previously been associated with epileptical activity. We report the case of a 36-week gestation neonate presenting with total right hemimegalencephaly, as demonstrated by a magnetic resonance imaging (MRI) performed in the first days of life. Perfusion-weighted imaging displayed a clear hypervascularization of the right hemisphere. Diffusion-tensor imaging showed an arrangement of white matter fibers concentrically around the ventricle on the right hemisphere. AngioMRI showed an obvious asymmetry in the size of the middle cerebral arteries, with the right middle cerebral artery being prominent. The baby was free of clinical seizures during his first week of life. An electroencephalogram at that time displayed an asymmetric background activity, but no electrical seizures. Perfusion anomalies in hemimegalencephaly may not necessarily be related to epileptical activity, but may be related to vessel alterations. (c) Georg Thieme Verlag KG Stuttgart, New York.

4. Concussion is confusing us all.

PubMed

Sharp, David J; Jenkins, Peter O

2015-06-01

It is time to stop using the term concussion as it has no clear definition and no pathological meaning. This confusion is increasingly problematic as the management of 'concussed' individuals is a pressing concern. Historically, it has been used to describe patients briefly disabled following a head injury, with the assumption that this was due to a transient disorder of brain function without long-term sequelae. However, the symptoms of concussion are highly variable in duration, and can persist for many years with no reliable early predictors of outcome. Using vague terminology for post-traumatic problems leads to misconceptions and biases in the diagnostic process, producing uninterpretable science, poor clinical guidelines and confused policy. We propose that the term concussion should be avoided. Instead neurologists and other healthcare professionals should classify the severity of traumatic brain injury and then attempt to precisely diagnose the underlying cause of post-traumatic symptoms. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

5. In Acute Stroke, Can CT Perfusion-Derived Cerebral Blood Volume Maps Substitute for Diffusion-Weighted Imaging in Identifying the Ischemic Core?

PubMed Central

Copen, William A.; Morais, Livia T.; Wu, Ona; Schwamm, Lee H.; Schaefer, Pamela W.; González, R. Gilberto; Yoo, Albert J.

2015-01-01

Background and Purpose In the treatment of patients with suspected acute ischemic stroke, increasing evidence suggests the importance of measuring the volume of the irreversibly injured “ischemic core.” The gold standard method for doing this in the clinical setting is diffusion-weighted magnetic resonance imaging (DWI), but many authors suggest that maps of regional cerebral blood volume (CBV) derived from computed tomography perfusion imaging (CTP) can substitute for DWI. We sought to determine whether DWI and CTP-derived CBV maps are equivalent in measuring core volume. Methods 58 patients with suspected stroke underwent CTP and DWI within 6 hours of symptom onset. We measured low-CBV lesion volumes using three methods: “objective absolute,” i.e. the volume of tissue with CBV below each of six published absolute thresholds (0.9–2.5 mL/100 g), “objective relative,” whose six thresholds (51%-60%) were fractions of mean contralateral CBV, and “subjective,” in which two radiologists (R1, R2) outlined lesions subjectively. We assessed the sensitivity and specificity of each method, threshold, and radiologist in detecting infarction, and the degree to which each over- or underestimated the DWI core volume. Additionally, in the subset of 32 patients for whom follow-up CT or MRI was available, we measured the proportion of CBV- or DWI-defined core lesions that exceeded the follow-up infarct volume, and the maximum amount by which this occurred. Results DWI was positive in 72% (42/58) of patients. CBV maps’ sensitivity/specificity in identifying DWI-positive patients were 100%/0% for both objective methods with all thresholds, 43%/94% for R1, and 83%/44% for R2. Mean core overestimation was 156–699 mL for objective absolute thresholds, and 127–200 mL for objective relative thresholds. For R1 and R2, respectively, mean±SD subjective overestimation were -11±26 mL and -11±23 mL, but subjective volumes differed from DWI volumes by up to 117 and 124

6. Core Knowledge Confusions Among University Students

Lindeman, Marjaana; Svedholm, Annika M.; Takada, Mikito; Lönnqvist, Jan-Erik; Verkasalo, Markku

2011-05-01

Previous studies have demonstrated that university students hold several paranormal beliefs and that paranormal beliefs can be best explained with core knowledge confusions. The aim of this study was to explore to what extent university students confuse the core ontological attributes of lifeless material objects (e.g. a house, a stone), living organisms (e.g. plants), and mental states (e.g., thoughts); whether some core knowledge confusions are more common than others; whether the confusions differ between students from different fields of study, and to replicate the finding that paranormal beliefs increase together with core knowledge confusions. The results showed that half of the participants considered at least four, and one quarter of the participants considered 8-30 confusion statements to be literally true and that the confusions were strongly and positively associated with the amount of paranormal beliefs. The findings indicate that university education does not abolish the misconceptions that characterize children's thinking.

7. Analyzing phonetic confusions using formal concept analysis.

PubMed

Peláez-Moreno, C; García-Moral, A I; Valverde-Albacete, F J

2010-09-01

Confusion matrices have been used as a tool for the analysis of speech perception or human speech recognition (HSR) for decades. However, they are rarely employed in automatic speech recognition (ASR) mainly due to the lack of a systematic procedure for their exploration. The generalization of formal concept analysis employed in this paper provides a conceptual interpretation of confusion matrices that enables the analysis of the structure of confusions for both human and machine performances. Generalized formal concept analysis transforms confusion matrices into ordered lattices of confusion events, supporting classic results in HSR that identify a hierarchy of virtual articulatory-acoustic channels. Translating this technique into ASR, a detailed map of the relationships among the speech units employed in the system can be traced to make different sources of confusions apparent: the influence of the lexicon, segmentation errors, dialectal variations or limitations of the feature extraction procedures, among others.

8. Homosexuality: coming out of the confusion.

PubMed

Phillips, Sidney H

2003-12-01

The author asserts that earlier theoretical assumptions contribute to the conceptual confusion about homosexuality in much contemporary psychoanalytic research. Bergeret's article, recently published in this Journal, is exemplary of this confusion. The author refutes his contention that homosexuality is not 'true' sexuality but merely a defensive, narcissistic fixation away from, or a nearly psychotic denial of, heterosexuality. He then clarifies specific areas of conceptual confusion regarding homosexuality still prevalent in psychoanalytic discourse that derive from earlier theoretical premises. These areas of confusion include manifest versus latent homosexuality, narcissism and bisexuality, oedipal dynamics and development, and transference and technique.

9. A semi-automated measuring system of brain diffusion and perfusion magnetic resonance imaging abnormalities in patients with multiple sclerosis based on the integration of coregistration and tissue segmentation procedures.

PubMed

Revenaz, Alfredo; Ruggeri, Massimiliano; Laganà, Marcella; Bergsland, Niels; Groppo, Elisabetta; Rovaris, Marco; Fainardi, Enrico

2016-01-14

Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) abnormalities in patients with multiple sclerosis (MS) are currently measured by a complex combination of separate procedures. Therefore, the purpose of this study was to provide a reliable method for reducing analysis complexity and obtaining reproducible results. We implemented a semi-automated measuring system in which different well-known software components for magnetic resonance imaging (MRI) analysis are integrated to obtain reliable measurements of DWI and PWI disturbances in MS. We generated the Diffusion/Perfusion Project (DPP) Suite, in which a series of external software programs are managed and harmonically and hierarchically incorporated by in-house developed Matlab software to perform the following processes: 1) image pre-processing, including imaging data anonymization and conversion from DICOM to Nifti format; 2) co-registration of 2D and 3D non-enhanced and Gd-enhanced T1-weighted images in fluid-attenuated inversion recovery (FLAIR) space; 3) lesion segmentation and classification, in which FLAIR lesions are at first segmented and then categorized according to their presumed evolution; 4) co-registration of segmented FLAIR lesion in T1 space to obtain the FLAIR lesion mask in the T1 space; 5) normal appearing tissue segmentation, in which T1 lesion mask is used to segment basal ganglia/thalami, normal appearing grey matter (NAGM) and normal appearing white matter (NAWM); 6) DWI and PWI map generation; 7) co-registration of basal ganglia/thalami, NAGM, NAWM, DWI and PWI maps in previously segmented FLAIR space; 8) data analysis. All these steps are automatic, except for lesion segmentation and classification. We developed a promising method to limit misclassifications and user errors, providing clinical researchers with a practical and reproducible tool to measure DWI and PWI changes in MS.

10. Consumer Confusion: Reduction Strategies in Higher Education

ERIC Educational Resources Information Center

Drummond, Graeme

2004-01-01

This paper highlights the increasingly important topic of consumer confusion. Drawing parallels with experiences in the private sector, the concept of consumer confusion is explored within the higher education sector; what causes the phenomenon, how do consumers react to it and how can it be negated/minimised? The expansion and commercialisation…

11. Core Knowledge Confusions among University Students

ERIC Educational Resources Information Center

Lindeman, Marjaana; Svedholm, Annika M.; Takada, Mikito; Lonnqvist, Jan-Erik; Verkasalo, Markku

2011-01-01

Previous studies have demonstrated that university students hold several paranormal beliefs and that paranormal beliefs can be best explained with core knowledge confusions. The aim of this study was to explore to what extent university students confuse the core ontological attributes of lifeless material objects (e.g. a house, a stone), living…

12. Web life: Confused at a Higher Level

2010-08-01

This two-person blog owes its name to Enrico Fermi, who supposedly informed a visiting lecturer that although he used to be confused about the lecture topic, "having listened to your lecture, I am still confused. But on a higher level".

13. Consumer Confusion: Reduction Strategies in Higher Education

ERIC Educational Resources Information Center

Drummond, Graeme

2004-01-01

This paper highlights the increasingly important topic of consumer confusion. Drawing parallels with experiences in the private sector, the concept of consumer confusion is explored within the higher education sector; what causes the phenomenon, how do consumers react to it and how can it be negated/minimised? The expansion and commercialisation…

14. Evaluation of efficacy of transcatheter arterial chemoembolization combined with computed tomography-guided radiofrequency ablation for hepatocellular carcinoma using magnetic resonance diffusion weighted imaging and computed tomography perfusion imaging: A prospective study.

PubMed

Shao, Guo-Liang; Zheng, Jia-Ping; Guo, Li-Wen; Chen, Yu-Tang; Zeng, Hui; Yao, Zheng

2017-01-01

The purpose of this study is to evaluate the efficacy of transcatheter arterial chemoembolization (TACE) combined with computed tomography-guided radiofrequency ablation (CT-RFA) in the treatment of hepatocellular carcinoma (HCC) using magnetic resonance diffusion weighted imaging (MR-DWI) and CT perfusion imaging (CT-PI). From January 2008 to January 2014, a total of 522 HCC patients receiving TACE combined with CT-RFA were included in this study. All patients underwent TACE followed by CT-RFA, and 1 day before treatment and 1 month after treatment they received MR-DWI and CT-PI. Enzyme-linked immunosorbent assay (ELISA) was performed to detect the concentration of alpha-fetoprotein (AFP). Tumor response was evaluated using the revised RECIST criteria. One-year follow-up was conducted on all patients. Receiver-operating characteristic (ROC) curve was drawn to evaluate the efficacy of TACE combined with CT-RFA for HCC using MR-DWI and CT-PI. Total effective rate (complete remission [CR] + partial remission [PR]) of TACE combined with CT-RFA for HCC was 82.95%. HCC patients of CR + PR had lower hepatic blood flow (HBF), hepatic blood volume (HBV), permeability surface (PS), hepatic arterial perfusion (HAP), and hepatic perfusion index (HPI) levels than those of SD + PD, but HCC patients of CR + PR had higher mean transit time (MTT) level than those of SD + PD. The patients of PR + CR had higher apparent diffusion coefficient (ADC) values than those of SD + PD. The patients of PR + CR showed lower AFP concentration than those of SD + PD. ROC curve analysis indicated that the area under the curve (AUC) of AFP, HBV, PS, HAP, HPI, and ADC was more than 0.7, but the AUC of HBF, MTT, and PVP were less than 0.7. After treatment, the AFP, HBF, HBV, PS, HAP, and HPI in the HCC patients with recurrence were higher than those in the HCC patients without, but MTT and ADC in the HCC patients with recurrence were lower than those in the HCC

15. Evaluation of efficacy of transcatheter arterial chemoembolization combined with computed tomography-guided radiofrequency ablation for hepatocellular carcinoma using magnetic resonance diffusion weighted imaging and computed tomography perfusion imaging

PubMed Central

Shao, Guo-Liang; Zheng, Jia-Ping; Guo, Li-Wen; Chen, Yu-Tang; Zeng, Hui; Yao, Zheng

2017-01-01

Abstract Background: The purpose of this study is to evaluate the efficacy of transcatheter arterial chemoembolization (TACE) combined with computed tomography-guided radiofrequency ablation (CT-RFA) in the treatment of hepatocellular carcinoma (HCC) using magnetic resonance diffusion weighted imaging (MR-DWI) and CT perfusion imaging (CT-PI). Methods: From January 2008 to January 2014, a total of 522 HCC patients receiving TACE combined with CT-RFA were included in this study. All patients underwent TACE followed by CT-RFA, and 1 day before treatment and 1 month after treatment they received MR-DWI and CT-PI. Enzyme-linked immunosorbent assay (ELISA) was performed to detect the concentration of alpha-fetoprotein (AFP). Tumor response was evaluated using the revised RECIST criteria. One-year follow-up was conducted on all patients. Receiver-operating characteristic (ROC) curve was drawn to evaluate the efficacy of TACE combined with CT-RFA for HCC using MR-DWI and CT-PI. Results: Total effective rate (complete remission [CR] + partial remission [PR]) of TACE combined with CT-RFA for HCC was 82.95%. HCC patients of CR + PR had lower hepatic blood flow (HBF), hepatic blood volume (HBV), permeability surface (PS), hepatic arterial perfusion (HAP), and hepatic perfusion index (HPI) levels than those of SD + PD, but HCC patients of CR + PR had higher mean transit time (MTT) level than those of SD + PD. The patients of PR + CR had higher apparent diffusion coefficient (ADC) values than those of SD + PD. The patients of PR + CR showed lower AFP concentration than those of SD + PD. ROC curve analysis indicated that the area under the curve (AUC) of AFP, HBV, PS, HAP, HPI, and ADC was more than 0.7, but the AUC of HBF, MTT, and PVP were less than 0.7. After treatment, the AFP, HBF, HBV, PS, HAP, and HPI in the HCC patients with recurrence were higher than those in the HCC patients without, but MTT and ADC in the HCC patients with

16. [Compromized myocardial perfusion in arrhythmias (author's transl)].

PubMed

Simon, H; Neumann, G; Felix, R; Hedde, H; Schaede, A; Thurn, P; Winkler, C

1977-09-15

In 7 patients with arrhythmias of various origin the myocardial scintigram displayed either a diffuse or circumscript defect of the perfusion. The coronary arteriogram was normal in all patients. The localized defect of the perfusion in 2 patients was in the region of the upper part of the interventricular septum. Both had a left bundle brunch block. A correlation between the perfusion defect and the electrophysiological abnormality seems probable. The perfusion defect in one of the patients is most probably caused by a previous myocarditis followed by fibrous changes. In the other 6 patients the cause for the perfusion defect is not obvious. A history of myocarditis is missing. The presence of "small vessel disease" in those patients has however to be considered. Our results point to the relation between an abnormality of the microcirculation and arrhythmias in younger patients.

17. Perfusion- and pattern-based quantitative CT indexes using contrast-enhanced dual-energy computed tomography in diffuse interstitial lung disease: relationships with physiologic impairment and prediction of prognosis.

PubMed

Moon, Jung Won; Bae, Jang Pyo; Lee, Ho Yun; Kim, Namkug; Chung, Man Pyo; Park, Hye Yun; Chang, Yongjun; Seo, Joon Beom; Lee, Kyung Soo

2016-05-01

To evaluate automated texture-based segmentation of dual-energy CT (DECT) images in diffuse interstitial lung disease (DILD) patients and prognostic stratification by overlapping morphologic and perfusion information of total lung. Suspected DILD patients scheduled for surgical biopsy were prospectively included. Texture patterns included ground-glass opacity (GGO), reticulation and consolidation. Pattern- and perfusion-based CT measurements were assessed to extract quantitative parameters. Accuracy of texture-based segmentation was analysed. Correlations between CT measurements and pulmonary function test or 6-minute walk test (6MWT) were calculated. Parameters of idiopathic pulmonary fibrosis/usual interstitial pneumonia (IPF/UIP) and non-IPF/UIP were compared. Survival analysis was performed. Overall accuracy was 90.47% for whole lung segmentation. Correlations between mean iodine values of total lung, 50-97.5th (%) attenuation and forced vital capacity or 6MWT were significant. Volume of GGO, reticulation and consolidation had significant correlation with DLco or SpO2 on 6MWT. Significant differences were noted between IPF/UIP and non-IPF/UIP in 6MWT distance, mean iodine value of total lung, 25-75th (%) attenuation and entropy. IPF/UIP diagnosis, GGO ratio, DILD extent, 25-75th (%) attenuation and SpO2 on 6MWT showed significant correlations with survival. DECT combined with pattern analysis is useful for analysing DILD and predicting survival by provision of morphology and enhancement. • Dual-energy CT (DECT) produces morphologic and parenchymal enhancement information. • Automated lung segmentation enables analysis of disease extent and severity. • This prospective study showed value of DECT in DILD patients. • Parameters on DECT enable characterization and survival prediction of DILD.

18. The Confusion of Molecular Particles with Substances.

ERIC Educational Resources Information Center

Selley, N. J.

1978-01-01

Objects to the idea of treating molecular particles, such as molecules and atoms, as equal in kind to substances when discussing chemical reactions, thus confusing their different roles in the theory of matter. (GA)

19. Big Data: Big Confusion? Big Challenges?

DTIC Science & Technology

2015-05-01

12th Annual Acquisition Research Symposium 12th Annual Acquisition Research Symposium Big Data : Big Confusion? Big Challenges? Mary Maureen... Data : Big Confusion? Big Challenges? 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK...Acquisition Research Symposium • ~!& UNC CHARlD1TE 90% of the data in the world today was created in the last two years Big Data growth from

20. Time-resolved multi-channel optical system for assessment of brain oxygenation and perfusion by monitoring of diffuse reflectance and fluorescence

Milej, D.; Gerega, A.; Kacprzak, M.; Sawosz, P.; Weigl, W.; Maniewski, R.; Liebert, A.

2014-03-01

Time-resolved near-infrared spectroscopy is an optical technique which can be applied in tissue oxygenation assessment. In the last decade this method is extensively tested as a potential clinical tool for noninvasive human brain function monitoring and imaging. In the present paper we show construction of an instrument which allows for: (i) estimation of changes in brain tissue oxygenation using two-wavelength spectroscopy approach and (ii) brain perfusion assessment with the use of single-wavelength reflectometry or fluorescence measurements combined with ICG-bolus tracking. A signal processing algorithm based on statistical moments of measured distributions of times of flight of photons is implemented. This data analysis method allows for separation of signals originating from extra- and intracerebral tissue compartments. In this paper we present compact and easily reconfigurable system which can be applied in different types of time-resolved experiments: two-wavelength measurements at 687 and 832 nm, single wavelength reflectance measurements at 760 nm (which is at maximum of ICG absorption spectrum) or fluorescence measurements with excitation at 760 nm. Details of the instrument construction and results of its technical tests are shown. Furthermore, results of in-vivo measurements obtained for various modes of operation of the system are presented.

1. Prediction of Stroke Onset Is Improved by Relative Fluid-Attenuated Inversion Recovery and Perfusion Imaging Compared to the Visual Diffusion-Weighted Imaging/Fluid-Attenuated Inversion Recovery Mismatch.

PubMed

Wouters, Anke; Dupont, Patrick; Norrving, Bo; Laage, Rico; Thomalla, Götz; Albers, Gregory W; Thijs, Vincent; Lemmens, Robin

2016-10-01

Acute stroke patients with unknown time of symptom onset are ineligible for thrombolysis. The diffusion-weighted imaging and fluid-attenuated inversion recovery (FLAIR) mismatch is a reasonable predictor of stroke within 4.5 hours of symptom onset, and its clinical usefulness in selecting patients for thrombolysis is currently being investigated. The accuracy of the visual mismatch rating is moderate, and we hypothesized that the predictive value of stroke onset within 4.5 hours could be improved by including various clinical and imaging parameters. In this study, 141 patients in whom magnetic resonance imaging was obtained within 9 hours after symptom onset were included. Relative FLAIR signal intensity was calculated in the region of nonreperfused core. Mean Tmax was calculated in the total region with Tmax >6 s. Mean relative FLAIR, mean Tmax, lesion volume with Tmax >6 s, age, site of arterial stenosis, core volume, and location of infarct were analyzed by logistic regression to predict stroke onset time before or after 4.5 hours. Receiver-operating characteristic curve analysis revealed an area under the curve of 0.68 (95% confidence interval 0.59-0.78) for the visual diffusion-weighted imaging/FLAIR mismatch, thereby correctly classifying 69% of patients with an onset time before or after 4.5 hours. Age, relative FLAIR, and Tmax increased the accuracy significantly (P<0.01) to an area under the curve of 0.82 (95% confidence interval 0.74-0.89). This new predictive model correctly categorized 77% of patients according to stroke onset before versus after 4.5 hours. In patients with unknown stroke onset, the accuracy of predicting time from symptom onset within 4.5 hours is improved by obtaining relative FLAIR and perfusion imaging. © 2016 American Heart Association, Inc.

2. Assessment of functional and structural damage in brain parenchyma in patients with vitamin B12 deficiency: A longitudinal perfusion and diffusion tensor imaging study.

PubMed

Roy, Bhaswati; Trivedi, Richa; Garg, Ravindra K; Gupta, Pradeep K; Tyagi, Ritu; Gupta, Rakesh K

2015-06-01

Vitamin B12 deficiency may cause neural tissue damage. Even in advanced stages, conventional imaging of brain usually appears normal in vitamin B12 deficient patients. The aim of this study was to assess the structural and functional changes in brain of patients with vitamin B12 deficiency before and after six weeks of vitamin B12 supplementation using diffusion tensor imaging and pseudo-continuous arterial spin labelling (PCASL). MR imaging including DTI and PCASL and neuropsychological tests (NPT) were performed in 16 patients with vitamin B12 deficiency and 16 controls before and after 6weeks of therapy. Cerebral blood flow (CBF) derived from PCASL and DTI indices was calculated in brain of patients with vitamin B12 deficiency and controls. Patient with vitamin B12 deficiency showed altered neuropsychological scores and altered CBF as well as fractional anisotropy (FA) values in various brain regions as compared with controls. Both CBF values and neuropsychological scores showed complete reversibility at 6weeks post therapy. Though FA values showed significant recovery, it failed to show complete recovery. Our results suggest that micro-structural recovery lags behind functional recovery in patients with vitamin B12 deficiency following therapy and CBF change may be used as an early predictor of complete recovery in patients with B12 deficiency. Copyright © 2015. Published by Elsevier Inc.

3. Physiological Background of Differences in Quantitative Diffusion-Weighted Magnetic Resonance Imaging Between Acute Malignant and Benign Vertebral Body Fractures: Correlation of Apparent Diffusion Coefficient With Quantitative Perfusion Magnetic Resonance Imaging Using the 2-Compartment Exchange Model.

PubMed

Geith, Tobias; Biffar, Andreas; Schmidt, Gerwin; Sourbron, Steven; Dietrich, Olaf; Reiser, Maximilian; Baur-Melnyk, Andrea

2015-01-01

To test the hypothesis that apparent diffusion coefficient (ADC) in vertebral bone marrow of benign and malignant fractures is related to the volume of the interstitial space, determined with dynamic contrast-enhanced (DCE) magnetic resonance imaging. Patients with acute benign (n = 24) and malignant (n = 19) vertebral body fractures were examined at 1.5 T. A diffusion-weighted single-shot turbo-spin-echo sequence (b = 100 to 600 s/mm) and DCE turbo-FLASH sequence were evaluated. Regions of interest were manually selected for each fracture. Apparent diffusion coefficient was determined with a monoexponential decay model. The DCE magnetic resonance imaging concentration-time curves were analyzed using a 2-compartment tracer-kinetic model. Apparent diffusion coefficient showed a significant positive correlation with interstitial volume in the whole study population (Pearson r = 0.66, P < 0.001), as well as in the malignant (Pearson r = 0.64, P = 0.004) and benign (Pearson r = 0.52, P = 0.01) subgroup. A significant correlation between ADC and the permeability-surface area product could be observed when analyzing the whole study population (Spearman rs = 0.40, P = 0.008), but not when separately examining the subgroups. Plasma flow showed a significant correlation with ADC in benign fractures (Pearson r = 0.23, P = 0.03). Plasma volume did not show significant correlations with ADC. The results support the hypothesis that the ADC of a lesion is inversely correlated to its cellularity. This explains previous observations that ADC is reduced in more malignant lesions.

4. Avogadro Number and Mole: A Royal Confusion.

ERIC Educational Resources Information Center

Emiliani, Cesare

1991-01-01

There is a great deal of confusion in physics and chemistry textbooks, dictionaries, manuals, and handbooks about the definition of Avogadro's number and the term "mole." Avogadro's number is defined simply as the number of atomic mass units in one gram. Mole is defined as the mass of one Avogadro number of identical items. (Author/PR)

5. Confusion between Odds and Probability, a Pandemic?

ERIC Educational Resources Information Center

Fulton, Lawrence V.; Mendez, Francis A.; Bastian, Nathaniel D.; Musal, R. Muzaffer

2012-01-01

This manuscript discusses the common confusion between the terms probability and odds. To emphasize the importance and responsibility of being meticulous in the dissemination of information and knowledge, this manuscript reveals five cases of sources of inaccurate statistical language imbedded in the dissemination of information to the general…

6. NOMENCLATURAL CONFUSION ON ECLIPTA PROSTRATE (L.) L.

PubMed Central

Balu, S.; Rao, G. R.

1991-01-01

Eclipta prostrate (L.) L. (Asterceae) is a valuable plant used in the treatment of various human ailments in Ayurveda and Siddha systems. Nomenclatural confusion prevails as different plants are mentioned in Indian medical literature as Bhringaraja and Karisalahganni. It is evident from the present study that the nomenclature Bhringaraja and Karisalanganni must be restricted only to Eclipta prostrate (L.) L. PMID:22556566

7. Avogadro Number and Mole: A Royal Confusion.

ERIC Educational Resources Information Center

Emiliani, Cesare

1991-01-01

There is a great deal of confusion in physics and chemistry textbooks, dictionaries, manuals, and handbooks about the definition of Avogadro's number and the term "mole." Avogadro's number is defined simply as the number of atomic mass units in one gram. Mole is defined as the mass of one Avogadro number of identical items. (Author/PR)

8. KQED: A Case Study in Confusion.

ERIC Educational Resources Information Center

Huttenstine, Marian L.; Hamner, Claire

The United States Supreme Court's ruling in the "Houchins v KQED" case exemplifies the confusion of that court concerning any consistent view of the First Amendment of the United States Constitution, especially in terms of newsgathering and prior restraint. In this case, the Court reversed a lower court's decision that had held invalid a…

9. Confusion between Odds and Probability, a Pandemic?

ERIC Educational Resources Information Center

Fulton, Lawrence V.; Mendez, Francis A.; Bastian, Nathaniel D.; Musal, R. Muzaffer

2012-01-01

This manuscript discusses the common confusion between the terms probability and odds. To emphasize the importance and responsibility of being meticulous in the dissemination of information and knowledge, this manuscript reveals five cases of sources of inaccurate statistical language imbedded in the dissemination of information to the general…

10. Dichotic Listening and Left-Right Confusion

ERIC Educational Resources Information Center

Hirnstein, Marco

2011-01-01

The present study examined the relationship between individual differences in dichotic listening (DL) and the susceptibility to left-right confusion (LRC). Thirty-six men and 59 women completed a consonant-vowel DL test, a behavioral LRC task, and an LRC self-rating questionnaire. Significant negative correlations between overall DL accuracy and…

11. Dichotic Listening and Left-Right Confusion

ERIC Educational Resources Information Center

Hirnstein, Marco

2011-01-01

The present study examined the relationship between individual differences in dichotic listening (DL) and the susceptibility to left-right confusion (LRC). Thirty-six men and 59 women completed a consonant-vowel DL test, a behavioral LRC task, and an LRC self-rating questionnaire. Significant negative correlations between overall DL accuracy and…

12. Is It Kingdom or Domains? Confusion & Solutions

ERIC Educational Resources Information Center

Blackwell, Will H.

2004-01-01

A confusion regarding the number of kingdoms that should be recognized and the inclusion of domains in the traditional kingdom-based classification found in the higher levels of classification of organisms is presented. Hence, it is important to keep in mind future modifications that may occur in the classification systems and to recognize…

13. When is stacking confusing? The impact of confusion on stacking in deep H I galaxy surveys

Jones, Michael G.; Haynes, Martha P.; Giovanelli, Riccardo; Papastergis, Emmanouil

2016-01-01

We present an analytic model to predict the H I mass contributed by confused sources to a stacked spectrum in a generic H I survey. Based on the ALFALFA (Arecibo Legacy Fast ALFA) correlation function, this model is in agreement with the estimates of confusion present in stacked Parkes telescope data, and was used to predict how confusion will limit stacking in the deepest Square Kilometre Array precursor H I surveys. Stacking with LADUMA (Looking At the Distant Universe with MeerKAT) and DINGO UDEEP (Deep Investigation of Neutral Gas Origins - Ultra Deep) data will only be mildly impacted by confusion if their target synthesized beam size of 10 arcsec can be achieved. Any beam size significantly above this will result in stacks that contain a mass in confused sources that is comparable to (or greater than) that which is detectable via stacking, at all redshifts. CHILES (COSMOS H I Large Extragalactic Survey) 5 arcsec resolution is more than adequate to prevent confusion influencing stacking of its data, throughout its bandpass range. FAST (Five hundred metre Aperture Spherical Telescope) will be the most impeded by confusion, with H I surveys likely becoming heavily confused much beyond z = 0.1. The largest uncertainties in our model are the redshift evolution of the H I density of the Universe and the H I correlation function. However, we argue that the two idealized cases we adopt should bracket the true evolution, and the qualitative conclusions are unchanged regardless of the model choice. The profile shape of the signal due to confusion (in the absence of any detection) was also modelled, revealing that it can take the form of a double Gaussian with a narrow and wide component.

14. Perfusion visualization and analysis for pulmonary embolism

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.

15. Prognosis Prediction of Measurable Enhancing Lesion after Completion of Standard Concomitant Chemoradiotherapy and Adjuvant Temozolomide in Glioblastoma Patients: Application of Dynamic Susceptibility Contrast Perfusion and Diffusion-Weighted Imaging

PubMed Central

Kim, Jae Hyun; Choi, Seung Hong; Ryoo, Inseon; Yun, Tae Jin; Kim, Tae Min; Lee, Se-Hoon; Park, Chul-Kee; Kim, Ji-Hoon; Sohn, Chul-Ho; Park, Sung-Hye; Kim, Il Han

2014-01-01

Purpose To assess the prognosis predictability of a measurable enhancing lesion using histogram parameters produced by the normalized cerebral blood volume (nCBV) and normalized apparent diffusion coefficient (nADC) after completion of standard concomitant chemoradiotherapy (CCRT) and adjuvant temozolomide (TMZ) medication in glioblastoma multiforme (GBM) patients. Materials and Methods This study was approved by the institutional review board (IRB), and the requirement for informed consent was waived. A total of 59 patients with newly diagnosed GBM who received standard CCRT with TMZ and adjuvant TMZ for six cycles underwent perfusion-weighted and diffusion-weighted imaging. Twenty-seven patients had a measurable enhancing lesion and 32 patients lacked a measurable enhancing lesion based on the Response Assessment in Neuro-Oncology (RANO) criteria in the follow-up MRI, which was performed within 3 months after adjuvant TMZ therapy was completed. We measured the nCBV and nADC histogram parameters based on the measurable enhancing lesion. The progression free survival (PFS) was analyzed by the Kaplan-Meier method with the use of the log-rank test. Results The median PFS of patients lacking measurable enhancing lesion was longer than for those with measurable enhancing lesions (17.6 vs 3.3 months, P<.0001). There was a significant, positive correlation between the 99th percentile nCBV value of a measurable enhancing lesion and the PFS (P = .044, R2 = .152). In addition, the median PFS was longer in patients with a 99th percentile nCBV value ≧4.5 than it was in those with a value <4.5 (4.4 vs 3.1 months, P = .036). Conclusion We found that the nCBV value can be used for the prognosis prediction of a measurable enhancing lesion after the completion of standard treatment for GBM, wherein a high 99th percentile nCBV value (≧4.5) suggests a better PFS for GBM patients. PMID:25419975

16. Applying the concept of consumer confusion to healthcare: development and validation of a patient confusion model.

PubMed

Gebele, Christoph; Tscheulin, Dieter K; Lindenmeier, Jörg; Drevs, Florian; Seemann, Ann-Kathrin

2014-01-01

As patient autonomy and consumer sovereignty increase, information provision is considered essential to decrease information asymmetries between healthcare service providers and patients. However, greater availability of third party information sources can have negative side effects. Patients can be confused by the nature, as well as the amount, of quality information when making choices among competing health care providers. Therefore, the present study explores how information may cause patient confusion and affect the behavioral intention to choose a health care provider. Based on a quota sample of German citizens (n = 198), the present study validates a model of patient confusion in the context of hospital choice. The study results reveal that perceived information overload, perceived similarity, and perceived ambiguity of health information impact the affective and cognitive components of patient confusion. Confused patients have a stronger inclination to hastily narrow down their set of possible decision alternatives. Finally, an empirical analysis reveals that the affective and cognitive components of patient confusion mediate perceived information overload, perceived similarity, and perceived ambiguity of information. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

17. [Confusion and solution for vital pulp therapy].

PubMed

Dingming, Huang; Qian, Lu; Qian, Liao; Ling, Ye; Xuedong, Zhou

2017-06-01

Dental pulp tissue plays a role in forming dentin, providing nutrition, conducting pain, and generating protective responses to environmental stimuli. Bacterial infection is the main cause of pulp disease, where histopathological changes are the histological basis for determining the choice of treatment and the evaluation of therapeutic effect. Thus, particular attention should be given to eliminate infection, as well as preserve and maintain pulpal health in teeth that show reversible or limited pulpal injuries. Vital pulp therapy, especially its indications and prognostic factors, has been a research hotspot that often causes confusion among clinicians. In this paper, we briefly introduce the confusion and solution for vital pulp therapy in terms of indications, pulp condition assessment, infection elimination, and capping material selection. In addition, we develop a clinical pathway and an operation normalization of vital pulp therapy to better perform the therapy.

18. Persistent Confusion and Controversy Surrounding Gene Patents

PubMed Central

Guerrini, Christi J.; Majumder, Mary A.; McGuire, Amy L.

2016-01-01

There is persistent confusion and controversy surrounding basic issues of patent law relevant to the genomics industry. Uncertainty and conflict can lead to the adoption of inefficient practices and exposure to liability. The development of patent-specific educational resources for industry members, as well as the prompt resolution of patentability rules unsettled by recent U.S. Supreme Court decisions, are therefore urgently needed. PMID:26849516

19. A compact instrument to measure perfusion of vasculature in transplanted maxillofacial free flaps

Kolodziejski, Noah J.; Stapels, Christopher J.; McAdams, Daniel R.; Fernandez, Daniel E.; Podolsky, Matthew J.; Farkas, Dana; Ward, Brent B.; Vartarian, Mark; Feinberg, Stephen E.; Lee, Seung Yup; Parikh, Urmi; Mycek, Mary-Ann; Christian, James F.

2016-03-01

The vascularization and resulting perfusion of transferred tissues are critical to the success of grafts in buried free flap transplantations. To enable long-term clinical monitoring of grafted tissue perfusion during neovascularization and endothelialization, we are developing an implantable instrument for the continuous monitoring of perfusion using diffuse correlation spectroscopy (DCS), and augmented with diffuse reflectance spectroscopy (DRS). This work discusses instrument construction, integration, and preliminary results using a porcine graft model.

20. Analyzing Mode Confusion via Model Checking

NASA Technical Reports Server (NTRS)

Luettgen, Gerald; Carreno, Victor

1999-01-01

Mode confusion is one of the most serious problems in aviation safety. Today's complex digital flight decks make it difficult for pilots to maintain awareness of the actual states, or modes, of the flight deck automation. NASA Langley leads an initiative to explore how formal techniques can be used to discover possible sources of mode confusion. As part of this initiative, a flight guidance system was previously specified as a finite Mealy automaton, and the theorem prover PVS was used to reason about it. The objective of the present paper is to investigate whether state-exploration techniques, especially model checking, are better able to achieve this task than theorem proving and also to compare several verification tools for the specific application. The flight guidance system is modeled and analyzed in Murphi, SMV, and Spin. The tools are compared regarding their system description language, their practicality for analyzing mode confusion, and their capabilities for error tracing and for animating diagnostic information. It turns out that their strengths are complementary.

1. Medial perirhinal cortex disambiguates confusable objects.

PubMed

Kivisaari, Sasa L; Tyler, Lorraine K; Monsch, Andreas U; Taylor, Kirsten I

2012-12-01

Our brain disambiguates the objects in our cluttered visual world seemingly effortlessly, enabling us to understand their significance and to act appropriately. The role of anteromedial temporal structures in this process, particularly the perirhinal cortex, is highly controversial. In some accounts, the perirhinal cortex is necessary for differentiating between perceptually and semantically confusable objects. Other models claim that the perirhinal cortex neither disambiguates perceptually confusable objects nor plays a unique role in semantic processing. One major hurdle to resolving this central debate is the fact that brain damage in human patients typically encompasses large portions of the anteromedial temporal lobe, such that the identification of individual substructures and precise neuroanatomical locus of the functional impairments has been difficult. We tested these competing accounts in patients with Alzheimer's disease with varying degrees of atrophy in anteromedial structures, including the perirhinal cortex. To assess the functional contribution of each anteromedial temporal region separately, we used a detailed region of interest approach. From each participant, we obtained magnetic resonance imaging scans and behavioural data from a picture naming task that contrasted naming performance with living and non-living things as a way of manipulating perceptual and semantic confusability; living things are more similar to one another than non-living things, which have more distinctive features. We manually traced neuroanatomical regions of interest on native-space cortical surface reconstructions to obtain mean thickness estimates for the lateral and medial perirhinal cortex and entorhinal cortex. Mean cortical thickness in each region of interest, and hippocampal volume, were submitted to regression analyses predicting naming performance. Importantly, atrophy of the medial perirhinal cortex, but not lateral perirhinal cortex, entorhinal cortex or

2. Confusion and Complex Learning during Interactions with Computer Learning Environments

ERIC Educational Resources Information Center

Lehman, Blair; D'Mello, Sidney; Graesser, Art

2012-01-01

Folk wisdom holds that being confused is detrimental to learning. However, research on emotions and learning suggest a somewhat more complex relationship between confusion and learning outcomes. In fact, it has been proposed that impasses that trigger states of cognitive disequilibrium and confusion can create opportunities for deep learning of…

3. Too Many Choices Confuse Patients With Dementia

PubMed Central

Hamdy, R. C.; Lewis, J. V.; Kinser, A.; Depelteau, A.; Copeland, R.; Kendall-Wilson, T.; Whalen, K.

2017-01-01

Choices are often difficult to make by patients with Alzheimer Dementia. They often become acutely confused when faced with too many options because they are not able to retain in their working memory enough information about the various individual choices available. In this case study, we describe how an essentially simple benign task (choosing a dress to wear) can rapidly escalate and result in a catastrophic outcome. We examine what went wrong in the patient/caregiver interaction and how that potentially catastrophic situation could have been avoided or defused. PMID:28904992

4. Diffusion-weighted imaging or computerized tomography perfusion assessment with clinical mismatch in the triage of wake up and late presenting strokes undergoing neurointervention with Trevo (DAWN) trial methods.

PubMed

Jovin, Tudor G; Saver, Jeffrey L; Ribo, Marc; Pereira, Vitor; Furlan, Anthony; Bonafe, Alain; Baxter, Blaise; Gupta, Rishi; Lopes, Demetrius; Jansen, Olav; Smith, Wade; Gress, Daryl; Hetts, Steven; Lewis, Roger J; Shields, Ryan; Berry, Scott M; Graves, Todd L; Malisch, Tim; Rai, Ansaar; Sheth, Kevin N; Liebeskind, David S; Nogueira, Raul G

2017-08-01

Rationale Efficacy of mechanical thrombectomy for acute stroke due to large vessel occlusion initiated beyond 6 h of time last seen well has not been demonstrated in randomized trials. Aim To establish whether subjects considered to have substantial areas of salvageable brain based on age-adjusted clinical core mismatch who can undergo endovascular treatment within 6-24 h from time last seen well (TLSW) have better outcomes at three months compared to subjects treated with standard medical therapy alone. Age-adjusted clinical core mismatch is defined by age (≤80 or >80 years), baseline National Institutes of Health Stroke Scale (NIHSS) (10-20 or ≥21), and core size (0-20 cm(3) in subjects older than 80 and, in subjects younger than 80, 0-30 cm(3) with NIHSS 10-20 and 31-50 cm(3) with NIHSS ≥21). Design Prospective, randomized, multicenter, Bayesian adaptive-enrichment, open label trial with blinded endpoint assessment. For the purpose of enrolment, ischemic core size will be evaluated by CT perfusion or magnetic resonance imaging-diffusion-weighted imaging measured by automated software (RAPID). Procedures Subjects with acute ischemic stroke due to computed tomography angiography- or magnetic resonance angiogram-proven arterial occlusion of the intracranial internal carotid and/or proximal middle cerebral artery (M1) with age-adjusted clinical core mismatch in whom treatment can be initiated between 6 and 24 h from TSLW are randomized in a 1:1 ratio to receive mechanical embolectomy with the Trevo device or medical management alone. Sequential interim analyses allowing adaptation of enrolment criteria or stopping new enrolment for futility or predicted success will occur in every 50 randomized patients starting at 150 to a maximum of 500 patients. Study outcomes The primary endpoint is the modified Rankin Scale score at 90 days. The primary safety outcome is stroke-related mortality at 90 days. Analysis The primary endpoint, expressed as a utility

5. Making Sense of Confusion: Relating Performance, Confidence, and Self-Efficacy to Expressions of Confusion in an Introductory Physics Class

ERIC Educational Resources Information Center

Dowd, Jason E.; Araujo, Ives; Mazur, Eric

2015-01-01

Although confusion is generally perceived to be negative, educators dating as far back as Socrates, who asked students to question assumptions and wrestle with ideas, have challenged this notion. Can confusion be productive? How should instructors interpret student expressions of confusion? During two semesters of introductory physics that…

6. Making Sense of Confusion: Relating Performance, Confidence, and Self-Efficacy to Expressions of Confusion in an Introductory Physics Class

ERIC Educational Resources Information Center

Dowd, Jason E.; Araujo, Ives; Mazur, Eric

2015-01-01

Although confusion is generally perceived to be negative, educators dating as far back as Socrates, who asked students to question assumptions and wrestle with ideas, have challenged this notion. Can confusion be productive? How should instructors interpret student expressions of confusion? During two semesters of introductory physics that…

PubMed

Stasa, Helen; Cashin, Andrew; Buckley, Thomas; Donoghue, Judith

2014-03-01

8. The confusion technique untangled: its theoretical rationale and preliminary classification.

PubMed

Otani, A

1989-01-01

This article examines the historical development of Milton H. Erickson's theoretical approach to hypnosis using confusion. Review of the literature suggests that the Confusion Technique, in principle, consists of a two-stage "confusion-restructuring" process. The article also attempts to categorize several examples of confusion suggestions by seven linguistic characteristics: (1) antonyms, (2) homonyms, (3) synonyms, (4) elaboration, (5) interruption, (6) echoing, and (7) uncommon words. The Confusion Technique is an important yet little studied strategy developed by Erickson. More work is urged to investigate its nature and properties.

9. Abdominal perfusion computed tomography.

PubMed

Ogul, Hayri; Bayraktutan, Ummugulsum; Kizrak, Yesim; Pirimoglu, Berhan; Yuceler, Zeynep; Sagsoz, M Erdem; Yilmaz, Omer; Aydinli, Bulent; Ozturk, Gurkan; Kantarci, Mecit

2013-02-01

The purpose of this article is to provide an up to date review on the spectrum of applications of perfusion computed tomography (CT) in the abdomen. New imaging techniques have been developed with the objective of obtaining a structural and functional analysis of different organs. Recently, perfusion CT has aroused the interest of many researchers who are studying the applicability of imaging modalities in the evaluation of abdominal organs and diseases. Per-fusion CT enables fast, non-invasive imaging of the tumor vascular physiology. Moreover, it can act as an in vivo biomarker of tumor-related angiogenesis.

10. Abdominal Perfusion Computed Tomography

PubMed Central

Ogul, Hayri; Bayraktutan, Ummugulsum; Kizrak, Yesim; Pirimoglu, Berhan; Yuceler, Zeynep; Sagsoz, M. Erdem; Yilmaz, Omer; Aydinli, Bulent; Ozturk, Gurkan; Kantarci, Mecit

2013-01-01

The purpose of this article is to provide an up to date review on the spectrum of applications of perfusion computed tomography (CT) in the abdomen. New imaging techniques have been developed with the objective of obtaining a structural and functional analysis of different organs. Recently, perfusion CT has aroused the interest of many researchers who are studying the applicability of imaging modalities in the evaluation of abdominal organs and diseases. Per-fusion CT enables fast, non-invasive imaging of the tumor vascular physiology. Moreover, it can act as an in vivo biomarker of tumor-related angiogenesis. PMID:25610249

11. Dutch perfusion incident survey.

PubMed

Groenenberg, Ingrid; Weerwind, Patrick W; Everts, Peter A M; Maessen, Jos G

2010-09-01

Cardiopulmonary bypass procedures remain complex, involving many potential risks. Therefore, a nationwide retrospective study was conducted to gain insight into the number of incidents and accidents in Dutch adult perfusion practice. An anonymous postal survey (85 questions about hardware, disposables, fluids and medication, air emboli, anticoagulation, practice, and safety measures) was sent to all Dutch perfusionists involved in adult cardiovascular perfusion during 2006 and 2007. To guarantee complete anonymity, respondents were asked to return the survey to a notary who discarded personal information. The net response rate was 72% and covered 23,500 perfusions. Individual respondents performed 240 ± 103 perfusions during the 2-year study period and had 13.8 ± 8.7 years of practical experience. The incident rate was 1 per 15.6 perfusions and the adverse event rate was 1 per 1,236 perfusions. The three most reported incidents were: (1) persistent inability to raise the activated coagulation time above 400s during perfusion (184 incidents); (2) an allergic or anaphylactic reaction to drugs, fluids, or blood products (114 incidents); and (3) clotting formation in the extracorporeal circuit (74 incidents). Furthermore, pre-bypass safety measures showed no statistically significant association with the reported incidents. In comparison with data from the recent literature, the reported number of incidents is high. Nevertheless, the adverse outcome rate is well matched to other published surveys. The relatively high response rate conveys the impression that the Dutch perfusionist is vigilant and willing to report incidents. Hence, a web-based Dutch perfusion incident registration system is recommended.

12. Defensive medicine: No wonder policymakers are confused.

PubMed

Kapp, Marshall B

2016-01-01

Discussions regarding defensive medical practice often result in proposals for public policy actions. Such proposals generally are premised on assumptions about defensive medicine, namely, that it (a) is driven by physicians' legal anxieties, (b) constitutes bad medical practice, (c) drives up health care costs, (d) varies depending on a jurisdiction's particular tort law climate, (e) depends on medical specialty and a physician's own prior experience as a malpractice defendant, and (f) is a rational response to actual legal risks confronting physicians. This article examines a sample of recent literature focusing on defensive medicine and finds that the messages conveyed vary widely, helping to explain the confusion experienced by many policymakers trying to improve the quality and affordability of health care.

13. EBM, HTA, and CER: clearing the confusion.

PubMed

Luce, Bryan R; Drummond, Michael; Jönsson, Bengt; Neumann, Peter J; Schwartz, J Sanford; Siebert, Uwe; Sullivan, Sean D

2010-06-01

The terms evidence-based medicine (EBM), health technology assessment (HTA), comparative effectiveness research (CER), and other related terms lack clarity and so could lead to miscommunication, confusion, and poor decision making. The objective of this article is to clarify their definitions and the relationships among key terms and concepts. This article used the relevant methods and policy literature as well as the websites of organizations engaged in evidence-based activities to develop a framework to explain the relationships among the terms EBM, HTA, and CER. This article proposes an organizing framework and presents a graphic demonstrating the differences and relationships among these terms and concepts. More specific terminology and concepts are necessary for an informed and clear public policy debate. They are even more important to inform decision making at all levels and to engender more accountability by the organizations and individuals responsible for these decisions.

14. Science and ministry: confusion and reality.

PubMed

Handzo, George F

2002-01-01

The professional pastoral care community generates a great deal of heat but precious little light during its debate about the use of scientific process in the practice of ministry. This result is due in large part to confusion about the basic tasks and processes of science and its role in both organized religion and the current health care environment. Clergy have often not understood that science and faith are different enterprises, that science and art are overlapping processes, and that both science and ministry are means and not ends in themselves. In the current health care environment, the ability to use scientific processes and speak its language are not only essential to the survival of professional pastoral care but are necessary to promote the goals of pastoral care and enhance our ministry.

15. Econometric models for predicting confusion crop ratios

NASA Technical Reports Server (NTRS)

Umberger, D. E.; Proctor, M. H.; Clark, J. E.; Eisgruber, L. M.; Braschler, C. B. (Principal Investigator)

1979-01-01

Results for both the United States and Canada show that econometric models can provide estimates of confusion crop ratios that are more accurate than historical ratios. Whether these models can support the LACIE 90/90 accuracy criterion is uncertain. In the United States, experimenting with additional model formulations could provide improved methods models in some CRD's, particularly in winter wheat. Improved models may also be possible for the Canadian CD's. The more aggressive province/state models outperformed individual CD/CRD models. This result was expected partly because acreage statistics are based on sampling procedures, and the sampling precision declines from the province/state to the CD/CRD level. Declining sampling precision and the need to substitute province/state data for the CD/CRD data introduced measurement error into the CD/CRD models.

16. Star Confusion Effect on SIM PlanetQuest Astrometric Performance

NASA Technical Reports Server (NTRS)

Zhai, C.; Yu, M.; Milman, M.; Fathpour, N.; Morales, M.; Nemati, B.; Regehr, M.; Heflin, M.; Sievers, L.

2007-01-01

SIM PlanetQuest will measure star positions to an accuracy of a few microarcseconds using precise white light fringe measurements. One challenge for SIM observation scenario is "star confusion," where multiple stars are present in the instrument field of view. This is especially relevant for observing dim science targets because the density of number of stars increases rapidly with star magnitude. We study the effect of star confusion on the SIM astrometric performance due to systematic fringe errors caused by the extra photons from the confusion star(s}. Since star confusion from multiple stars may be analyzed as a linear superposition of the effect from single star confusion, we quantify the astrometric errors due to single star confusion surveying over many spectral types, including AOV, FOV, K5III, and MOV, and for various visual magnitude differences. To the leading order, the star confusion effect is characterized by the magnitude difference, spectral difference, and the angular separation between the target and confusion stars.Strategies for dealing with star confusion are presented. For example, since the presence of additional sources in the field of view leads to inconsistent delay estimates from different channels, with sufficient signal to noise ratio, the star confusion can be detected using chi-square statistics of fringe measurements from multiple spectral channels. An interesting result is that the star confusion can be detected even though the interferometer cannot resolve the separation between the target and confusion stars when their spectra are sufficiently different. Other strategies for mitigating the star confusion effect are also discussed.

17. Making sense of confusion: Relating performance, confidence, and self-efficacy to expressions of confusion in an introductory physics class

Dowd, Jason E.; Araujo, Ives; Mazur, Eric

2015-06-01

Although confusion is generally perceived to be negative, educators dating as far back as Socrates, who asked students to question assumptions and wrestle with ideas, have challenged this notion. Can confusion be productive? How should instructors interpret student expressions of confusion? During two semesters of introductory physics that involved Just-in-Time Teaching (JiTT) and research-based reading materials, we evaluated performance on reading assignments while simultaneously measuring students' self-assessment of their confusion over the preclass reading material (N =137 ; Nfall=106 , Nspring=88 ). We examined the relationship between confusion and correctness, confidence in reasoning, and (in the spring) precourse self-efficacy. We find that student expressions of confusion before coming to class are negatively related to correctness on preclass content-related questions, confidence in reasoning on those questions, and self-efficacy, but weakly positively related to final grade when controlling for these factors (β =0.23 , p =0.03 ).

18. [Acute confusion in the geriatric patient].

PubMed

Zanocchi, M; Vallero, F; Norelli, L; Zaccagna, B; Spada, S; Fabris, F

1998-05-01

During 1996, 585 patients, aged 55 to 96, were admitted into hospital at the Geriatric Department of Ospedale Maggiore (Turin). Acute confusion was seen in 22.2% of these patients who tended to have more serious clinical condition, were more likely to have chronic cognitive impairment, were treated with a greater number of drugs and suffered more from immobility with pressure ulcer. The confusional state, manifested at admission to Geriatric department, was mostly related with the patient's clinical severity, while the one which developed during hospital stay was linked to situations of physical frailty, as pressure ulcer and low albumin values. The most frequent causes of acute confusional state were acute infectious diseases, heart failure, gastro-intestinal bleeding with secondary anaemia, stroke and dehydration. In many cases the very cause of the acute confusional state could not be identified. Falls, more than 31 days length of stay in hospital and death were more frequent in patients suffering from confusional state. Chronic cognitive impairment, functional dependence, clinical severity and treatment involving a great number of drugs, are the main contributing factors in this syndrome. Thus, a multi-dimensional evaluation which takes into account both clinical-functional and socio-economical aspects, is useful for a correct preventive and diagnostic approach of acute confusional state.

19. Intraosseous haemangioma: semantic and medical confusion.

PubMed

Kadlub, N; Dainese, L; Coulomb-L'Hermine, A; Galmiche, L; Soupre, V; Lepointe, H Ducou; Vazquez, M-P; Picard, A

2015-06-01

The literature is rich in case reports of intraosseous haemangioma, although most of these are actually cases of venous or capillary malformations. To illustrate this confusion in terminology, we present three cases of slow-flow vascular malformations misnamed as intraosseous haemangioma. A retrospective study of children diagnosed with intraosseous haemangioma was conducted. Clinical and radiological data were evaluated. Histopathological examinations and immunohistochemical studies were redone by three independent pathologists to classify the lesions according to the International Society for the Study of Vascular Anomalies (ISSVA) and World Health Organization (WHO) classifications. Three children who had presented with jaw haemangiomas were identified. Computed tomography scan patterns were not specific. All tumours were GLUT-1-negative and D2-40-negative. The lesions were classified as central haemangiomas according to the WHO, and as slow-flow malformations according to the ISSVA. The classification of vascular anomalies is based on clinical, radiological, and histological differences between vascular tumours and malformations. Based on this classification, the evolution of the lesion can be predicted and adequate treatment applied. The binary ISSVA classification is widely accepted and should be applied for all vascular lesions.

20. 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.

1. The diffusion of ions in unconsolidated sediments

USGS Publications Warehouse

Manheim, F. T.

1970-01-01

Diffusion in unconsolidated sediments generally proceeds at rates ranging from half to one twentieth of those applying to diffusion of ions and molecules in free solution. Diffusion rates are predictable with respect to porosity and path tortuosity in host sediments, and can be conveniently measured by determinations of electrical resistivity on bulk sediment samples. Net ion flux is further influenced by reactions of diffusing species with enclosing sediments, but such influences should not be confused with or lumped with diffusion processes. ?? 1970.

2. [Portable peristaltic perfusion pumps].

PubMed

Magallón Pedrera, I; Soto Torres, I

1999-11-01

Portable peristaltic perfusion pumps allow one to administer pharmaceuticals in hospitals as well as in primary health care centers and furthermore these pumps present multiple advantages for patients and their families since they make it possible to carry out treatment in a patient's home while at the same time lowering the costs involved. The authors analyze the most out standing aspects of portable peristaltic perfusion pumps along with their characteristics, installation, programming, and how to turn them on; in addition, the authors list the maintenance care which these pumps require.

3. Stroke mimic: Perfusion magnetic resonance imaging of a patient with ictal paralysis.

PubMed

Sanghvi, D; Goyal, C; Mani, J

2016-01-01

We present an uncommon case of clinically diagnosed window period stroke subsequently recognised on diffusion - perfusion MRI as ictal paralysis due to focal inhibitory seizures or negative motor seizures. This case highlights the importance of MRI with perfusion imaging in establishing the diagnosis of stroke mimics and avoiding unnecessary thrombolysis.

4. Stroke mimic: Perfusion magnetic resonance imaging of a patient with ictal paralysis

PubMed Central

Sanghvi, D; Goyal, C; Mani, J

2016-01-01

We present an uncommon case of clinically diagnosed window period stroke subsequently recognised on diffusionperfusion MRI as ictal paralysis due to focal inhibitory seizures or negative motor seizures. This case highlights the importance of MRI with perfusion imaging in establishing the diagnosis of stroke mimics and avoiding unnecessary thrombolysis. PMID:27763486

5. Dyscalculia, Dysgraphia, and Left-Right Confusion from a Left Posterior Peri-Insular Infarct

PubMed Central

Bhattacharyya, S.; Cai, X.; Klein, J. P.

2014-01-01

The Gerstmann syndrome of dyscalculia, dysgraphia, left-right confusion, and finger agnosia is generally attributed to lesions near the angular gyrus of the dominant hemisphere. A 68-year-old right-handed woman presented with sudden difficulty completing a Sudoku grid and was found to have dyscalculia, dysgraphia, and left-right confusion. Magnetic resonance imaging (MRI) showed a focus of abnormal reduced diffusivity in the left posterior insula and temporoparietal operculum consistent with acute infarct. Gerstmann syndrome from an insular or peri-insular lesion has not been described in the literature previously. Pathological and functional imaging studies show connections between left posterior insular region and inferior parietal lobe. We postulate that the insula and operculum lesion disrupted key functional networks resulting in a pseudoparietal presentation. PMID:24817791

6. Dyscalculia, dysgraphia, and left-right confusion from a left posterior peri-insular infarct.

PubMed

Bhattacharyya, S; Cai, X; Klein, J P

2014-01-01

The Gerstmann syndrome of dyscalculia, dysgraphia, left-right confusion, and finger agnosia is generally attributed to lesions near the angular gyrus of the dominant hemisphere. A 68-year-old right-handed woman presented with sudden difficulty completing a Sudoku grid and was found to have dyscalculia, dysgraphia, and left-right confusion. Magnetic resonance imaging (MRI) showed a focus of abnormal reduced diffusivity in the left posterior insula and temporoparietal operculum consistent with acute infarct. Gerstmann syndrome from an insular or peri-insular lesion has not been described in the literature previously. Pathological and functional imaging studies show connections between left posterior insular region and inferior parietal lobe. We postulate that the insula and operculum lesion disrupted key functional networks resulting in a pseudoparietal presentation.

7. RTI: Court and Case Law--Confusion by Design

ERIC Educational Resources Information Center

Daves, David P.; Walker, David W.

2012-01-01

Professional confusion, as well as case law confusion, exists concerning the fidelity and integrity of response to intervention (RTI) as a defensible procedure for identifying children as having a specific learning disability (SLD) under the Individuals with Disabilities Education Act (IDEA). Division is generated because of conflicting mandates…

8. Clinical Terminology: Anxiety and Confusion amongst Families Undergoing Genetic Counseling.

ERIC Educational Resources Information Center

Chapple, Alison; Campion, Peter; May, Carl

1997-01-01

An ethnographic study of families (N=30) receiving genetic counseling explored participants' perceptions of the process. Focuses on respondents' confusion about the meaning of medical terms. Although clients approved of the way information was presented, terminology was often confusing or frightening. Specific examples are presented and discussed.…

9. Clustering, Seriation, and Subset Extraction of Confusion Data

ERIC Educational Resources Information Center

Brusco, Michael J.; Steinley, Douglas

2006-01-01

The study of confusion data is a well established practice in psychology. Although many types of analytical approaches for confusion data are available, among the most common methods are the extraction of 1 or more subsets of stimuli, the partitioning of the complete stimulus set into distinct groups, and the ordering of the stimulus set. Although…

10. Clustering, Seriation, and Subset Extraction of Confusion Data

ERIC Educational Resources Information Center

Brusco, Michael J.; Steinley, Douglas

2006-01-01

The study of confusion data is a well established practice in psychology. Although many types of analytical approaches for confusion data are available, among the most common methods are the extraction of 1 or more subsets of stimuli, the partitioning of the complete stimulus set into distinct groups, and the ordering of the stimulus set. Although…

11. "Apparent Weight": A Concept that Is Confusing and Unnecessary

ERIC Educational Resources Information Center

Bartlett, Albert A.

2010-01-01

Two recent articles make prominent use of the concept of "apparent weight." The concept of "apparent weight" leads to two confusing inconsistencies. We need to know that with very little change in our representations, we can give our students an improved understanding of "weight" without ever having to invent the appealing but confusing concept of…

12. [Acute confusion syndrome in the hospitalized elderly].

PubMed

Regazzoni, C J; Aduriz, M; Recondo, M

2000-01-01

Our purpose was to determine the in-hospital incidence of delirium among elderly patients, its relation to previous cognitive impairment and the time between admission and its development. We performed an observational study of follow-up in the internal medicine area of a university hospital. We included consecutively and prospectively every patient 70 years or older upon admission. Patients with delirium on admission were excluded, as also were those taking antipsychotic drugs, with severe language or audition impairment, or coming from other sites of internation. We subsequently eliminated patients whose follow-up had not ended by the time the study was concluded, and patients in whom psychosis was diagnosed. Clinical and laboratory data were collected, and patients were prospectively followed until discharge from the hospital, using the Confusion-Assessment-Method (CAM) for the diagnosis of delirium. We analyzed 61 patients of whom 13 developed delirium while hospitalized (in-hospital incidence: 21.31%--CI 95%: 11.03-31.59%). Patients with delirium had had lower scores on Mini Mental State upon admission (median 17 vs 22; p 0.001). During the first 4 days of hospitalization 58.3% of delirium cases occurred not modifying the duration of hospitalization (average: 10.22 days vs 14.38; p = NS). We conclude that the incidence of delirium is high among hospitalized elderly patients specially during the first days, and in those with previous cognitive impairment. We suggest that delirium could be an associated disorder in severe diseases among patients with previous cognitive damage.

13. Sun protection factors: world wide confusion.

PubMed

Osterwalder, U; Herzog, B

2009-11-01

The Sun Protection Factor (SPF) is a very popular instrument in the marketing of sunscreens. Unfortunately it is often not understood how sunscreens work and where the limitations of the SPF are. A lot of aspects of the SPF are confusing, e.g. the race for higher and higher numbers, the effect on SPF when less sunscreen is applied and if sunscreen should be used at all because they may block the Vitamin D synthesis. All this has a negative impact on compliance by the consumer or patient which is the most important influence factor in sun protection. This paper explains how sunscreens work, how the SPF is determined and where the limitations of the current methods exist. The dynamic view of 'UV radiation applied' and the 'UV dose transmitted' through the sunscreen onto the skin as well as onto a substrate in vitro help in the understanding and are also promising approaches in the in vitro assessment. A variation of the in vitro assessment of a sunscreen is the in silico calculation based on the absorption spectrum of the UV filters and an assumption about the irregular sunscreen film on the skin. The sunscreen simulator program can be used to determine how the SPF is affected by applying smaller amounts of sunscreen. Besides the SPF, UVA protection is also discussed. The degree of UVA protection determines the quality of the overall UV protection, whereas the SPF is an indication of the quantity of protection. Furthermore other protection factors such as IPF, iSPF, RSF and p53, and the inhibition of the Vitamin D3 synthesis by sunscreens are also discussed. In conclusion it is shown that the accuracy and robustness of the SPF and other Protection Factors will improve significantly with the availability of true broad-spectrum sunscreens rather than conventional UVB-biased sunscreens, because uniform protection profiles lead to protection independent of the action spectrum of the endpoint and the UV-radiation source.

14. Distribution of perfusion.

PubMed

Glenny, Robb; Robertson, H Thomas

2011-01-01

Local driving pressures and resistances within the pulmonary vascular tree determine the distribution of perfusion in the lung. Unlike other organs, these local determinants are significantly influenced by regional hydrostatic and alveolar pressures. Those effects on blood flow distribution are further magnified by the large vertical height of the human lung and the relatively low intravascular pressures in the pulmonary circulation. While the distribution of perfusion is largely due to passive determinants such as vascular geometry and hydrostatic pressures, active mechanisms such as vasoconstriction induced by local hypoxia can also redistribute blood flow. This chapter reviews the determinants of regional lung perfusion with a focus on vascular tree geometry, vertical gradients induced by gravity, the interactions between vascular and surrounding alveolar pressures, and hypoxic pulmonary vasoconstriction. While each of these determinants of perfusion distribution can be examined in isolation, the distribution of blood flow is dynamically determined and each component interacts with the others so that a change in one region of the lung influences the distribution of blood flow in other lung regions. © 2011 American Physiological Society.

15. A disposable flexible skin patch for clinical optical perfusion monitoring at multiple depths

Farkas, Dana L.; Kolodziejski, Noah J.; Stapels, Christopher J.; McAdams, Daniel R.; Fernandez, Daniel E.; Podolsky, Matthew J.; Christian, James F.; Ward, Brent B.; Vartarian, Mark; Feinberg, Stephen E.; Lee, Seung Yup; Parikh, Urmi; Mycek, Mary-Ann; Joyner, Michael J.; Johnson, Christopher P.; Paradis, Norman A.

2016-03-01

Stable, relative localization of source and detection fibers is necessary for clinical implementation of quantitative optical perfusion monitoring methods such as diffuse correlation spectroscopy (DCS) and diffuse reflectance spectroscopy (DRS). A flexible and compact device design is presented as a platform for simultaneous monitoring of perfusion at a range of depths, enabled by precise location of optical fibers in a robust and secure adhesive patch. We will discuss preliminary data collected on human subjects in a lower body negative pressure model for hypovolemic shock. These data indicate that this method facilitates simple and stable simultaneous monitoring of perfusion at multiple depths and within multiple physiological compartments.

16. Perfusion-weighted MR imaging in persistent hemiplegic migraine.

PubMed

Mourand, Isabelle; Menjot de Champfleur, Nicolas; Carra-Dallière, Clarisse; Le Bars, Emmanuelle; Roubertie, Agathe; Bonafé, Alain; Thouvenot, Eric

2012-03-01

Hemiplegic migraine is a rare type of migraine that has an aura characterized by the presence of motor weakness, which may occasionally last up to several days, and then resolve without sequela. Pathogenesis of migraine remains unclear and, recently, perfusion-weighted imaging (PWI) has provided a non-invasive method to study hemodynamic changes during acute attacks. Two female patients were admitted in our hospital suffering from prolonged hemiparesis. In both cases, they underwent MRI examination using a 1.5 T magnet including axial diffusion-weighted and perfusion sequences. From each perfusion MRI acquisition two regions of interest were delineated on each hemisphere and, the index of flow, cerebral blood volume, mean transit time, and time to peak were recorded and asymmetry indices from each perfusion parameter were calculated. Perfusion alterations were detected during the attacks. In one case, we observed, after 3 h of left hemiparesia, hypoperfusion of the right hemisphere. In the other case, who presented a familial hemiplegic migraine attack, on the third day of a persistent aura consisting of right hemiplegia and aphasia, PWI revealed hyperperfusion of the left hemisphere. Asymmetry indices for temporal parameters (mean transit time and time to peak) were the most sensitive. These findings resolved spontaneously after the attacks without any permanent sequel or signs of cerebral ischemia on follow-up MRI. PWI should be indicated for patients with migraine attacks accompanied by auras to assess the sequential changes in cerebral perfusion and to better understand its pathogenesis.

17. 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.

18. 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.

19. Perfusion Based Cell Culture Chips

Heiskanen, A.; Emnéus, J.; Dufva, M.

Performing cell culture in miniaturized perfusion chambers gives possibilities to experiment with cells under near in vivo like conditions. In contrast to traditional batch cultures, miniaturized perfusion systems provide precise control of medium composition, long term unattended cultures and tissue like structuring of the cultures. However, as this chapter illustrates, many issues remain to be identified regarding perfusion cell culture such as design, material choice and how to use these systems before they will be widespread amongst biomedical researchers.

20. Review of laser speckle contrast techniques for visualizing tissue perfusion.

PubMed

Draijer, Matthijs; Hondebrink, Erwin; van Leeuwen, Ton; Steenbergen, Wiendelt

2009-07-01

When a diffuse object is illuminated with coherent laser light, the backscattered light will form an interference pattern on the detector. This pattern of bright and dark areas is called a speckle pattern. When there is movement in the object, the speckle pattern will change over time. Laser speckle contrast techniques use this change in speckle pattern to visualize tissue perfusion. We present and review the contribution of laser speckle contrast techniques to the field of perfusion visualization and discuss the development of the techniques.

1. Source confusion as an explanation of cultivation: a test of the mechanisms underlying confusion of fiction with reality on television.

PubMed

Koolstra, Cees M

2007-02-01

Cultivation studies have found evidence that heavy television viewers adopt a world view congruent with how the world is portrayed in fictional television programs. An explanation is that viewers may remember fictional TV stories as realistic stories or news (fiction-to-news confusion). Until now, fiction-to-news confusion was found only if at least a week evolved between watching TV and asking viewers what was remembered. The present study conducted with a purposive sample of students and employees of a college in The Netherlands (N=96; M age = 28.6 yr., SD = 10.9) indicates that fiction-to-news confusions can also occur almost immediately after watching. In addition, whereas earlier research suggests that fiction-to-news confusions are associated with heavy viewing, i.e., more confusion when more hours per day are spent on TV viewing in leisure time, and faulty memory, the present study more specifically suggests that participants make many fiction-to-news confusions when they are exposed to relatively many fictional TV fragments that contain threatening, violent events.

2. 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.

3. Harmonic analysis of perfusion pumps.

PubMed

Dougherty, F Carroll; Donovan, F M; Townsley, Mary I

2003-12-01

The controversy over the use of nonpulsatile versus pulsatile pumps for maintenance of normal organ function during ex vivo perfusion has continued for many years, but resolution has been limited by lack of a congruent mathematical definition of pulsatility. We hypothesized that the waveform frequency and amplitude, as well as the underlying mean distending pressure are all key parameters controlling vascular function. Using discrete Fourier Analysis, our data demonstrate the complexity of the pulmonary arterial pressure waveform in vivo and the failure of commonly available perfusion pumps to mimic in vivo dynamics. In addition, our data show that the key harmonic signatures are intrinsic to the perfusion pumps, are similar for flow and pressure waveforms, and are unchanged by characteristics of the downstream perfusion circuit or perfusate viscosity.

4. Bayesian confusions surrounding simplicity and likelihood in perceptual organization.

PubMed

van der Helm, Peter A

2011-11-01

In the study of perceptual organization, the Occamian simplicity principle (which promotes efficiency) and the Helmholtzian likelihood principle (which promotes veridicality) have been claimed to be equivalent. Proposed models of these principles may well yield similar outcomes (especially in everyday situations), but as argued here, claims that the principles are equivalent confused subjective probabilities (which are used in Bayesian models of the Occamian simplicity principle) and objective probabilities (which are needed in Bayesian models of the Helmholtzian likelihood principle). Furthermore, Occamian counterparts of Bayesian priors and conditionals have led to another confusion, which seems to have been triggered by a dual role of regularity in perception. This confusion is discussed by contrasting complete and incomplete Occamian approaches to perceptual organization. Copyright © 2011 Elsevier B.V. All rights reserved.

5. (abstract) An All Sky Cirrus Confusion Noise Map for WIRE

NASA Technical Reports Server (NTRS)

Gautier, T. N.

1996-01-01

The Wide Field Infrared Explorer (WIRE) is a Small Explorer (SMEX) satellite scheduled for launch in 1998 which will carry out a sky survey of at least 100 square degrees in the wavelength regions of 9-15(micro)m and 21-27(micro)m with spatial resolution of approximately 20 arcsec and sensitivity exceeding 0.6mJy. At this sensitivity level WIRE observations can be seriously affected by the confusion noise contribution from the infrared cirrus emission, so the WIRE survey must be planned with some knowledge of the expected level of cirrus confusion. Production of a cirrus confusion noise map with 0.5 degree resolution based on the spatial power spectral density of the cirrus emission in the IRAS ISSA data is in progess using the method described by Gauthier, et al. Spectrally resolved power spectra density data is obtained from the ISSA maps with a wavelet transform technique.

6. Circle of least confusion of a spherical reflector.

PubMed

Hosken, Robert W

2007-06-01

A simple, tractable equation is provided for determining the size and location of the circle of least confusion of a concave spherical reflector. This method is exact for the object at infinity and with wave effects neglected. Designers of large radius Arecibo-like telescopes, both radio and optical, with symmetrical, spherical primaries should find the method useful. The mathematical results are valid for apertures with an angle of incidence up to 45 degrees. Comparisons of the location of the disk of least confusion with longitudinal spherical aberration and the radius of the disk with transverse spherical aberration are presented.

7. Addressing the Philosophical Confusion Regarding Constructivism in Chemical Education

Bernal, Pedro J.

2006-02-01

In the Chemical Education Today section of the May 2003 issue of this Journal , Eric Scerri wrote about the consequences of what he regards as a philosophical confusion in the work of constructivist chemical education researchers. This issue has important implications for both the teaching and practice of science. I offer a view of the confusion that places the emphasis on the careless use of philosophical terms that Scerri noted and on the tendency of psychological constructivists to go from psychological premises to unwarranted epistemological conclusions.

8. 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

9. Impaired Tissue Oxygenation in Metabolic Syndrome Requires Increased Microvascular Perfusion Heterogeneity.

PubMed

Mason McClatchey, P; Wu, Fan; Olfert, I Mark; Ellis, Christopher G; Goldman, Daniel; Reusch, Jane E B; Frisbee, Jefferson C

2017-02-01

Metabolic syndrome (MS) in obese Zucker rats (OZR) is associated with impaired skeletal muscle performance and blunted hyperemia. Studies suggest that reduced O2 diffusion capacity is required to explain compromised muscle performance and that heterogeneous microvascular perfusion distribution is critical. We modeled tissue oxygenation during muscle contraction in control and OZR skeletal muscle using physiologically realistic relationships. Using a network model of Krogh cylinders with increasing perfusion asymmetry and increased plasma skimming, we predict increased perfusion heterogeneity and decreased muscle oxygenation in OZR, with partial recovery following therapy. Notably, increasing O2 delivery had less impact on VO2 than equivalent decreases in O2 delivery, providing a mechanism for previous empirical work associating perfusion heterogeneity and impaired O2 extraction. We demonstrate that increased skeletal muscle perfusion asymmetry is a defining characteristic of MS and must be considered to effectively model and understand blood-tissue O2 exchange in this model of human disease.

10. The Reign of Confusion: ABC and the "Crisis in Iran."

ERIC Educational Resources Information Center

Palmerton, Patricia R.

A study examined reports broadcast by ABC News between November 8, 1979 and December 7, 1979 in its series entitled "Crisis in Iran: America Held Hostage." Transcripts of approximately 50% of actual broadcasts were subjected to rhetorical critical analysis, from which the finding emerged that confusion was the predominant characteristic…

11. Addressing the Philosophical Confusion Regarding Constructivism in Chemical Education

ERIC Educational Resources Information Center

Bernal, Pedro J.

2006-01-01

In the Chemical Education Today section of the May 2003 issue of the "Journal of Chemical Education," Eric Scerri wrote about the consequences of what he regards as a philosophical confusion in the work of constructivist chemical education researchers. This issue has important implications for both the teaching and practice of science. I offer a…

12. Confusion in the Periodic Table of the Elements.

ERIC Educational Resources Information Center

Fernelius, W. C.; Powell, W. H.

1982-01-01

Discusses long (expanded), short (condensed), and pyramidal periodic table formats and documents events leading to a periodic table in which subgroups (families) are designated with the letters A and B, suggesting that this format is confusing for those consulting the table. (JN)

13. A Test of Confusion Theory of Encoding Specificity

ERIC Educational Resources Information Center

Wiseman, Sandor; Tulving, Endel

1975-01-01

Subjects studied and were tested for recognition and recall of target words on lists of cue-target word pairs. List-cued recall was higher than non-cued recall, suggesting that recognition failure is independent of subjects' familiarity with task requirements. This contradicts attribution of encoding specificity phenomena to subjects' confusion.…

14. Confusion in the Periodic Table of the Elements.

ERIC Educational Resources Information Center

Fernelius, W. C.; Powell, W. H.

1982-01-01

Discusses long (expanded), short (condensed), and pyramidal periodic table formats and documents events leading to a periodic table in which subgroups (families) are designated with the letters A and B, suggesting that this format is confusing for those consulting the table. (JN)

15. John Wilson's Confused "Perspectives on the Philosophy of Education"

ERIC Educational Resources Information Center

Standish, Paul

2006-01-01

In his "Perspectives on the Philosophy of Education" John Wilson laments the confusion that surrounds the current state of the philosophy of education. Unlike other branches of philosophy, he claims, it is not clear what the philosophy of education is about, and a snapshot of current work in the field reveals its lack of coherence. To remedy this…

16. RTI Confusion in the Case Law and the Legal Commentary

ERIC Educational Resources Information Center

Zirkel, Perry A.

2011-01-01

This article expresses the position that the current legal commentary and cases do not sufficiently differentiate response to intervention (RTI) from the various forms of general education interventions that preceded it, thus compounding confusion in professional practice as to legally defensible procedures for identifying children as having a…

17. Addressing the Philosophical Confusion Regarding Constructivism in Chemical Education

ERIC Educational Resources Information Center

Bernal, Pedro J.

2006-01-01

In the Chemical Education Today section of the May 2003 issue of the "Journal of Chemical Education," Eric Scerri wrote about the consequences of what he regards as a philosophical confusion in the work of constructivist chemical education researchers. This issue has important implications for both the teaching and practice of science. I offer a…

18. Women, Education and the Law: Vouchers, Tax Credits, & Legal Confusion

ERIC Educational Resources Information Center

First, Patricia F.

2003-01-01

In early 2003, two distinguished researchers in school law analyzed aspects of the law vis-a-vis vouchers and tax credits and the public schools (McCarthy, 2003; Welner, 2003). The issues were confusing, and the author wondered how educators and the public responded. How can policy makers make reasonable decisions about public education without a…

19. Boson-fermion confusion: the string path to supersymmetry

Ramond, P.

Reminiscences on the String origins of Supersymmetry are followed by a discussion of the importance of confusing bosons with fermions in building superstring theories in 9 + 1 dimensions. In eleven dimensions, the kinship between bosons and fermions is more subtle, and may involve the exceptional group F4.

20. Class and Culture: Sources of Confusion in Educational Sociology

ERIC Educational Resources Information Center

Wrigley, Terry

2013-01-01

This paper reiterates the centrality of economics (relations of production) in Marxist models of class, while avoiding the crude determinism which results from a neglect of cultural aspects of class formation. It explores the confusion in education and educational sociology arising from non-Marxist conceptions of class which place an exaggerated…

1. Confuser rejection performance of EMACH filters for MSTAR ATR

Casasent, David; Nehemiah, Avinash

2006-04-01

Synthetic aperture radar (SAR) automatic target recognition (ATR) based on the extended maximum average correlation height (EMACH) distortion invariant filter (DIF) is presented. Prior work on the EMACH filter addresses 3-class and 10 class classification with clutter rejection. However, the ability of the EMACH filter to reject confusers is not well known. This paper addresses this. We follow a benchmark procedure which involves classification of three object classes over 360° aspect angle differences and with depression angle and variant differences and rejection of two unseen confusers from the Moving and Stationary Target Acquisition and Recognition (MSTAR) public database. We present a scheme to select which training set images to include while making the filters, since it is not necessary to use all training set images to make the filters. Results for classification with both confuser and clutter rejection are presented. We also compare our work with prior EMACH MSTAR work. We find EMACH filters to have poor confuser and clutter rejection. We also correct prior EMACH clutter rejection performance results.

2. On the Conceptual Confusion about Emotional Disorders and Autism.

ERIC Educational Resources Information Center

Nomura, Tosuke

1987-01-01

There has been serious confusion between the terms "infantile autism" and "emotional disorders" in Japan, especially as pertains to special education classes. Special classes for emotionally disturbed children began in Japan in 1969 with a rapid increase to over 2000 classes by the 1980's. However, most of the children…

3. Class and Culture: Sources of Confusion in Educational Sociology

ERIC Educational Resources Information Center

Wrigley, Terry

2013-01-01

This paper reiterates the centrality of economics (relations of production) in Marxist models of class, while avoiding the crude determinism which results from a neglect of cultural aspects of class formation. It explores the confusion in education and educational sociology arising from non-Marxist conceptions of class which place an exaggerated…

4. Alleviating the Common Confusion Caused by Polarity in Electrochemistry.

ERIC Educational Resources Information Center

1989-01-01

Discussed is some of the confusion encountered in electrochemistry due to misunderstandings of sign conventions and simple mathematical errors. Clarified are issues involving emf series, IUPAC sign conventions, calculation of cell potentials, reference electrodes, the polarity of electrodes in electrochemical devices, and overpotential. (CW)

5. Predator confusion is sufficient to evolve swarming behaviour

PubMed Central

Olson, Randal S.; Hintze, Arend; Dyer, Fred C.; Knoester, David B.; Adami, Christoph

2013-01-01

Swarming behaviours in animals have been extensively studied owing to their implications for the evolution of cooperation, social cognition and predator–prey dynamics. An important goal of these studies is discerning which evolutionary pressures favour the formation of swarms. One hypothesis is that swarms arise because the presence of multiple moving prey in swarms causes confusion for attacking predators, but it remains unclear how important this selective force is. Using an evolutionary model of a predator–prey system, we show that predator confusion provides a sufficient selection pressure to evolve swarming behaviour in prey. Furthermore, we demonstrate that the evolutionary effect of predator confusion on prey could in turn exert pressure on the structure of the predator's visual field, favouring the frontally oriented, high-resolution visual systems commonly observed in predators that feed on swarming animals. Finally, we provide evidence that when prey evolve swarming in response to predator confusion, there is a change in the shape of the functional response curve describing the predator's consumption rate as prey density increases. Thus, we show that a relatively simple perceptual constraint—predator confusion—could have pervasive evolutionary effects on prey behaviour, predator sensory mechanisms and the ecological interactions between predators and prey. PMID:23740485

6. Perfusion measurement in acute pancreatitis using dynamic perfusion MDCT.

PubMed

Bize, Pierre E; Platon, Alexandra; Becker, Christoph D; Poletti, Pierre-Alexandre

2006-01-01

Our objective was to determine whether MDCT with perfusion imaging could help in assessing the severity of acute pancreatitis in the initial phase of the disease. One hundred six patients with abdominal pain were prospectively enrolled in this study. Patients were separated into two groups: P1 (severe) and P2 (mild) acute pancreatitis. Mean perfusion value was 24.8 mL/100 mL/min in the P1 group and 50.5 mL/100 mL/min in the P2 group (p = 0.0016, significant). Our preliminary data suggest that pancreatic perfusion measurement using MDCT with perfusion imaging could help in assessing the severity of acute pancreatitis.

7. Cerebral-Body Perfusion Model

DTIC Science & Technology

1990-07-01

compared to the 0.5g curve) fall in flow. Fig. 9b, showing the 5g case, strongly suggests a possible, so-called, " luxury perfusion ", in which natural...as the luxury perfusion situation which bypasses the flow with the nutrients it carries (through newly opened collaterals) and result in a "blackout...89-0054 CEREBRAL-BODY PERFUSION MODEL S. Sorek’, J. Bear2, and M., Feinsod3 in Collaboration with K. Allen4, L. Bunt5 and S. Ben-IHaiM6 July 1990

8. Distributed Perfusion Educational Model: A Shift in Perfusion Economic Realities

PubMed Central

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

2005-01-01

Abstract: 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

9. Pulmonary ventilation/perfusion scan

MedlinePlus

... JavaScript. A pulmonary ventilation/perfusion scan involves two nuclear scan tests to measure breathing (ventilation) and circulation ( ... In: Mettler FA, Guiberteau MJ, eds. Essentials of Nuclear Medicine Imaging . 6th ed. Philadelphia, PA: Elsevier Saunders; ...

10. Nifedipine increases fetoplacental perfusion.

PubMed

Karahanoglu, Ertugrul; Altinboga, Orhan; Akpinar, Funda; Demirdag, Erhan; Ozdemirci, Safak; Akyol, Aysegul; Yalvac, Serdar

2017-01-01

Our aim is to evaluate the effect of nifedipine on fetoplacental hemodynamic parameters. A retrospective study was conducted at a tertiary center with 30 patients for whom nifedipine treatment was used as a tocolytic therapy for preterm labor. Initiation of this treatment was at 31.6±2.5 weeks of gestation. We combined the pulse Doppler imaging parameters with grayscale imaging via the Bernoulli theorem, which is called the "continuity equation", to get the fetoplacental perfusion (FPP). Evaluated parameters were the resistance index (RI), the pulsatility index (PI), systole/diastole ratios (S/D), the velocity-time integral of the umbilical artery (VTI), the radius of the umbilical artery, the peak systolic velocity and the mean pressure gradient in the umbilical artery. From these parameters, the FPP was acquired. We found that the RI, the PI and the S/D ratio did not change after treatment with nifedipine. The mean pressure gradient, the VTI and the peak systolic velocity increased after treatment with nifedipine. Nifedipine increases FPP from 166±73.81 beat.cm3/min to 220±83.3 beat.cm3/min. Although nifedipine had no effect on the PI, the RI or the S/D, it increased the mean pressure gradient, the VTI and FPP.

Storm, Corstiaan J.; Slump, Cornelis H.

2007-03-01

Our purpose is in the automated evaluation of the physiological relevance of lesions in coronary angiograms. We aim to extract as much as possible quantitative information about the physiological condition of the heart from standard angiographic image sequences. Coronary angiography is still the gold standard for evaluating and diagnosing coronary abnormalities as it is able to locate precisely the coronary artery lesions. The dimensions of the stenosis can be assessed nowadays successfully with image processing based Quantitative Coronary Angiography (QCA) techniques. Our purpose is to assess the clinical relevance of the pertinent stenosis. We therefore analyze the myocardial perfusion as revealed in standard angiographic image sequences. In a Region-of-Interest (ROI) on the angiogram (without an overlaying major blood vessel) the contrast is measured as a function of time (the so-called time-density curve). The required hyperemic state of exercise is induced artificially by the injection of a vasodilator drug e.g. papaverine. In order to minimize motion artifacts we select based on the recorded ECG signal end-diastolic images in both a basal and a hyperemic run in the same projection to position the ROI. We present the development of the algorithms together with results of a small study of 20 patients which have been catheterized following the standard protocol.

12. Computed tomography perfusion imaging in spectacular shrinking deficit.

PubMed

Lee, Vivien H; John, Sayona; Mohammad, Yousef; Prabhakaran, Shyam

2012-02-01

Spectacular shrinking deficit (SSD) is characterized by abrupt onset of a major hemispheric stroke syndrome, followed by dramatic and rapid improvement. We retrospectively identified patients with SSD diagnosed at our institution between December 1, 2007, and June 30, 2009. We reviewed computed tomography perfusion (CTP) imaging to determine perfusion defect as a measure of initial ischemic penumbra, and magnetic resonance imaging diffusion-weighted imaging (DWI) to determine the final infarct core. Among the 472 consecutive ischemic stroke patients, 126 (27%) presented with major hemispheric ischemic stroke syndrome, defined as National Institutes of Health Stroke Scale score (NIHSS) ≥8 in the territory of the middle cerebral artery (MCA) or internal carotid artery (ICA). Out of these patients, we identified 8 SSD patients with available CTP data. In these 8 patients, the mean time to dramatic recovery was 3.4 hours (range, 0.75-7 hours), and the mean time from onset to CTP was 12.7 hours (range, 3-30 hours). All 8 patients had perfusion abnormalities in portions of the MCA territory (partial MCA territory in 5 patients and complete MCA territory in 3 patients). The mean time from onset to MRI DWI was 15.5 hours (range, 7.9-34 hours). Restricted diffusion was present in all patients in the corresponding MCA distribution. Vascular imaging revealed MCA occlusion in 2 patients. Cervical vascular imaging revealed carotid occlusion in 2 patients and high-grade carotid stenosis in 2 patients. The stroke mechanisms were cardioembolism in 2 patients, large artery in 4 patients, and unknown in 2 patients. Four patients had repeat CTP imaging available that demonstrated eventual resolution of the perfusion defect. SSD is associated with a "shrinking" clinical syndrome and a "shrinking" perfusion pattern on CTP that lags behind clinical recovery. CTP imaging corroborates that a larger territory is at risk in SSD and contributes to better understanding of SSD.

13. Measuring velocity and temperature profile sectional pipeline behind confuser

Siažik, Ján; Malcho, Milan; Lenhard, Richard; Novomestský, Marcel

2016-06-01

The article deals with the measuring of temperature and velocity profile in area behind confuser in real made scale model of bypass. For proper operation of the equipment it is necessary to know the actual flow in the pipe. Bypasses have wide application and can be also associated with devices for heat recovery, heat exchangers different designs in which may be used in certain circumstances. In the present case, the heat that would otherwise has not been used is used for heating of insulators, and heating the air in the spray-dryer. The measuring principle was verify how the above-mentioned temperature and velocity profile decomposition above confuser on real made scale model.

14. Why is Alzheimer disease confused with other dementias?

PubMed

Aygün, Dursun; Güngör, Ibrahim Levent

2015-01-01

15. Confusion Noise Level Due to Galactic and Extragalactic Binaries

NASA Technical Reports Server (NTRS)

Bender, Peter L.; Hils, Dieter

1997-01-01

We have revised our earlier rough estimate of the combined galactic and extragalactic binary confusion noise level curve for gravitational waves. This was done to correct some numerical errors and to allow for roughly three frequency bins worth of information about weaker sources being lost for each galactic binary signal that is removed from the data. The results are still based on the spectral amplitude estimates for different types of galactic binaries reported by Hils et al in 1990, and assume that the gravitational wave power spectral densities for other galaxies are proportional to the optical luminosities. The estimated confusion noise level drops to the LISA instrumental noise level at between roughly 3 and 8 MHz.

16. Computation of the disk of least confusion for conic mirrors.

PubMed

Castro-Ramos, Jorge; de Prieto, Oscar Ita; Silva-Ortigoza, Gilberto

2004-11-20

We use geometrical optics to compute, in an exact way and by using the third-order approximation, the disk of least confusion (DLC) or the best image produced by a conic reflector when the point source is located at any position on the optical axis. In the approximate case we obtain analytical formulas to compute the DLC. Furthermore, we apply our equations to particular examples to compare the exact and approximate results.

17. A Procedure for Verifying Security Against Type Confusion Attacks

DTIC Science & Technology

2003-01-01

certificate containing the public key, and hence the possession of any identity or privileges stored in that certificate. As for the Groupkey Push...principals who possess information and can check properties of data based on that information. As in the Dolev-Yao model, we assume principals are either...itd.nrl.navy.mil Abstract A type confusion attack is one in which a principal ac- cepts data of one type as data of another. Although it has been

18. Consonant confusions for temporally smeared envelope of syllables in noise

Yoon, Yang-Soo; Gooler, David; Allen, Jont

2005-09-01

The purpose of this study was to better understand the contribution of speech temporal envelope cues to consonant recognition in noise (-8, 0, 8, 16, 24, and quiet dB SNR). Four tasks were performed for hearing-impaired listeners: Speech-in-Noise test for the measure of sentence repeat ability in noise, gap and intensity detection for the measure of ability to detect changes in sound over time, and consonant identification for confusion matrices. For consonant identification, the temporal envelope of 16 consonants with a vowel /a/ (CV) was extracted from each of 26 critical bands. Each processed CV was temporally smeared by low-pass filtering (4, 8, and 16 Hz). The results show that the mean Pc increases gradually as SNR increases SNR < 16 dB for all conditions, but decreases at SNR > 16 dB for no-smearing and 8-Hz smearing conditions. Consonant confusions result from certain sets of consonants, but the degree of confusion is a function of SNR. The results also show that measures of Speech-in-Noise and gap detection are more related to pure-tone threshold, while intensity detection is less related to pure-tone threshold. However, the effect of interstimulus interval is consistent regardless of degree and configuration of hearing loss.

19. Detecting Mode Confusion Through Formal Modeling and Analysis

NASA Technical Reports Server (NTRS)

Miller, Steven P.; Potts, James N.

1999-01-01

Aircraft safety has improved steadily over the last few decades. While much of this improvement can be attributed to the introduction of advanced automation in the cockpit, the growing complexity of these systems also increases the potential for the pilots to become confused about what the automation is doing. This phenomenon, often referred to as mode confusion, has been involved in several accidents involving modern aircraft. This report describes an effort by Rockwell Collins and NASA Langley to identify potential sources of mode confusion through two complementary strategies. The first is to create a clear, executable model of the automation, connect it to a simulation of the flight deck, and use this combination to review of the behavior of the automation and the man-machine interface with the designers, pilots, and experts in human factors. The second strategy is to conduct mathematical analyses of the model by translating it into a formal specification suitable for analysis with automated tools. The approach is illustrated by applying it to a hypothetical, but still realistic, example of the mode logic of a Flight Guidance System.

20. Spectral Line De-confusion in an Intensity Mapping Survey

Cheng, Yun-Ting; Chang, Tzu-Ching; Bock, James; Bradford, C. Matt; Cooray, Asantha

2016-12-01

Spectral line intensity mapping (LIM) has been proposed as a promising tool to efficiently probe the cosmic reionization and the large-scale structure. Without detecting individual sources, LIM makes use of all available photons and measures the integrated light in the source confusion limit to efficiently map the three-dimensional matter distribution on large scales as traced by a given emission line. One particular challenge is the separation of desired signals from astrophysical continuum foregrounds and line interlopers. Here we present a technique to extract large-scale structure information traced by emission lines from different redshifts, embedded in a three-dimensional intensity mapping data cube. The line redshifts are distinguished by the anisotropic shape of the power spectra when projected onto a common coordinate frame. We consider the case where high-redshift [C ii] lines are confused with multiple low-redshift CO rotational lines. We present a semi-analytic model for [C ii] and CO line estimates based on the cosmic infrared background measurements, and show that with a modest instrumental noise level and survey geometry, the large-scale [C ii] and CO power spectrum amplitudes can be successfully extracted from a confusion-limited data set, without external information. We discuss the implications and limits of this technique for possible LIM experiments.

1. Ultrafast spectroscopy of free-base N-confused tetraphenylporphyrins.

PubMed

Alemán, Elvin A; Rajesh, Cheruvallil S; Ziegler, Christopher J; Modarelli, David A

2006-07-20

The photophysical characterization of the two tautomers (1e and 1i) of 5,10,15,20-tetraphenyl N-confused free-base porphyrin, as well as the tautomer-locked 2-methyl 5,10,15,20-tetraphenyl N-confused free-base porphyrin, was carried out using a combination of steady state and time-resolved optical techniques. N-Confused porphyrins, alternatively called 2-aza-21-carba-porphyrins or inverted porphyrins, are of great interest for their potential as building blocks in assemblies designed for artificial photosynthesis, and understanding their excited-state properties is paramount to future studies in multicomponent arrays. Femtosecond resolved transient absorption experiments reveal spectra that are similar to those of tetraphenylporphyrin (H2TPP) with either Soret or Q-band excitation, with an extinction coefficient for the major absorbing band of 1e that was about a factor of 5 larger than that of H2TPP. The lifetime of the S1 state was determined at a variety of absorption wavelengths for each compound and was found to be consistent with time-resolved fluorescence experiments. These experiments reveal that the externally protonated tautomer (1e) is longer lived (tau = 1.84 ns) than the internally protonated form (1i, tau = 1.47 ns) by approximately 369 ps and that the N-methyl N-confused porphyrin was shorter lived than the tautomeric forms by approximately 317 ps (DMAc) and approximately 396 ps (benzene). Steady-state fluorescence experiments on tautomers 1e and 1i and the N-methyl analogues corroborate these results, with fluorescence quantum yields (Phi(Fl)) of 0.046 (1e, DMAc) and 0.023 (1i, benzene), and 0.025 (DMAc) and 0.018 (benzene) for the N-methyl N-confused porphyrin. The lifetime and quantum yield data was interpreted in terms of structural changes that influence the rate of internal conversion. The absorption and transient absorption spectra of these porphyrins were also examined in the context of DFT calculations at the B3LYP/6-31G(d)//B3LYP/3-21G

2. Effects and modeling of phonetic and acoustic confusions in accented speech

Fung, Pascale; Liu, Yi

2005-11-01

Accented speech recognition is more challenging than standard speech recognition due to the effects of phonetic and acoustic confusions. Phonetic confusion in accented speech occurs when an expected phone is pronounced as a different one, which leads to erroneous recognition. Acoustic confusion occurs when the pronounced phone is found to lie acoustically between two baseform models and can be equally recognized as either one. We propose that it is necessary to analyze and model these confusions separately in order to improve accented speech recognition without degrading standard speech recognition. Since low phonetic confusion units in accented speech do not give rise to automatic speech recognition errors, we focus on analyzing and reducing phonetic and acoustic confusability under high phonetic confusion conditions. We propose using likelihood ratio test to measure phonetic confusion, and asymmetric acoustic distance to measure acoustic confusion. Only accent-specific phonetic units with low acoustic confusion are used in an augmented pronunciation dictionary, while phonetic units with high acoustic confusion are reconstructed using decision tree merging. Experimental results show that our approach is effective and superior to methods modeling phonetic confusion or acoustic confusion alone in accented speech, with a significant 5.7% absolute WER reduction, without degrading standard speech recognition.

3. 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

4. Modeling of nanotherapeutics delivery based on tumor perfusion

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.

5. Assessment of foot perfusion in patients with a diabetic foot ulcer.

PubMed

Forsythe, Rachael O; Hinchliffe, Robert J

2016-01-01

Assessment of foot perfusion is a vital step in the management of patients with diabetic foot ulceration, in order to understand the risk of amputation and likelihood of wound healing. Underlying peripheral artery disease is a common finding in patients with foot ulceration and is associated with poor outcomes. Assessment of foot perfusion should therefore focus on identifying the presence of peripheral artery disease and to subsequently estimate the effect this may have on wound healing. Assessment of perfusion can be difficult because of the often complex, diffuse and distal nature of peripheral artery disease in patients with diabetes, as well as poor collateralisation and heavy vascular calcification. Conventional methods of assessing tissue perfusion in the peripheral circulation may be unreliable in patients with diabetes, and it may therefore be difficult to determine the extent to which poor perfusion contributes to foot ulceration. Anatomical data obtained on cross-sectional imaging is important but must be combined with measurements of tissue perfusion (such as transcutaneous oxygen tension) in order to understand the global and regional perfusion deficit present in a patient with diabetic foot ulceration. Ankle-brachial pressure index is routinely used to screen for peripheral artery disease, but its use in patients with diabetes is limited in the presence of neuropathy and medial arterial calcification. Toe pressure index may be more useful because of the relative sparing of pedal arteries from medial calcification but may not always be possible in patients with ulceration. Fluorescence angiography is a non-invasive technique that can provide rapid quantitative information about regional tissue perfusion; capillaroscopy, iontophoresis and hyperspectral imaging may also be useful in assessing physiological perfusion but are not widely available. There may be a future role for specialized perfusion imaging of these patients, including magnetic resonance

6. CT perfusion evidence of early global cerebral hypoperfusion after aneurysmal subarachnoid hemorrhage with cardiac arrest.

PubMed

Burns, Joseph D; Jacob, Jeffrey T; Luetmer, Patrick H; Wijdicks, Eelco F M

2010-04-01

Cardiac arrest and aneurysmal subarachnoid hemorrhage both cause sudden, severe cerebral hypoperfusion at ictus. Animal studies indicate that the resultant microvascular dysfunction and cerebral perfusion abnormalities are important determinants of the associated cerebral injury in both conditions. Although this suggests that perfusion imaging might be a useful tool for prognostication in patients with these conditions, this hypothesis has not been thoroughly investigated in humans. Case report. A 49-year-old man developed cardiac arrest upon rupture of an intracranial aneurysm. When he arrived at our institution 10 h later, he was comatose, had neurogenic hyperventilation, absent corneal reflexes, and continuous multifocal myoclonus. Despite normal intracranial pressure, normal cerebral perfusion pressure, normal flow in the proximal cerebral arteries on CT angiography, and a lack of diffuse cerebral edema, CT perfusion imaging performed 12 h after ictus showed severe, diffuse hypoperfusion. After the development of refractory intracranial hypertension, physiologic support was withdrawn and the patient died. Early global cerebral hypoperfusion can be demonstrated by CT perfusion imaging after cardiac arrest associated with high-grade aneurysmal subarachnoid hemorrhage and may be indicative of poor neurologic outcome. CT perfusion should be investigated as a prognostic tool in these conditions.

7. Viable neurons with luxury perfusion in hydrocephalus.

PubMed

Wong, C Y; Luciano, M G; MacIntyre, W J; Brunken, R C; Hahn, J F; Go, R T

1997-09-01

A woman with hydrocephalus due to aqueductal stenosis had functional imaging of cerebral perfusion and metabolism to demonstrate the effects of endoscopic third ventriculostomy--a new form of internal surgical shunting. Technetium-99m-ECD SPECT and 18F-FDG PET showed regional luxury perfusion at the left frontal region. Three months after a successful third ventriculostomy, a repeated imaging of cerebral perfusion and metabolism showed resolution of luxury perfusion and global improvement of both perfusion and metabolism. This concurred with postoperative clinical improvement. The paired imaging of cerebral perfusion and metabolism provides more information than just imaging perfusion or metabolism. Thus, the detection of perfusion and metabolism mismatch may open a new window of opportunity for surgical intervention.

8. Perception and confusion of speech sounds by adults with a cochlear implant.

PubMed

Rødvik, Arne K

2008-01-01

The aim of this pilot study was to identify the most common speech sound confusions of 5 Norwegian cochlear implanted post-lingually deafened adults. We played recorded nonwords, aCa, iCi and bVb, to our informants, asked them to repeat what they heard, recorded their repetitions and transcribed these phonetically. We arranged the collected data in confusion matrices to find the most common and most uncommon speech sound confusions. We found that the voiced and unvoiced consonants are seldom confused. We also found that there was a higher rate of consonant confusion for the iCi words than for the aCa words. The most frequent confusion was [eta] perceived as [n], [m] perceived as [n] and [upsilon] perceived as [n]. For the consonants, manner of articulation was rarely confused, but place of articulation was often confused. An exception from this was the confusion of [l] and [n], which differs only in manner of articulation. The latter is in accordance with reports we get from clinicians. We postulate that this is caused by the speech processing of the cochlear implant. We found less confusion of the vowels, which can be explained by the fact that vowels have much higher energy and longer duration than most of the consonants. The most frequent confusion was [a:] perceived as [see text] and [u:] perceived as [see text]. [e:], [i:] and [see text] were never confused with other vowels.

9. Spectral Confusion for Cosmological Surveys of Redshifted C II Emission

NASA Technical Reports Server (NTRS)

Kogut, A.; Dwek, E.; Moseley, S. H.

2015-01-01

Far-infrared cooling lines are ubiquitous features in the spectra of star-forming galaxies. Surveys of redshifted fine-structure lines provide a promising new tool to study structure formation and galactic evolution at redshifts including the epoch of reionization as well as the peak of star formation. Unlike neutral hydrogen surveys, where the 21 cm line is the only bright line, surveys of redshifted fine-structure lines suffer from confusion generated by line broadening, spectral overlap of different lines, and the crowding of sources with redshift. We use simulations to investigate the resulting spectral confusion and derive observing parameters to minimize these effects in pencilbeam surveys of redshifted far-IR line emission. We generate simulated spectra of the 17 brightest far-IR lines in galaxies, covering the 150-1300 µm wavelength region corresponding to redshifts 0 < z < 7, and develop a simple iterative algorithm that successfully identifies the 158 µm [C II] line and other lines. Although the [C II] line is a principal coolant for the interstellar medium, the assumption that the brightest observed lines in a given line of sight are always [C II] lines is a poor approximation to the simulated spectra once other lines are included. Blind line identification requires detection of fainter companion lines from the same host galaxies, driving survey sensitivity requirements. The observations require moderate spectral resolution 700 < R < 4000 with angular resolution between 20? and 10', sufficiently narrow to minimize confusion yet sufficiently large to include a statistically meaningful number of sources.

10. SPECTRAL CONFUSION FOR COSMOLOGICAL SURVEYS OF REDSHIFTED C II EMISSION

SciTech Connect

Kogut, A.; Dwek, E.; Moseley, S. H.

2015-06-20

Far-infrared cooling lines are ubiquitous features in the spectra of star-forming galaxies. Surveys of redshifted fine-structure lines provide a promising new tool to study structure formation and galactic evolution at redshifts including the epoch of reionization as well as the peak of star formation. Unlike neutral hydrogen surveys, where the 21 cm line is the only bright line, surveys of redshifted fine-structure lines suffer from confusion generated by line broadening, spectral overlap of different lines, and the crowding of sources with redshift. We use simulations to investigate the resulting spectral confusion and derive observing parameters to minimize these effects in pencil-beam surveys of redshifted far-IR line emission. We generate simulated spectra of the 17 brightest far-IR lines in galaxies, covering the 150–1300 μm wavelength region corresponding to redshifts 0 < z < 7, and develop a simple iterative algorithm that successfully identifies the 158 μm [C ii] line and other lines. Although the [C ii] line is a principal coolant for the interstellar medium, the assumption that the brightest observed lines in a given line of sight are always [C ii] lines is a poor approximation to the simulated spectra once other lines are included. Blind line identification requires detection of fainter companion lines from the same host galaxies, driving survey sensitivity requirements. The observations require moderate spectral resolution 700 < R < 4000 with angular resolution between 20″ and 10′, sufficiently narrow to minimize confusion yet sufficiently large to include a statistically meaningful number of sources.

11. Spectral Confusion for Cosmological Surveys of Redshifted C II Emission

NASA Technical Reports Server (NTRS)

Kogut, A.; Dwek, E.; Moseley, S. H.

2015-01-01

Far-infrared cooling lines are ubiquitous features in the spectra of star-forming galaxies. Surveys of redshifted fine-structure lines provide a promising new tool to study structure formation and galactic evolution at redshifts including the epoch of reionization as well as the peak of star formation. Unlike neutral hydrogen surveys, where the 21 cm line is the only bright line, surveys of redshifted fine-structure lines suffer from confusion generated by line broadening, spectral overlap of different lines, and the crowding of sources with redshift. We use simulations to investigate the resulting spectral confusion and derive observing parameters to minimize these effects in pencilbeam surveys of redshifted far-IR line emission. We generate simulated spectra of the 17 brightest far-IR lines in galaxies, covering the 150-1300 µm wavelength region corresponding to redshifts 0 < z < 7, and develop a simple iterative algorithm that successfully identifies the 158 µm [C II] line and other lines. Although the [C II] line is a principal coolant for the interstellar medium, the assumption that the brightest observed lines in a given line of sight are always [C II] lines is a poor approximation to the simulated spectra once other lines are included. Blind line identification requires detection of fainter companion lines from the same host galaxies, driving survey sensitivity requirements. The observations require moderate spectral resolution 700 < R < 4000 with angular resolution between 20? and 10', sufficiently narrow to minimize confusion yet sufficiently large to include a statistically meaningful number of sources.

12. Yield of CT perfusion for the evaluation of transient ischaemic attack.

PubMed

Kleinman, Jonathan T; Mlynash, Michael; Zaharchuk, Greg; Ogdie, Alyshia A; Straka, Matus; Lansberg, Maarten G; Schwartz, Neil E; Singh, Paul; Kemp, Stephanie; Bammer, Roland; Albers, Gregory W; Olivot, Jean-Marc

2015-10-01

Magnetic resonance diffusion-weighted imaging and perfusion-weighted imaging are able to identify ischaemic 'footprints' in transient ischaemic attack. Computed tomography perfusion (CTP) may be useful for patient triage and subsequent management. To date, less than 100 cases have been reported, and none have compared computed tomography perfusion to perfusion-weighted imaging (PWI). We sought to define the yield of computed tomography perfusion for the evaluation of transient ischaemic attack. Consecutive patients with a discharge diagnosis of possible or definite transient ischaemic event who underwent computed tomography perfusion were included in this study. The presence of an ischaemic lesion was assessed on noncontrast computed tomography, automatically deconvolved CTPTMax (Time till the residue function reaches its maximum), and when available on diffusion-weighted imaging and PWITMax maps. Thirty-four patients were included and 17 underwent magnetic resonance imaging. Median delay between onset and computed tomography perfusion was 4·4 h (Interquartile range [IQR]: 1·9-9·6), and between computed tomography perfusion and magnetic resonance imaging was 11 h (Interquartile range: 3·8-22). Noncontrast computed tomography was negative in all cases, while CTPTMax identified an ischaemic lesion in 12/34 patients (35%). In the subgroup of patients with multimodal magnetic resonance imaging, an ischaemic lesion was found in six (35%) patients using CTPTMax versus nine (53%) on magnetic resonance imaging (five diffusion-weighted imaging, nine perfusion-weighted imaging). The additional yield of CTPTMax over computed tomography angiography was significant in the evaluation of transient ischaemic attack (12 vs. 3, McNemar, P = 0·004). CTPTMax found an ischaemic lesion in one-third of acute transient ischaemic attack patients. Computed tomography perfusion may be an acceptable substitute when magnetic resonance imaging is unavailable or contraindicated, and

13. Bilateral basal Xe-133 retention and ventilation/perfusion patterns in mild and subclinical congestive heart failure

SciTech Connect

Lee, H.K.; Skarzynski, J.J.; Spadaro, A. )

1989-12-01

The Xe-133 ventilation pattern in congestive heart failure (CHF) was assessed using 24 inpatient ventilation/perfusion studies performed to rule out pulmonary embolism. Patients with histories of CHF, myocardial infarction (MI), and cardiomyopathy were included in the study. Frank pulmonary edema, pulmonary embolism, and other known lung diseases such as chronic obstructive lung disease, tumor, and pneumonia were excluded. Fifteen of the 24 patients had abnormal ventilation scans. Twelve of the 15 showed bilateral basal Xe-133 retention on washout; the remaining 3 showed diffuse, posterior regional retention. On perfusion scans, 14 of the 15 abnormal ventilation patients showed evidence of CHF such as inverted perfusion gradient, enlarged cardiac silhouette, or patchy perfusion, and all of them had a history of CHF or cardiac disease. Nine of the 24 patients had normal ventilation scans, including normal washout patterns. Seven of the nine had normal perfusion (p less than 0.01). Four of the nine normal ventilation patients had a history of cardiac disease or CHF but no recent acute MI. Bilateral basal regional Xe-133 retention, coupled with perfusion scan evidence of CHF such as inverted perfusion gradient, enlarged cardiac silhouette, and patchy perfusion pattern, appears to be a sensitive and characteristic ventilation/perfusion finding in mild or subclinical CHF.

14. Harvest of confusion: immigration reform and California agriculture.

PubMed

Martin, P L

1990-01-01

"Agriculture was a major stumbling block to immigration reform [in the United States], largely because Congress was unwilling to assign explicit priorities to the competing goals of protecting American workers and admitting supplemental immigrant farmworkers. This article describes the Special Agricultural Worker or SAW legalization program that generated 700,000 applications in California and the hypothetical calculations required to determine whether Replenishment Agricultural Workers or RAWs will be admitted to the United States to do farmwork. The paper concludes that immigration reform did not resolve the century-old debate over agriculture's 'need' for alien workers; instead, SAWs and RAWs have contributed to the harvest of confusion on farm labor."

15. MALPOSITIONED LMA CONFUSED AS FOREIGN BODY IN NASAL CAVITY.

PubMed

Verma, Sidharth; Mehta, Nitika; Mehta, Nandita; Mehta, Satish; Verma, Jayeeta

2015-10-01

We present a case of confusing white foreign body in the nasal cavity detected during Endoscopic Sinus Surgery (ESS) in a 35-yr-old male which turned out to be a malposition of classic laryngeal mask airway (LMA). Although malposition of LMA is a known entity to the anesthesiologist, if ventilation is adequate, back folded LMA in nasal cavity might not be recognized by the surgeon and lead to catastrophic consequences during endoscopic sinus surgery. In principle, misfolding and malpositioning can be reduced by pre usage testing, using appropriate sizes, minimizing cuff volume, and early identification and correction of malposition.

16. Biotechnology patents: new move confuses US patents world.

PubMed

Budiansky, Stephen

1983-03-17

Patent attorneys are perplexed and dismayed over a surprise decision by the U.S. Patent Office to drop its earlier objections to the second Cohen-Boyer patent application, covering basic processes in recombinant DNA technology. The patent proceedings, which were closed to public access at the request of Stanford University, have resulted in confusion over the meaning of the patent law's disclosure requirement as it applies to new organisms. Meanwhile, evidence of a prior Ph.D. thesis has called into question the originality of the Cohen-Boyer process.

17. Toxic shock syndrome. Possible confusion with Kawasaki's disease.

PubMed

Raimer, S S; Tschen, E H; Walker, M K

1981-07-01

Toxic shock syndrome (TSS) is a recently recognized condition associated with toxin-producing strains of Staphylococcus aureus. Patients affected with this syndrome are frequently young and have multisystemic complaints such as fever, headache, edema, myalgia, scarlatiniform rash, conjunctival injection, confusion, diarrhea, oliguria, hypotension and shock, This is followed by desquamation of the skin, especially the palms and soles. The majority of cases reported have been in menstruating women who used vaginal tampons regularly. Because similarities exist between toxic shock syndrome and Kawasaki's disease (mucocutaneous lymph node syndrome), as well as other conditions, proper diagnosis and management are of the utmost importance.

18. A Formal Methods Approach to the Analysis of Mode Confusion

NASA Technical Reports Server (NTRS)

Butler, Ricky W.; Miller, Steven P.; Potts, James N.; Carreno, Victor A.

2004-01-01

The goal of the new NASA Aviation Safety Program (AvSP) is to reduce the civil aviation fatal accident rate by 80% in ten years and 90% in twenty years. This program is being driven by the accident data with a focus on the most recent history. Pilot error is the most commonly cited cause for fatal accidents (up to 70%) and obviously must be given major consideration in this program. While the greatest source of pilot error is the loss of situation awareness , mode confusion is increasingly becoming a major contributor as well. The January 30, 1995 issue of Aviation Week lists 184 incidents and accidents involving mode awareness including the Bangalore A320 crash 2/14/90, the Strasbourg A320 crash 1/20/92, the Mulhouse-Habsheim A320 crash 6/26/88, and the Toulouse A330 crash 6/30/94. These incidents and accidents reveal that pilots sometimes become confused about what the cockpit automation is doing. Consequently, human factors research is an obvious investment area. However, even a cursory look at the accident data reveals that the mode confusion problem is much deeper than just training deficiencies and a lack of human-oriented design. This is readily acknowledged by human factors experts. It seems that further progress in human factors must come through a deeper scrutiny of the internals of the automation. It is in this arena that formal methods can contribute. Formal methods refers to the use of techniques from logic and discrete mathematics in the specification, design, and verification of computer systems, both hardware and software. The fundamental goal of formal methods is to capture requirements, designs and implementations in a mathematically based model that can be analyzed in a rigorous manner. Research in formal methods is aimed at automating this analysis as much as possible. By capturing the internal behavior of a flight deck in a rigorous and detailed formal model, the dark corners of a design can be analyzed. This paper will explore how formal

19. Percutaneous malathion absorption in the harvested perfused anuran pelvic limb.

PubMed

Willens, Scott; Stoskopf, Michael K; Baynes, Ronald E; Lewbart, Gregory A; Taylor, Sharon K; Kennedy-Stoskopf, Suzanne

2006-11-01

The objective of this study was to establish an accurate in vitro model for cutaneous absorption in anurans. The harvested perfused anuran pelvic limb (HPAPL) model maintains the anatomic and physiologic integrity of the skin from the pelvic limb, including the intact capillary network. Radiolabeled malathion was applied to the skin of the dorsal thigh, and perfusate was collected over a 6h period. Residues from the skin surface, stratum externum, and dosed area beneath the stratum externum were analyzed. Kinetic parameters were calculated from these data. Absorption was significantly less for the HPAPL than previously reported for Teflon flow-through diffusion cells. However, partitioning effects were comparable. The HPAPL is an appropriate in vitro model for examining cutaneous absorption kinetics in the bullfrog.

20. Blood-brain barrier permeability imaging using perfusion computed tomography

PubMed Central

Avsenik, Jernej; Bisdas, Sotirios; Popovic, Katarina Surlan

2015-01-01

Background. The blood-brain barrier represents the selective diffusion barrier at the level of the cerebral microvascular endothelium. Other functions of blood-brain barrier include transport, signaling and osmoregulation. Endothelial cells interact with surrounding astrocytes, pericytes and neurons. These interactions are crucial to the development, structural integrity and function of the cerebral microvascular endothelium. Dysfunctional blood-brain barrier has been associated with pathologies such as acute stroke, tumors, inflammatory and neurodegenerative diseases. Conclusions. Blood-brain barrier permeability can be evaluated in vivo by perfusion computed tomography - an efficient diagnostic method that involves the sequential acquisition of tomographic images during the intravenous administration of iodinated contrast material. The major clinical applications of perfusion computed tomography are in acute stroke and in brain tumor imaging. PMID:26029020

1. Perfusion decellularization of whole organs.

PubMed

Guyette, Jacques P; Gilpin, Sarah E; Charest, Jonathan M; Tapias, Luis F; Ren, Xi; Ott, Harald C

2014-01-01

The native extracellular matrix (ECM) outlines the architecture of organs and tissues. It provides a unique niche of composition and form, which serves as a foundational scaffold that supports organ-specific cell types and enables normal organ function. Here we describe a standard process for pressure-controlled perfusion decellularization of whole organs for generating acellular 3D scaffolds with preserved ECM protein content, architecture and perfusable vascular conduits. By applying antegrade perfusion of detergents and subsequent washes to arterial vasculature at low physiological pressures, successful decellularization of complex organs (i.e., hearts, lungs and kidneys) can be performed. By using appropriate modifications, pressure-controlled perfusion decellularization can be achieved in small-animal experimental models (rat organs, 4-5 d) and scaled to clinically relevant models (porcine and human organs, 12-14 d). Combining the unique structural and biochemical properties of native acellular scaffolds with subsequent recellularization techniques offers a novel platform for organ engineering and regeneration, for experimentation ex vivo and potential clinical application in vivo.

2. In vitro perfusion of engineered heart tissue through endothelialized channels.

PubMed

Vollert, Ingra; Seiffert, Moritz; Bachmair, Johanna; Sander, Merle; Eder, Alexandra; Conradi, Lenard; Vogelsang, Alexander; Schulze, Thomas; Uebeler, June; Holnthoner, Wolfgang; Redl, Heinz; Reichenspurner, Hermann; Hansen, Arne; Eschenhagen, Thomas

2014-02-01

In engineered heart tissues (EHT), oxygen and nutrient supply via mere diffusion is a likely factor limiting the thickness of cardiac muscle strands. Here, we report on a novel method to in vitro perfuse EHT through tubular channels. Adapting our previously published protocols, we expanded a miniaturized fibrin-based EHT-format to a larger six-well format with six flexible silicone posts holding each EHT (15×25×3 mm³). Thin dry alginate fibers (17×0.04×0.04 mm) were embedded into the cell-fibrin-thrombin mix and, after fibrin polymerization, dissolved by incubation in alginate lyase or sodium citrate. Oxygen concentrations were measured with a microsensor in 14-day-old EHTs (37°C, 21% oxygen) and ranged between 9% at the edges and 2% in the center of the tissue. Perfusion rapidly increased it to 10%-12% in the immediate vicinity of the microchannel. Continuous perfusion (20 μL/h, for 3 weeks) of the tubular lumina (100-500 μm) via hollow posts of the silicone rack increased mean dystrophin-positive cardiomyocyte density (36%±6% vs. 10%±3% of total cell number) and cross sectional area (73±2 vs. 48±1 μm²) in the central part of the tissue compared to nonperfused EHTs. The channels were populated by endothelial cells present in the reconstitution cell mix. In conclusion, we developed a novel approach to generate small tubular structures suitable for perfusion of spontaneously contracting and force-generating EHTs and showed that prolonged perfusion improved cardiac tissue structure.

3. Transplacental transfer of nitrosodimethylamine in perfused human placenta.

PubMed

Annola, K; Heikkinen, A T; Partanen, H; Woodhouse, H; Segerbäck, D; Vähäkangas, K

2009-03-01

Nitrosodimethylamine (NDMA) is a carcinogenic compound present in tobacco smoke and food such as cured meat, smoked fish and beer. The O(6)-methylguanine formed in human cord blood in mothers highly exposed to such products implicates NDMA exposure of the fetus. Dual recirculating human placental perfusion was used to get direct evidence of the transplacental transfer of NDMA and DNA adduct formation in perfused human placenta. Eleven placentas from normal full-term pregnancies were collected immediately after delivery and an isolated lobule was perfused with 1 or 5 microM of (14)C-NDMA with a reference substance, antipyrine (0.1mg/ml) added to the maternal circulation. Perfusate samples were collected from both maternal and fetal circulations every half an hour for the first two hours and once per hour from thereon. NDMA was analyzed by scintillation counting and antipyrine by high performance liquid chromatography. The transfer of NDMA was comparable to that of antipyrine and probably occurred through passive diffusion, with the concentrations in maternal and fetal sides equilibrating in 2-3h. No indication of any effect by efflux transporters on NDMA kinetics was noticed in the experiments utilizing Caco-2 or MDCK- MDCKII-MDR1 cell culture monolayer in a transwell system, either. Furthermore, no NDMA-DNA-adducts were found after the perfusions and no DNA-binding of NDMA was seen in in vitro incubations with human placental microsomes from 8 additional placentas. Thus, our study demonstrates that the human fetus can be exposed to NDMA from the maternal circulation. According to this study and the literature, NDMA is not metabolized in full-term human placenta from healthy non-smoking, non-drinking mothers. It remains to be studied whether NDMA concentrations high enough to evoke fetal toxicity can be obtained from dietary sources.

4. Delusional Confusion of Dreaming and Reality in Narcolepsy

PubMed Central

Wamsley, Erin; Donjacour, Claire E.H.M.; Scammell, Thomas E.; Lammers, Gert Jan; Stickgold, Robert

2014-01-01

Study Objectives: We investigated a generally unappreciated feature of the sleep disorder narcolepsy, in which patients mistake the memory of a dream for a real experience and form sustained delusions about significant events. Design: We interviewed patients with narcolepsy and healthy controls to establish the prevalence of this complaint and identify its predictors. Setting: Academic medical centers in Boston, Massachusetts and Leiden, The Netherlands. Participants: Patients (n = 46) with a diagnosis of narcolepsy with cataplexy, and age-matched healthy healthy controls (n = 41). Interventions: N/A. Measurements and Results: “Dream delusions” were surprisingly common in narcolepsy and were often striking in their severity. As opposed to fleeting hypnagogic and hypnopompic hallucinations of the sleep/wake transition, dream delusions were false memories induced by the experience of a vivid dream, which led to false beliefs that could persist for days or weeks. Conclusions: The delusional confusion of dreamed events with reality is a prominent feature of narcolepsy, and suggests the possibility of source memory deficits in this disorder that have not yet been fully characterized. Citation: Wamsley E; Donjacour CE; Scammell TE; Lammers GJ; Stickgold R. Delusional confusion of dreaming and reality in narcolepsy. SLEEP 2014;37(2):419-422. PMID:24501437

5. Countering Climate Confusion in the Classroom: New Methods and Initiatives

McCaffrey, M.; Berbeco, M.; Reid, A. H.

2014-12-01

Politicians and ideologues blocking climate education through legislative manipulation. Free marketeers promoting the teaching of doubt and controversy to head off regulation. Education standards and curricula that skim over, omit, or misrepresent the causes, effects, risks and possible responses to climate change. Teachers who unknowingly foster confusion by presenting "both sides" of a phony scientific controversy. All of these contribute to dramatic differences in the quality and quantity of climate education received by U.S. students. Most U.S. adults and teens fail basic quizzes on energy and climate basics, in large part, because climate science has never been fully accepted as a vital component of a 21st-century science education. Often skipped or skimmed over, human contributions to climate change are sometimes taught as controversy or through debate, perpetuating a climate of confusion in many classrooms. This paper will review recent history of opposition to climate science education, and explore initial findings from a new survey of science teachers on whether, where and how climate change is being taught. It will highlight emerging effective pedagogical practices identified in McCaffrey's Climate Smart & Energy Wise, including the role of new initiatives such as the Next Generation Science Standards and Green Schools, and detail efforts of the Science League of America in countering denial and doubt so that educators can teach consistently and confidently about climate change.

6. Characterizing source confusion in HI spectral line stacking experiments

Baker, Andrew J.; Elson, Edward C.; Blyth, Sarah

2017-01-01

Forthcoming studies like the Looking At the Distant Universe with the MeerKAT Array (LADUMA) deep HI survey will rely in part on stacking experiments to detect the mean level of HI emission from populations of galaxies that are too faint to be detected individually. Preparations for such experiments benefit from the use of synthetic data cubes built from mock galaxy catalogs and containing model galaxies with realistic spatial and spectral HI distributions over large cosmological volumes. I will present a new set of such synthetic data cubes and show the results of stacking experiments with them. Because the stacked spectra can be accurately decomposed into contributions from target and non-target galaxies, it is possible to characterize the large fractions of contaminant mass that are included in stacked totals due to source confusion. Consistent with estimates extrapolated from z = 0 observational data, we find that the amount of confused mass in a stacked spectrum grows almost linearly with the size of the observational beam, suggesting potential overestimates of the cosmic neutral gas density by some recent HI stacking experiments.

7. A Spinozan lens onto the confusions of borderline relations.

PubMed

Clark, Giles

2006-02-01

In this paper the author describes how, in his analytic work with difficult personality disorders, he uses a neo-Spinozan position or attitude of alpha-thinking and functioning to understand, clarify, and so to manage confused and confusing psychosomatic 'body-mind' and emotional relations, both internally and inter-personally. Two case examples are given, followed by reflections on technique and on the limits of mourning, transformation and irony. The author suggests that a private, ideational double-aspect, mind-body position may be helpful in working with these analysands. This analytic mode may create a radically different understanding by incorporating a relational system of containment, self-containment, observation and memory. In addition, the author gives his own version of the aetiology and dynamics of borderline states and relations, and weaves the two cases he reports on into reflections on his countertransferential responses, reactions, inter-actions and 'reverie' through the lens of a neo-Spinozan conceptual system.

8. Phoneme recognition and confusions with multichannel cochlear implants: consonants.

PubMed

Välimaa, Taina T; Määttä, Taisto K; Löppönen, Heikki J; Sorri, Martti J

2002-10-01

The aim of this study was to investigate how postlingually severely or profoundly hearing-impaired adults relearn to recognize consonants after receiving multichannel cochlear implants. Consonant recognition of 19 Finnish-speaking subjects was studied for a minimum of 6 months and a maximum of 24 months using an open-set nonsense-syllable test in a prospective repeated-measure design. Responses were coded for phoneme errors, and proportions of correct responses and 95% confidence intervals were calculated for recognition and confusions. Two years after the switch-on, the mean recognition of consonants was 71% (95% confidence interval = 68-73%). The manner of articulation was easier to classify than the place of articulation, and the consonants [s], [r], [k], [t], [p], [n], and [j] were easier to recognize than [h], [m], [l], and [v]. Adaptation to electrical hearing with a multichannel cochlear implant was successful, but consonants with alveolar, palatal, or velar transitions (high F2) were better recognized than consonants with labial transitions (low F2). The locus of the F2 transitions of the consonants with better recognition was at the frequencies 1.5-2 kHz, whereas the locus of the F2 transitions of the consonants with poorer recognition was at 1.2-1.4 kHz. A tendency to confuse consonants with the closest consonant with higher F2 transition was also noted.

9. Phoneme recognition and confusions with multichannel cochlear implants: vowels.

PubMed

Välimaa, Taina T; Määttä, Taisto K; Löppönen, Heikki J; Sorri, Martti J

2002-10-01

The aim of this study was to investigate how postlingually severely or profoundly hearing-impaired adults relearn to recognize vowels after receiving multichannel cochlear implants. Vowel recognition of 19 Finnish-speaking subjects was studied for a minimum of 6 months and a maximum of 24 months using an open-set nonsense-syllable test in a prospective repeated-measure design. The responses were coded for phoneme errors, and 95% confidence intervals for recognition and confusions were calculated. The average vowel recognition was 68% (95% confidence interval = 66-70%) 6 months after switch-on and 80% (95% confidence interval = 78-82%) 24 months after switch-on. The vowels [ae], [u], [i], [o], and [a] were the easiest to recognize, and the vowels [y], [e], and [ø] were the most difficult. In conclusion, adaptation to electrical hearing using a multichannel cochlear implant was achieved well; but for at least 2 years, given two vowels with either F1 or F2 at roughly the some frequencies, confusions were drawn more towards the closest vowel with the next highest F1 or F2.

10. Dilemmas, Confusion, and Misconceptions Related to Small Airways Directed Therapy.

PubMed

Lavorini, Federico; Pedersen, Søren; Usmani, Omar S

2017-06-01

11. Procedure for decellularization of porcine heart by retrograde coronary perfusion.

PubMed

Remlinger, Nathaniel T; Wearden, Peter D; Gilbert, Thomas W

2012-12-06

Perfusion-based whole organ decellularization has recently gained interest in the field of tissue engineering as a means to create site-specific extracellular matrix scaffolds, while largely preserving the native architecture of the scaffold. To date, this approach has been utilized in a variety of organ systems, including the heart, lung, and liver (1-5). Previous decellularization methods for tissues without an easily accessible vascular network have relied upon prolonged exposure of tissue to solutions of detergents, acids, or enzymatic treatments as a means to remove the cellular and nuclear components from the surrounding extracellular environment(6-8). However, the effectiveness of these methods hinged upon the ability of the solutions to permeate the tissue via diffusion. In contrast, perfusion of organs through the natural vascular system effectively reduced the diffusion distance and facilitated transport of decellularization agents into the tissue and cellular components out of the tissue. Herein, we describe a method to fully decellularize an intact porcine heart through coronary retrograde perfusion. The protocol yielded a fully decellularized cardiac extracellular matrix (c-ECM) scaffold with the three-dimensional structure of the heart intact. Our method used a series of enzymes, detergents, and acids coupled with hypertonic and hypotonic rinses to aid in the lysis and removal of cells. The protocol used a Trypsin solution to detach cells from the matrix followed by Triton X-100 and sodium deoxycholate solutions to aid in removal of cellular material. The described protocol also uses perfusion speeds of greater than 2 L/min for extended periods of time. The high flow rate, coupled with solution changes allowed transport of agents to the tissue without contamination of cellular debris and ensured effective rinsing of the tissue. The described method removed all nuclear material from native porcine cardiac tissue, creating a site-specific cardiac ECM

12. Thallium-201 myocardial perfusion imaging in myocarditis

SciTech Connect

Tamaki, N.; Yonekura, Y.; Kadota, K.; Kambara, H.; Torizuka, K.

1985-08-01

TI-201 myocardial perfusion imaging was performed in six patients with clinically documented myocarditis. Each case manifested electrocardiographic abnormalities with elevation of serum cardiac enzymes and no significant stenosis of the coronary arteries observed on angiogram. Resting TI-201 images were visually assessed by three observers. Focal perfusion defects were observed in three cases (50%), among which two showed multiple perfusion defects. Emission computed tomography using TI-201 clearly delineated multifocal lesions in the first case. On the other hand, no significant perfusion defects were noted in the remaining three cases. Thus, myocarditis should be considered as one of the disease entities that may produce perfusion defects on TI-201 myocardial imaging.

13. Perfusion studies in cholera: methods and procedures.

PubMed

van Loon, F P; Gyr, K; Banik, A K

1992-09-01

This paper reviews the characteristics of perfusion techniques in the study of intestinal functions by specifically examining the methods and procedures of perfusion in patients with diarrhoea due to infection with V. cholerae 01. Because of abundant jejunal secretion of water and electrolytes in cholera, perfusion studies require special approaches with regard to patient preparation, use of tubing material, selection of markers, and rate of perfusion. A discussion on specific problems involved in marker perfusion techniques in cholera and on the interpretation of the results is followed by practical recommendations.

14. Mental confusion associated with scopolamine patch in elderly with mild cognitive impairment (MCI).

PubMed

Seo, Sang Won; Suh, Mee Kyung; Chin, Juhee; Na, Duk L

2009-01-01

Mental confusion or delirium can occur after application of scopolamine patch. However, predisposing factors for scopolamine-induced delirium are not known. It is expected that undetected incipient dementia or mild cognitive impairment (MCI) may be prone to develop mental confusion after applying the scopolamine patch. For the past 5 years, we found seven elderly women who had experienced transdermal scopolamine-induced mental confusion. They underwent neuropsychological tests after recovery from mental confusion (mean duration from onset to the test: 66 days). The results showed that all the patients were impaired in at least one of cognitive domains, fulfilling the criteria of MCI. These findings suggest that scopolamine patch-induced mental confusion should be included in the differential diagnoses of mental confusion in elderly, especially in travel situation, and that older people with undetected MCI are prone to develop scopolamine patch-induced mental confusion.

15. Bicarbonate diffusion through mucus.

PubMed

Livingston, E H; Miller, J; Engel, E

1995-09-01

The mucus layer overlying duodenal epithelium maintains a pH gradient against high luminal acid concentrations. Despite these adverse conditions, epithelial surface pH remains close to neutrality. The exact nature of the gradient-forming barrier remains unknown. The barrier consists of mucus into which HCO3- is secreted. Quantification of the ability of HCO3- to establish and maintain the gradient depends on accurate measurement of this ion's diffusion coefficient through mucus. We describe new experimental and mathematical methods for diffusion measurement and report diffusion coefficients for HCO3- diffusion through saline, 5% mucin solutions, and rat duodenal mucus. The diffusion coefficients were 20.2 +/- 0.10, 3.02 +/- 0.31, and 1.81 +/- 0.12 x 10(-6) cm2/s, respectively. Modeling of the mucobicarbonate layer with this latter value suggests that for conditions of high luminal acid strength the neutralization of acid by HCO3- occurs just above the epithelial surface. Under these conditions the model predicts that fluid convection toward the lumen could be important in maintaining the pH gradient. In support of this hypothesis we were able to demonstrate a net luminal fluid flux of 5 microliters.min-1.cm-2 after perfusion of 0.15 N HCl in the rat duodenum.

16. 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.

17. Metallic iron for water treatment: leaving the valley of confusion

Makota, Susanne; Nde-Tchoupe, Arnaud I.; Mwakabona, Hezron T.; Tepong-Tsindé, Raoul; Noubactep, Chicgoua; Nassi, Achille; Njau, Karoli N.

2017-07-01

Researchers on metallic iron (Fe0) for environmental remediation and water treatment are walking in a valley of confusion for 25 years. This valley is characterized by the propagation of different beliefs that have resulted from a partial analysis of the Fe0/H2O system as (1) a reductive chemical reaction was considered an electrochemical one and (2) the mass balance of iron has not been really addressed. The partial analysis in turn has been undermining the scientific method while discouraging any real critical argumentation. This communication re-establishes the complex nature of the Fe0/H2O system while recalling that, finally, proper system analysis and chemical thermodynamics are the most confident ways to solve any conflicting situation in Fe0 environmental remediation.

18. Assessor or mentor? Role confusion in professional education.

PubMed

Bray, Lucy; Nettleton, Peggy

2007-11-01

This paper reports on research conducted as part of a multi-professional study involving nursing, medicine and midwifery, which aimed to investigate both mentee and mentor perceptions of the mentorship role and the context within which it is conducted. It is well recognised that mentorship plays a vital part in the support and training of healthcare professionals. Documentation published by regulatory bodies regarding the mentorship role and changes in it's implementation in practice has resulted in confusion among practitioners. This study consisted of questionnaires and semi-structured telephone interviews with both mentors and mentees, within three healthcare professions and focuses on the responses from the nursing profession. The mentors participating in the study struggled with their dual role as assessor and mentor and found conflict within this responsibility. The role of assessor was poorly recognised and the complexity of being both an assessor and a supporter/friend is discussed.

19. Visualizing confusion matrices for multidimensional signal detection correlational methods

Zhou, Yue; Wischgoll, Thomas; Blaha, Leslie M.; Smith, Ross; Vickery, Rhonda J.

2013-12-01

Advances in modeling and simulation for General Recognition Theory have produced more data than can be easily visualized using traditional techniques. In this area of psychological modeling, domain experts are struggling to find effective ways to compare large-scale simulation results. This paper describes methods that adapt the web-based D3 visualization framework combined with pre-processing tools to enable domain specialists to more easily interpret their data. The D3 framework utilizes Javascript and scalable vector graphics (SVG) to generate visualizations that can run readily within the web browser for domain specialists. Parallel coordinate plots and heat maps were developed for identification-confusion matrix data, and the results were shown to a GRT expert for an informal evaluation of their utility. There is a clear benefit to model interpretation from these visualizations when researchers need to interpret larger amounts of simulated data.

20. [Pleasure and confusion. A footnote to Freud's translations of Mill].

PubMed

Molnar, Michael

2014-01-01

In 1863 Theodor Gomperz came to England to propose to Helen Taylor Mill, step-daughter of J. S. Mill. For several months he delayed the proposal while studying transcripts of the Philodemus papyri in the Bodleian Library. There a threatening note, supposedly left on his desk, triggered an attack of paranoia. My study of this incident, initially a mere footnote, expanded into an examination of the obscure causes of this attack. The philosophical question of the nature of desire and the researcher's passion to reconstruct a fragmented classical text are related to Gomperz's unfocussed relationship with both Mill and his step-daughter, and his ensuing confusion between reality and fantasy. The incident is considered paradigmatic of the perils of scholarly research, when the desire to possess knowledge becomes entangled with transferential relationships.

1. Acute postictal confusion and violence: Two cases with unfortunate outcomes☆

PubMed Central

Grant, Arthur C.; Koziorynska, Ewa; Lushbough, Catherine; Maus, Douglas; Mortati, Katherine

2013-01-01

Patients with temporal lobe epilepsy (TLE) often have a brief postictal state characterized by confusion and disorientation. Less common postictal behaviors include wandering and violence — both reactive and spontaneous. We describe two male patients with left TLE and unusual postictal states that led to unfortunate outcomes. The first patient's postictal state included an intense urge to peregrinate, as well as reactive violence. When a frightened houseguest prevented the patient from exiting his bedroom during a postictal state, the patient climbed out the window and fell to his death. The second patient's postictal state included menacing posturing, loud exclamation of guttural sounds or profanities, clapping or smacking his hands together, and punching nearby objects. During a postictal state at home, he grabbed a bat and destroyed furnishings. After he had two seizures at work followed by his typical postictal state, he was dismissed because of his perceived threat to coworkers. PMID:25667832

2. Misled and confused? Telling the public about MMR vaccine safety

PubMed Central

Clements, C; Ratzan, S

2003-01-01

The extraordinary events surrounding the measles, mumps, and rubella (MMR) vaccine in the United Kingdom have not only placed in jeopardy the use of this triple vaccine but have also spread concern to other parts of the world. Examination of the public's worry about MMR vaccine reveals they have been exposed to a range of conflicting views resulting in the feeling of having been misled about the safety of the vaccine. There are various groups and individuals who have legitimate roles in informing the public about such subjects. But is each one behaving in an ethically responsible way? And if confidence falters, vaccine coverage dips, and an outbreak of measles, mumps, or rubella ensues, who, if anyone, will stand and say "I misled them, I confused them, this is my responsibility"? We examine the ethical issues of each group with a voice in the debate about vaccine safety. PMID:12569190

3. Nonalcoholic fatty liver disease: the concept and confusion.

PubMed

Sanal, M G

2011-12-01

Nonalcoholic fatty liver disease (NAFLD) is generally considered as a disease associated with diabetes mellitus type 2. But on a closer evaluation we realize a host of confusion associated with this from the nomenclature, diagnosis to pathogenesis. The term refers to a spectrum ranging from steatosis to steatosis with inflammation (NASH) to cirrhosis in the absence of alcohol abuse. But in fact NAFLD is a vague term for a spectrum of diseases which differ not only in the clinical presentation but also in the etiology. NAFLD is loose to incorporate so many etiologies excluding alcoholism and few other "known" etiologies, presenting as fat in liver. Considering the diverse etiologies there is a need for personalized management in NAFLD, which at present is difficult. Currently fatty liver disease could be considered as an added Hepato-cardiovascular-renal and cancer risk factor rather than a specific diagnosis.

4. High levels of confusion for cholesterol awareness campaigns.

PubMed

Hall, Danika V

2008-09-15

Earlier this year, two industry-sponsored advertising campaigns for cholesterol awareness that target the general public were launched in Australia. These campaigns aimed to alert the public to the risks associated with having high cholesterol and encouraged cholesterol testing for wider groups than those specified by the National Heart Foundation. General practitioners should be aware of the potential for the two campaigns to confuse the general public as to who should be tested, and where. The campaign sponsors (Unilever Australasia and Pfizer) each have the potential to benefit by increased market share for their products, and increased profits. These disease awareness campaigns are examples of what is increasingly being termed "condition branding" by pharmaceutical marketing experts.

5. Hepatitis C: are you confused?: Issues related to patient education.

PubMed

Kerbleski, Marian

2005-01-01

More than 4 million Americans are infected with the hepatitis C virus. Although overshadowed by acquired immune deficiency syndrome, the hepatitis C epidemic is now recognized as a major health problem. Prevalence is estimated to be anywhere from 1.2% to 10% in specific populations. Nurses continue to express confusion in understanding the disease process; therefore, many opportunities are missed to counsel patients and families who may be at risk or who have hepatitis C. Many patient questions go unanswered because nurses mistakenly assume the medical provider will educate these patients and families. However, nurses have more contact with patients, and one of the nurse's roles is to provide health education. The Society of Gastroenterology Nurses and Associates and the Joint Commission on Accreditation of Healthcare Organizations agree it is the nurse's role to educate patients. Accurate hepatitis C virus information helps nurses guide patients and families in understanding this disease process.

6. States of confusion: Jurisdictional variation in Australian medicines nomenclature.

PubMed

Hope, Denise; King, Michelle

2015-06-01

In December 2000, the Galbally Review recommended Australia achieve national uniformity in drugs and poisons legislation. While the Commonwealth Poisons Standard classifies and schedules medicines and poisons, the Australian States and Territories are responsible for regulating the supply of medicines and poisons through individual medicines legislation. In December 2013, this legislation was examined to identify the nomenclature used to describe medicines. The research found considerable variation across jurisdictions in terms of the nomenclature used, in particular the terms used for Schedules in the State and Territory legislation were often inconsistent with each other and the terms used in the Poisons Standard. Of most concern is that the same term may be used to describe different medicines in different jurisdictions, leading to possible confusion for health practitioners working across jurisdictions as is now possible under national registration. It is therefore imperative that national uniformity of drugs and poisons legislation is achieved to facilitate a common practice reference.

7. Psychiatric diagnoses are not mental processes: Wittgenstein on conceptual confusion.

PubMed

Rosenman, Stephen; Nasti, Julian

2012-11-01

Empirical explanation and treatment repeatedly fail for psychiatric diagnoses. Diagnosis is mired in conceptual confusion that is illuminated by Ludwig Wittgenstein's later critique of philosophy (Philosophical Investigations). This paper examines conceptual confusions in the foundation of psychiatric diagnosis from some of Wittgenstein's important critical viewpoints. Diagnostic terms are words whose meanings are given by usages not definitions. Diagnoses, by Wittgenstein's analogy with 'games', have various and evolving usages that are connected by family relationships, and no essence or core phenomenon connects them. Their usages will change according to the demands and contexts in which they are employed. Diagnoses, like many psychological terms, such as 'reading' or 'understanding', are concepts that refer not to fixed behavioural or mental states but to complex apprehensions of the relationship of a variety of behavioural phenomena with the world. A diagnosis is a sort of concept that cannot be located in or explained by a mental process. A diagnosis is an exercise in language and its usage changes according to the context and the needs it addresses. Diagnoses have important uses but they are irreducibly heterogeneous and cannot be identified with or connected to particular mental processes or even with a unity of phenomena that can be addressed empirically. This makes understandable not only the repeated failure of empirical science to replicate or illuminate genetic, neurophysiologic, psychic or social processes underlying diagnoses but also the emptiness of a succession of explanatory theories and treatment effects that cannot be repeated or stubbornly regress to the mean. Attempts to fix the meanings of diagnoses to allow empirical explanation will and should fail as there is no foundation on which a fixed meaning can be built and it can only be done at the cost of the relevance and usefulness of diagnosis.

8. Adolescents Confusion in Receiving Health Services: A Qualitative Study

PubMed Central

Azh, Nezal; Ozgoli, Giti; Ardalan, Gelayol

2017-01-01

9. Intestinal perfusion monitoring using photoplethysmography

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.

10. Hyperspectral imaging for early detection of oxygenation and perfusion changes in irradiated skin

Chin, Michael S.; Freniere, Brian B.; Lo, Yuan-Chyuan; Saleeby, Jonathan H.; Baker, Stephen P.; Strom, Heather M.; Ignotz, Ronald A.; Lalikos, Janice F.; Fitzgerald, Thomas J.

2012-02-01

Studies examining acute oxygenation and perfusion changes in irradiated skin are limited. Hyperspectral imaging (HSI), a method of wide-field, diffuse reflectance spectroscopy, provides noninvasive, quantified measurements of cutaneous oxygenation and perfusion. This study examines whether HSI can assess acute changes in oxygenation and perfusion following irradiation. Skin on both flanks of nude mice (n=20) was exposed to 50 Gy of beta radiation from a strontium-90 source. Hyperspectral images were obtained before irradiation and on selected days for three weeks. Skin reaction assessment was performed concurrently with HSI. Desquamative injury formed in all irradiated areas. Skin reactions were first seen on day 7, with peak formation on day 14, and resolution beginning by day 21. HSI demonstrated increased tissue oxygenation on day 1 before cutaneous changes were observed (p<0.001). Further increases over baseline were seen on day 14, but returned to baseline levels by day 21. For perfusion, similar increases were seen on days 1 and 14. Unlike tissue oxygenation, perfusion was decreased below baseline on day 21 (p<0.002). HSI allows for complete visualization and quantification of tissue oxygenation and perfusion changes in irradiated skin, and may also allow prediction of acute skin reactions based on early changes seen after irradiation.

11. Perfusion Angiography of the Foot in Patients with Critical Limb Ischemia: Description of the Technique

SciTech Connect

Jens, Sjoerd Marquering, Henk A.; Koelemay, Mark J. W.; Reekers, Jim A.

2015-02-15

ObjectiveTo study the feasibility of 2D perfusion imaging in critical limb ischemia (CLI).Methods/ResultsPerfusion angiography is a new technology which was tested in 18 patients with CLI of the foot. A standardized protocol was used with a catheter placed at the mid-part of the popliteal artery, and a total of 9 cc of non-ionic iodinated contrast material was injected at a rate of 3 cc/sec. The technology is based on early cardiology research where iodinated contrast agents were used for imaging of cardiac perfusion. During the first pass of the contrast, there is a significant diffusion of the contrast agents into the interstitial space, particularly for non-ionic and low-molecular-weight compounds.DiscussionThe original angiography data can be used to make a time–density curve, which represents the actual perfusion of the foot in time. Angiographic perfusion imaging is a post-processing modality for which no extra contrast or radiation is needed. With this technique, it is possible to get more information about the perfusion status and microcirculation of the foot. This is a step toward functional imaging in CLI patients.

12. Hyperspectral imaging for early detection of oxygenation and perfusion changes in irradiated skin.

PubMed

Chin, Michael S; Freniere, Brian B; Lo, Yuan-Chyuan; Saleeby, Jonathan H; Baker, Stephen P; Strom, Heather M; Ignotz, Ronald A; Lalikos, Janice F; Fitzgerald, Thomas J

2012-02-01

Studies examining acute oxygenation and perfusion changes in irradiated skin are limited. Hyperspectral imaging (HSI), a method of wide-field, diffuse reflectance spectroscopy, provides noninvasive, quantified measurements of cutaneous oxygenation and perfusion. This study examines whether HSI can assess acute changes in oxygenation and perfusion following irradiation. Skin on both flanks of nude mice (n=20) was exposed to 50 Gy of beta radiation from a strontium-90 source. Hyperspectral images were obtained before irradiation and on selected days for three weeks. Skin reaction assessment was performed concurrently with HSI. Desquamative injury formed in all irradiated areas. Skin reactions were first seen on day 7, with peak formation on day 14, and resolution beginning by day 21. HSI demonstrated increased tissue oxygenation on day 1 before cutaneous changes were observed (p<0.001). Further increases over baseline were seen on day 14, but returned to baseline levels by day 21. For perfusion, similar increases were seen on days 1 and 14. Unlike tissue oxygenation, perfusion was decreased below baseline on day 21 (p<0.002). HSI allows for complete visualization and quantification of tissue oxygenation and perfusion changes in irradiated skin, and may also allow prediction of acute skin reactions based on early changes seen after irradiation.

13. Quantitative pixelwise myocardial perfusion maps from first-pass perfusion MRI.

PubMed

Weng, A M; Ritter, C O; Beer, M; Hahn, D; Köstler, H

2014-07-01

To calculate and evaluate absolute quantitative myocardial perfusion maps from rest first-pass perfusion MRI. 10 patients after revascularization of myocardial infarction underwent cardiac rest first-pass perfusion MRI. Additionally, perfusion examinations were performed in 12 healthy volunteers. Quantitative myocardial perfusion maps were calculated by using a deconvolution technique, and results were compared were the findings of a sector-based quantification. Maps were typically calculated within 3 min per slice. For the volunteers, myocardial blood flow values of the maps were 0.51 ± 0.16 ml g(-1) per minute, whereas sector-based evaluation delivered 0.52 ± 0.15 ml g(-1) per minute. A t-test revealed no statistical difference between the two sets of values. For the patients, all perfusion defects visually detected in the dynamic perfusion series could be correctly reproduced in the maps. Calculation of quantitative perfusion maps from myocardial perfusion MRI examinations is feasible. The absolute quantitative maps provide additional information on the transmurality of perfusion defects compared with the visual evaluation of the perfusion series and offer a convenient way to present perfusion MRI findings. Voxelwise analysis of myocardial perfusion helps clinicians to assess the degree of tissue damage, and the resulting maps are a good tool to present findings to patients.

14. Large enhancement of perfusion contribution on fMRI signal

PubMed Central

Wang, Xiao; Zhu, Xiao-Hong; Zhang, Yi; Chen, Wei

2012-01-01

The perfusion contribution to the total functional magnetic resonance imaging (fMRI) signal was investigated using a rat model with mild hypercapnia at 9.4 T, and human subjects with visual stimulation at 4 T. It was found that the total fMRI signal change could be approximated as a linear superposition of ‘true' blood oxygenation level-dependent (BOLD; T2/T2*) effect and the blood flow-related (T1) effect. The latter effect was significantly enhanced by using short repetition time and large radiofrequency pulse flip angle and became comparable to the ‘true' BOLD signal in response to a mild hypercapnia in the rat brain, resulting in an improved contrast-to-noise ratio (CNR). Bipolar diffusion gradients suppressed the intravascular signals but had no significant effect on the flow-related signal. Similar results of enhanced fMRI signal were observed in the human study. The overall results suggest that the observed flow-related signal enhancement is likely originated from perfusion, and this enhancement can improve CNR and the spatial specificity for mapping brain activity and physiology changes. The nature of mixed BOLD and perfusion-related contributions in the total fMRI signal also has implication on BOLD quantification, in particular, the BOLD calibration model commonly used to estimate the change of cerebral metabolic rate of oxygen. PMID:22395206

15. Ventilation-perfusion matching during exercise

NASA Technical Reports Server (NTRS)

Wagner, P. D.

1992-01-01

In normal subjects, exercise widens the alveolar-arterial PO2 difference (P[A-a]O2) despite a more uniform topographic distribution of ventilation-perfusion (VA/Q) ratios. While part of the increase in P(A-a)O2 (especially during heavy exercise) is due to diffusion limitation, a considerable amount is caused by an increase in VA/Q mismatch as detected by the multiple inert gas elimination technique. Why this occurs is unknown, but circumstantial evidence suggests it may be related to interstitial pulmonary edema rather than to factors dependent on ventilation, airway gas mixing, airway muscle tone, or pulmonary vascular tone. In patients with lung disease, the gas exchange consequences of exercise are variable. Thus, arterial PO2 may increase, remain the same, or fall. In general, patients with advanced chronic obstructive pulmonary disease (COPD) or interstitial fibrosis who exercise show a fall in PO2. This is usually not due to worsening VA/Q relationships but mostly to the well-known fall in mixed venous PO2, which itself results from a relatively smaller increase in cardiac output than VO2. However, in interstitial fibrosis (but not COPD), there is good evidence that a part of the fall in PO2 on exercise is caused by alveolar-capillary diffusion limitation of O2 transport; in COPD (but not interstitial fibrosis), a frequent additional contributing factor to the hypoxemia of exercise is an inadequate ventilatory response, such that minute ventilation does not rise as much as does CO2 production or O2 uptake, causing arterial PCO2 to increase and PO2 to fall.

16. Ventilation-perfusion matching during exercise

NASA Technical Reports Server (NTRS)

Wagner, P. D.

1992-01-01

In normal subjects, exercise widens the alveolar-arterial PO2 difference (P[A-a]O2) despite a more uniform topographic distribution of ventilation-perfusion (VA/Q) ratios. While part of the increase in P(A-a)O2 (especially during heavy exercise) is due to diffusion limitation, a considerable amount is caused by an increase in VA/Q mismatch as detected by the multiple inert gas elimination technique. Why this occurs is unknown, but circumstantial evidence suggests it may be related to interstitial pulmonary edema rather than to factors dependent on ventilation, airway gas mixing, airway muscle tone, or pulmonary vascular tone. In patients with lung disease, the gas exchange consequences of exercise are variable. Thus, arterial PO2 may increase, remain the same, or fall. In general, patients with advanced chronic obstructive pulmonary disease (COPD) or interstitial fibrosis who exercise show a fall in PO2. This is usually not due to worsening VA/Q relationships but mostly to the well-known fall in mixed venous PO2, which itself results from a relatively smaller increase in cardiac output than VO2. However, in interstitial fibrosis (but not COPD), there is good evidence that a part of the fall in PO2 on exercise is caused by alveolar-capillary diffusion limitation of O2 transport; in COPD (but not interstitial fibrosis), a frequent additional contributing factor to the hypoxemia of exercise is an inadequate ventilatory response, such that minute ventilation does not rise as much as does CO2 production or O2 uptake, causing arterial PCO2 to increase and PO2 to fall.

17. Ultrasound perfusion signal processing for tumor detection

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.

18. [Direct identification of Celosia argentea from its confused species by FTIR].

PubMed

Cheng, Cungui; Lü, Hongfei; Li, Binglan; Chen, Zongliang

2003-02-01

To directly and accurately identify Celosia argentea L. from its confused species. Fourier Transform Infrared Spectrum. Obvious characteristics for the identification in FTIR were revealed, which can be used to identify Celosia argentea L. and its confused species, such as Celosia cristata L., Amoranthus retroflexus. A. tricolor L. and A. patulus Bertol. Celosia argentea L. and its confused species were identified by FTIR directly, fastly and accurately.

19. Chromium absorption in the vascularly perfused rat intestine

SciTech Connect

Dowling, H.J.; Offenbacher, E.G.; Pi-Sunyer, F.X.

1986-03-01

The mechanism of chromium (Cr) absorption by the rat small intestine was investigated using a double perfusion technique wherein the luman of the small intestine and the vasculature supplying it were separately perfused. The intestinal perfusate (IP) was a nutrient-rich tissue culture medium (TCM) with added inorganic Cr and /sup 51/Cr. The vascular perfusate (VP) was a Krebs-Ringer bicarbonate solution (KRB) containing 4.7% dextran, 0.1% glucose and 5% human serum. Cr absorption was calculated by the amount of /sup 51/Cr detected in the VP. To determine the transport mechanism for Cr, its absorption into the VP was measured at various Cr concentrations of the IP ranging from 10-400 ppb CrCl/sub 3/. The amount of Cr absorbed into the blood rose linearly with the intestinal Cr concentration suggesting a process of simple diffusion. Manipulations of the VP and IP constituents were made to investigate their effects on Cr absorption. When serum was omitted from the VP, Cr adsorption was suppressed, suggesting that serum component(s) are necessary for optimal Cr absorption. When either of 2 plasma transport proteins (apo-transferrin, albumin) were added to the serum-free VP at physiological levels, Cr absorption returned to, but did not exceed, control levels. When the TCM was replaced with a KRB solution; Cr absorption was suppressed indicating that there are nutrient(s) of the TCM which facilitate Cr absorption. Further suppression occurred when a Cr concentration gradient opposing Cr absorption was created (IP at 100 ppb Cr, VP at 400 ppb Cr).

20. 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.

1. [Triexponential diffusion analysis in invasive ductal carcinoma and fibroadenoma].

PubMed

Nakagawa, Masayuki; Miyati, Tosiaki; Hayashi, Tatsuya; Kanao, Syotaro; Taniguchi, Masahiro; Higashimura, Kyoji; Toi, Masakazu; Togashi, Kaori

2014-03-01

To simultaneously obtain information on diffusion and perfusion in breast lesions by diffusion-weighted magnetic resonance imaging (DWI), we analyzed three diffusion components using a triexponential function. Eighteen subjects [10 with invasive ductal carcinoma (IDC), 8 with fibroadenoma] were evaluated using DWI with multiple b-values. We derived perfusion-related diffusion, fast free diffusion, and slow restricted diffusion coefficients (Dp, Df, Ds) calculated from the triexponential function using the DWI data. Moreover, the triexponential analysis was compared with biexponential and monoexponential analyses. Each diffusion coefficient with a triexponential function was correlated to a relative enhancement ratio (RER) using dynamic contrast-enhanced MRI. In triexponential analysis, Dp and Ds in IDC were significantly higher than those for fibroadenoma. There was no correlation between each diffusion coefficient from the triexponential analysis in any of the groups (Dp, Df, and Ds), but biexponential analysis revealed a positive correlation between each diffusion coefficient in breast lesions. Strong correlations were found between Dp and RERs. Triexponential analysis thus makes it possible to obtain, in noninvasive fashion, more detailed diffusion and perfusion information in breast lesions.

2. Coherence, competence, and confusion in narratives of middle childhood.

PubMed

Weinstein, Lissa; Shustorovich, Ellen

2011-01-01

Middle childhood is a pivotal time in character development during which enduring internal structures are formed. Fiction can offer insights into the cognitive and affective shifts of this developmental phase and how they are transformed in adulthood. While the success of beloved books for latency age children lies in the solutions they offer to the conflict between the pull toward independence and the pull back to the safety of childhood, the enduring stories for adults about children in their middle years can be seen as works of mourning for the relationship with the parents and the childhood self, but more importantly as attempts to transform their experience of middle childhood through the retrospective creation of a coherence that was initially absent. Thematic and structural elements distinguish two groups of stories for adults: the first appears to solve the conflicts of this period by importing adult knowledge and perspective into the narrative of childhood; the second describes the unconscious disorganizing aspects of this period, thereby offering readers a chance to reorganize their own memories, to make a coherent whole out of the fragmented, the confusing, and the unresolved.

3. Toward less confusing terminology in endocrine disruptor research.

PubMed

Foster, Warren G; Agzarian, John

2008-03-01

The realization that environmental contaminants interact with hormone receptors and mimic or antagonize the actions of endogenous hormones led to introduction of terms such as endocrine disruptor, endocrine disrupter, hormonally active chemicals, and hormone mimics into the scientific and lay press. Reports suggesting a link between exposure to chemicals adversely affecting the endocrine system and (1) increasing rates of hormone-dependent cancers (breast, prostate, and testicular), (2) developmental detrimental effects in the male reproductive tract, (3) falling sperm counts, and (4) endometriosis resulted in an explosion of research, regulatory actions, and policy changes aimed at better understanding the hazards posed by these chemicals with subsequent restriction in their use. With increasing concern, there is worldwide action to develop testing strategies to allow for early identification of chemicals possessing endocrine disruptor activity. However, despite an expanding literature and numerous expert panel meetings, there continues to be controversy surrounding how to best define endocrine disruptors, resulting in (1) ambiguous use of the term, (2) confusion in the literature, and (3) publication of contentious lists of chemicals purported to be endocrine disruptors. Herein it is argued in favor of a more restrictive definition with adoption of a less ambiguous term, and in favor of development of a classification system to enhance more effective communication and facilitate appropriate allocation of limited resources in this highly charged area of toxicology.

4. PRP in OA knee - update, current confusions and future options.

PubMed

Dhillon, Mandeep S; Patel, Sandeep; John, Rakesh

2017-01-01

Positive results have been uniformly observed by various researchers for platelet-rich plasma (PRP) in early osteoarthritis (OA) knee in the past few years. PRP has clearly demonstrated its supremacy in comparison to hyaluronic acid (HA) and placebo in various clinical trials and is undoubtedly the best option available for symptomatic treatment in early OA. The release of growth factors from PRP occurs immediately and lasts for around three weeks and the clinical effect tends to wane down by the end of the year. Prolonged and sustained release of growth factors from platelets could possibly help in much better biological healing and sustained clinical effects. PRP in combination with biocompatible carriers could be one way of achieving this. Gelatin hydrogel PRP and chitosan PRP seem to be promising based on early in vitro studies and animal studies. PRP in combination with hyaluronic acid also seems to be additive. This article intends to discuss the present status of the PRP, confusions surrounding its use, upcoming trends and ideas for improvising PRP for use early OA knees based on available evidence. © The Authors, published by EDP Sciences, 2017.

5. Brand name confusion: Subjective and objective measures of orthographic similarity.

PubMed

Burt, Jennifer S; McFarlane, Kimberley A; Kelly, Sarah J; Humphreys, Michael S; Weatherall, Kimberlee; Burrell, Robert G

2017-09-01

Determining brand name similarity is vital in areas of trademark registration and brand confusion. Students rated the orthographic (spelling) similarity of word pairs (Experiments 1, 2, and 4) and brand name pairs (Experiment 5). Similarity ratings were consistently higher when words shared beginnings rather than endings, whereas shared pronunciation of the stressed vowel had small and less consistent effects on ratings. In Experiment 3 a behavioral task confirmed the similarity of shared beginnings in lexical processing. Specifically, in a task requiring participants to decide whether 2 words presented in the clear (a probe and a later target) were the same or different, a masked prime word preceding the target shortened response latencies if it shared its initial 3 letters with the target. The ratings of students for word and brand name pairs were strongly predicted by metrics of orthographic similarity from the visual word identification literature based on the number of shared letters and their relative positions. The results indicate a potential use for orthographic metrics in brand name registration and trademark law. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

6. Confusion in Direct Imaging of Earth-Clones

Pan, Xiaopei; Shao, M.; Catanzarite, J.

2010-05-01

It is an important and necessary goal to image Earth-clones and to further study atmospheres of those exoplanets. It is, however, arguable whether direct imaging can discover and characterize Earth-like planets alone, or if direct imaging definitely needs astrometric discoveries of Earth-clones first. Several proposed imaging missions for searching Earth-clones are evaluated in this work. Challenging issues in direct imaging of Earth-clones are discussed. In particular, confusing issues in direct imaging coming from background objects, distant M, T, L types of stars, faint brown dwarfs and multiple planets are investigated. Also, the impacts of zodiacal and exozodiacal dust clouds on signal-to-noise ratios of direct imaging are analyzed. There is no doubt that the best strategy to explore Earth-clones uses discoveries of Earth-clones by an astrometry mission first, which is then followed by an imaging mission to improve Earth-clones’ orbital parameters and to further characterize their physical parameters. We believe that the synergy of direct imaging of Earth-clones with astrometry is the most effective observation strategy to search for and investigate Earth-clones in the foreseeable future.

7. [Asymmetric confusability effect in recognition memory of cats pictures].

PubMed

Ando, M; Hakoda, Y

1999-06-01

Performance superiority of the addition of features in the stimuli over the deletion on recognition (asymmetric confusability effect) has been shown in previous studies (Pezdek, Maki, Valencia-Laver, Whetstone, Stoeckert, & Dougherty, 1988; Ando & Hakoda, 1998). We investigated the same effect by using a familiar living thing (cat) as a stimulus. Ten subjects were given a recognition task using pictures of cats with feature changes (additions, deletions, or no change). Results showed that the picture with deletions were easier to recognize than those with additions, which was opposite to the previous studies. Then, we examined the possibility that performance superiority of the deletions over the additions was mediated by the factor of impression. Another group of 18 subjects was asked to rate the impression scales consisting of a "typicality-reality factor", a "stability-balance factor", and a "grotesque-disgust factor". Results showed that there was a significant difference in impression ratings for each factor between the additions and the deletions, and that impression ratings predicted recognition performance well. It was concluded that performance superiority of the deletions over the additions was mediated by the factor of impression.

8. Delusional confusion of dreaming and reality in narcolepsy.

PubMed

Wamsley, Erin; Donjacour, Claire E H M; Scammell, Thomas E; Lammers, Gert Jan; Stickgold, Robert

2014-02-01

We investigated a generally unappreciated feature of the sleep disorder narcolepsy, in which patients mistake the memory of a dream for a real experience and form sustained delusions about significant events. We interviewed patients with narcolepsy and healthy controls to establish the prevalence of this complaint and identify its predictors. Academic medical centers in Boston, Massachusetts and Leiden, The Netherlands. Patients (n = 46) with a diagnosis of narcolepsy with cataplexy, and age-matched healthy healthy controls (n = 41). N/A. "Dream delusions" were surprisingly common in narcolepsy and were often striking in their severity. As opposed to fleeting hypnagogic and hypnopompic hallucinations of the sleep/wake transition, dream delusions were false memories induced by the experience of a vivid dream, which led to false beliefs that could persist for days or weeks. The delusional confusion of dreamed events with reality is a prominent feature of narcolepsy, and suggests the possibility of source memory deficits in this disorder that have not yet been fully characterized.

9. Focal Electroencephalographic Changes Index Post-Traumatic Confusion and Outcome.

PubMed

Shah, Sudhin A; Mohamadpour, Maliheh; Askin, Gulce; Nakase-Richardson, Risa; Stokic, Dobrivoje S; Sherer, Mark; Yablon, Stuart A; Schiff, Nicholas D

2017-10-01

While the duration and severity of post-traumatic confusional state (PTCS) after traumatic brain injury have well-established implications for long-term outcomes, little is known about the underlying pathophysiology and their role in functional outcomes. Here, we analyzed the delta-to-alpha frequency band power ratios (DAR) from localized scalp areas derived from standard resting electroencephalographic (EEG) data recorded during eyes closed state in 49 patients diagnosed with PTCS. Higher global, occipital, parietal, and temporal DARs were significantly associated with the severity of PTCS, as assessed by the Confusion Assessment Protocol (CAP) observed on the same day, after controlling for injury severity. Also, occipital DARs were positively associated with both the CAP disorientation score 2, and the CAP symptom fluctuation score 4, after controlling for injury severity (n = 35). Posterior DARs were significantly associated with Functional Independence Measure-cognitive subscale average score at 1 (n = 45), 2 (n = 42), and 5 (n = 34) year(s) post-injury. The associations at 1 (temporal left) and 2 (parietal left) years survive after controlling for an injury severity index. Our finding that posterior DAR is a marker of PTCS and functional recovery post-injury, likely reflects functional de-afferentation of the posterior medial complex (PMC) in PTCS. Altered function of the PMC is proposed as a unifying physiological mechanism underlying both acute and chronic confusional states. We discuss the relationship of these findings to electrophysiological markers associated with disorders of consciousness.

10. Contrast, contours and the confusion effect in dazzle camouflage

PubMed Central

Scott-Samuel, Nicholas E.; Cuthill, Innes C.

2016-01-01

‘Motion dazzle camouflage’ is the name for the putative effects of highly conspicuous, often repetitive or complex, patterns on parameters important in prey capture, such as the perception of speed, direction and identity. Research into motion dazzle camouflage is increasing our understanding of the interactions between visual tracking, the confusion effect and defensive coloration. However, there is a paucity of research into the effects of contrast on motion dazzle camouflage: is maximal contrast a prerequisite for effectiveness? If not, this has important implications for our recognition of the phenotype and understanding of the function and mechanisms of potential motion dazzle camouflage patterns. Here we tested human participants' ability to track one moving target among many identical distractors with surface patterns designed to test the influence of these factors. In line with previous evidence, we found that targets with stripes parallel to the object direction of motion were hardest to track. However, reduction in contrast did not significantly influence this result. This finding may bring into question the utility of current definitions of motion dazzle camouflage, and means that some animal patterns, such as aposematic or mimetic stripes, may have previously unrecognized multiple functions. PMID:27493775

11. NUTRITIONAL STUDIES ON THE CONFUSED FLOUR BEETLE, TRIBOLIUM CONFUSUM DUVAL

PubMed Central

Chapman, Royal N.

1924-01-01

The confused flour beetle (Tribolium confusum) was chosen for this study because it lives in a food which ordinarily contains no living organisms. The death rates are greater in cultures which are handled daily than in those which are not handled but when all are handled alike the results are comparable. The results from experiments with individual beetles in various kinds of flour were plotted with instars (larval stages) on the ordinate and time in days on the abscissa, using the results from control experiments in wheat flour to determine the length of the various instars from an "x = y" formula. The curves of development were found to be straight lines throughout all but the last instar. The curve for the last instar during which the larva transformed deviated from the straight line in certain foods, notably rice flour. When mass cultures were used the death and transformation curves were plotted for each synthetic food. A comparison of the curves from wheat flour and the synthetic foods shows that the first parts of the curves are very much alike in all cases and that a few resemble the control in every respect except that the transformation curve has been moved back for a considerable time. The death curves for the mass cultures are not smooth but show sudden increase in death at approximately the times of molting. These curves may therefore be compared with the records from individual beetles. PMID:19872096

12. Signal affects and our psychoanalytic confusion of tongues.

PubMed

Jacobson, J G

1994-01-01

Difficulties psychoanalysts of different points of view have in communicating with one another are reviewed. Reexamination of the structural theory distinguishes the tripartite theory of 1923 from the signal affect model of 1926; the latter concept is traced through the post-Freudian relational points of view. This signal affect model provides a base for what the author sees as a core commonality among the diverse current theories, as well as a basis for sharper, more empirically arguable differentiation of the divergences and incompatibilities among them. The interest in and acceptance, in recent years, of Ferenczi's contributions in his 1933 paper on confusion of tongues reflect a shift in our views of psychoanalytic technique over the intervening years, toward an interactional view of the psychoanalytic process. The relational points of view have been instrumental in this shift, by direct contributions, and indirectly by challenging and inspiring the classical viewpoint to develop and change. The relational points of view, in addition to focusing on different contents, also prescribe differences in technical approach and in the climate within which an analysis is conducted, presenting valuable alternatives in clinical work. Finally, arguments are offered in favor of clinicians using multiple theoretical points of view for access to the varied clinical tasks demanded by analytic work.

13. Miller and Nicely's confusion data are predicted by Fletcher's AI

Allen, Jont B.

2004-05-01

Starting from the confusion matrix data Pij(SNR) of Miller and Nicely, where i indexes the stimulus and j the response, the average performance intensity (PI) function, over the 16 consonants, may be defined as P(SNR)=∑i=116Pii(SNR). These data are for five female talkers. The average speech power for five female talkers is known from Dunn and White. Thus, the articulation index (AI) may be computed at each SNR value (the maximum AI value is 0.6). This allows one to re-express P(SNR) as P(AI). When the resulting function is compared to Fletcher's formula for the AI, P(AI)=1-eminAI, with emin=0.015, the agreement is nearly perfect. Thus, the Miller and Nicely average phone data may be modeled by AI theory. This result seems astounding, as it falls outside normal realm of the AI, which was intended for a much larger mix of sounds, not 16 consonants and a fixed vowel. Most individual consonant PI functions obey the same Fletcher AI formula, but with different values of emin.

14. Cases In Which Ancestral Maximum Likelihood Will Be Confusingly Misleading.

PubMed

Handelman, Tomer; Chor, Benny

2017-03-02

Ancestral maximum likelihood (AML) is a phylogenetic tree reconstruction criteria that "lies between" maximum parsimony (MP) and maximum likelihood (ML). ML has long been known to be statistically consistent. On the other hand, Felsenstein (1978) showed that MP is statistically inconsistent, and even positively misleading: There are cases where the parsimony criteria, applied to data generated according to one tree topology, will be optimized on a different tree topology. The question of weather AML is statistically consistent or not has been open for a long time. Mosel, Roch, and Steel (2009) have shown that AML can "shrink" short tree edges, resulting in a star tree with no internal resolution, which yields a better AML score than the original (resolved) model. This result implies that AML is statistically inconsistent, but not that it is positively misleading, because the star tree is compatible with any other topology. We show that AML is confusingly misleading: For some simple, four taxa (resolved) tree, the ancestral likelihood optimization criteria is maximized on an incorrect (resolved) tree topology, as well as on a star tree (both with specific edge lengths), while the tree with the original, correct topology, has strictly lower ancestral likelihood. Interestingly, the two short edges in the incorrect, resolved tree topology are of length zero, and are not adjacent, so this resolved tree is in fact a simple path. While for MP, the underlying phenomenon can be described as long edge attraction, it turns out that here we have long edge repulsion.

15. The Lost Lamb: A Literature Review on the Confusion of College Students in China

ERIC Educational Resources Information Center

Dong, Jianmei; Han, Fubin

2010-01-01

With the development of mass higher education in China, confusion--a contradictory state between college students' awareness of employment, learning, morality, and their own behavior and societal requirements--is proving a ubiquitous problem among college students. His confusion has garnered much social attention. In this paper, the origins of…

16. Eye Tracking and Early Detection of Confusion in Digital Learning Environments: Proof of Concept

ERIC Educational Resources Information Center

Pachman, Mariya; Arguel, Amaël; Lockyer, Lori; Kennedy, Gregor; Lodge, Jason M.

2016-01-01

Research on incidence of and changes in confusion during complex learning and problem-solving calls for advanced methods of confusion detection in digital learning environments (DLEs). In this study we attempt to address this issue by investigating the use of multiple measures, including psychophysiological indicators and self-ratings, to detect…

17. Predictors of Self-Reported Problems of Confusion among the Aged.

ERIC Educational Resources Information Center

Grams, Armin E.; Cutler, Stephen J.

1992-01-01

Responses to questions on 1984 Supplement on Aging to National Health Interview Survey revealed that two-thirds of interviewees reported never having episode of confusion during preceding year. For those who admitted occasional confusion, memory loss and forgetfulness emerged as single best predictors of how often respondent reported getting…

18. An Analysis of Teachers' Concept Confusion Concerning Electric and Magnetic Fields

ERIC Educational Resources Information Center

Hekkenberg, Ans; Lemmer, Miriam; Dekkers, Peter

2015-01-01

In an exploratory study, 36 South African physical science teachers' understanding of basic concepts concerning electric and magnetic fields was studied from a perspective of possible concept confusion. Concept confusion is said to occur when features of one concept are incorrectly attributed to a different concept, in the case of this study to…

19. Inside Out: Detecting Learners' Confusion to Improve Interactive Digital Learning Environments

ERIC Educational Resources Information Center

Arguel, Amaël; Lockyer, Lori; Lipp, Ottmar V.; Lodge, Jason M.; Kennedy, Gregor

2017-01-01

Confusion is an emotion that is likely to occur while learning complex information. This emotion can be beneficial to learners in that it can foster engagement, leading to deeper understanding. However, if learners fail to resolve confusion, its effect can be detrimental to learning. Such detrimental learning experiences are particularly…

20. Annual Percentage Rate and Annual Effective Rate: Resolving Confusion in Intermediate Accounting Textbooks

ERIC Educational Resources Information Center

Vicknair, David; Wright, Jeffrey

2015-01-01

Evidence of confusion in intermediate accounting textbooks regarding the annual percentage rate (APR) and annual effective rate (AER) is presented. The APR and AER are briefly discussed in the context of a note payable and correct formulas for computing each is provided. Representative examples of the types of confusion that we found is presented…

1. Mapping the literature of perfusion.

PubMed Central

Hall, E F

1999-01-01

Perfusionists select and operate the equipment necessary for monitoring, supporting, or temporarily replacing the patient's circulatory or respiratory function. There are over 3,000 perfusionists working in U.S. hospitals, medical and perfusionist groups, and as independent contractors. The purpose of this study was to identify the core literature of perfusion and to determine which major databases provide the most thorough access to this literature. This paper is part of the Medical Library Association Nursing and Allied Health Resource Section's project to map the literature of the allied health professions. It uses a bibliometric methodology to identify core journals. A group of forty-three journals was determined to make up the core journal literature of perfusion. MEDLINE provided the best overall indexing coverage for these journals, but librarians and perfusionists will wish to supplement its use with the Cumulative Index to Nursing and Allied Health Literature in order to access the journals written primarily for perfusionists. The study results can guide purchasing and database searching decisions of collection development and reference librarians, encourage the database producer to increase coverage of titles that are unindexed or underindexed, and advise perfusionists of the best access to their core literature. PMID:10427432

2. Confusion: acetaminophen dosing changes based on NO evidence in adults.

PubMed

Krenzelok, Edward P; Royal, Mike A

2012-06-01

Acetaminophen (paracetamol) plays a vital role in American health care, with in excess of 25 billion doses being used annually as a nonprescription medication. Over 200 million acetaminophen-containing prescriptions, usually in combination with an opioid, are dispensed annually. While acetaminophen is recognized as a safe and effective analgesic and antipyretic, it is also associated with significant morbidity and mortality (hepatotoxicity) if doses in excess of the therapeutic amount are ingested inappropriately. The maximum daily therapeutic dose of 3900-4000 mg was established in separate actions in 1977 and 1988, respectively, via the Food and Drug Administration (FDA) monograph process for nonprescription medications. The FDA has conducted multiple advisory committee meetings to evaluate acetaminophen and its safety profile, and has suggested (but not mandated) a reduction in the maximum daily dosage from 3900-4000 mg to 3000-3250 mg. In 2011, McNeil, the producer of the Tylenol® brand of acetaminophen, voluntarily reduced the maximum daily dose of its 500 mg tablet product to 3000 mg/day, and it has pledged to change the labeling of its 325 mg/tablet product to reflect a maximum of 3250 mg/day. Generic manufacturers have not changed their dosing regimens and they have remained consistent with the established monograph dose. Therefore, confusion will be inevitable as both consumers and health care professionals try to determine the proper therapeutic dose of acetaminophen. Which is the correct dose of acetaminophen: 3000 mg if 500 mg tablets are used, 3250 mg with 325 mg tablets, or 3900 mg when 650 mg arthritis-strength products are used?

3. Oral alprazolam acutely increases nucleus accumbens perfusion

PubMed Central

Wolf, Daniel H.; Pinkham, Amy E.; Satterthwaite, Theodore D.; Ruparel, Kosha; Elliott, Mark A.; Valdez, Jeffrey; Smith, Mark A.; Detre, John A.; Gur, Ruben C.; Gur, Raquel E.

2014-01-01

Benzodiazepines treat anxiety, but can also produce euphoric effects, contributing to abuse. Using perfusion magnetic resonance imaging, we provide the first direct evidence in humans that alprazolam (Xanax) acutely increases perfusion in the nucleus accumbens, a key reward-processing region linked to addiction. PMID:23070072

4. 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.

5. Technetium myocardial perfusion agents: an introduction

SciTech Connect

English, R.J.; Kozlowski, J.; Tumeh, S.S.; Holman, B.L.

1987-09-01

This is the third in a series of four Continuing Education articles on developing radiopharmaceuticals. After reading this article, the reader should be able to: 1) understand the basic concepts of myocardial perfusion imaging; and 2) discuss the advantages of the technetium myocardial perfusion complexes over thallium-201.

6. Luxury perfusion following anterior ischemic optic neuropathy.

PubMed

Friedland, S; Winterkorn, J M; Burde, R M

1996-09-01

We present five patients who developed luxury perfusion following anterior ischemic optic neuropathy in whom fluorescein angiography was misinterpreted as "capillary hemangioma" or neovascularization of the disc. In each case, the segment of disc hyperemia corresponded to a spared region of visual field. Luxury perfusion represents a reparative autoregulatory reaction to ischemia.

7. 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

8. Myocardial perfusion with rubidium-82. III. Theory relating severity of coronary stenosis to perfusion deficit

SciTech Connect

Mullani, N.A.

1984-11-01

The relation between the quantitative perfusion deficit, as measured by emission computerized tomography, and the severity of coronary artery stenosis is important for the noninvasive clinical evaluation of coronary artery disease in man. Positron emission tomography allows direct noninvasive measurement of myocardial perfusion and quantification of the size of the perfusion defect. Given this important imformation, a mathematical model has been derived to gauge the severity of a coronary stenosis from quantitative perfusion measurements in the normal and poststenotic regions of the heart. The theoretical basis is presented for relating regional myocardial perfusion and regional perfusion resistance to total, coronary blood flow and resistance at normal resting flow and during maximal coronary vasodilation. The concept of perfusion reserve is presented as a clinical measure of the severity of a stenosis.

9. Dependence of Brain Intravoxel Incoherent Motion Perfusion Parameters on the Cardiac Cycle

PubMed Central

Federau, Christian; Hagmann, Patric; Maeder, Philippe; Müller, Markus; Meuli, Reto; Stuber, Matthias; O’Brien, Kieran

2013-01-01

Measurement of microvascular perfusion with Intravoxel Incoherent Motion (IVIM) MRI is gaining interest. Yet, the physiological influences on the IVIM perfusion parameters (“pseudo-diffusion” coefficient D*, perfusion fraction f, and flow related parameter fD*) remain insufficiently characterized. In this article, we hypothesize that D* and fD*, which depend on blood speed, should vary during the cardiac cycle. We extended the IVIM model to include time dependence of D* = D*(t), and demonstrate in the healthy human brain that both parameters D* and fD* are significantly larger during systole than diastole, while the diffusion coefficient D and f do not vary significantly. The results non-invasively demonstrate the pulsatility of the brain’s microvasculature. PMID:24023649

10. Contrast-enhanced ultrasound: A promising method for renal microvascular perfusion evaluation.

PubMed

Wang, Ling; Mohan, Chandra

2016-09-01

This article reviews the application of contrast-enhanced ultrasound (CEUS) in gauging renal microvascular perfusion in diverse renal diseases. The unique nature of the contrast agents used in CEUS provides real-time and quantitative imaging of the vasculature. In addition to the traditional use of CEUS for evaluation of kidney masses, it also emerges as a safe and effective imaging approach to assess microvascular perfusion in diffuse renal lesions, non-invasively. Although the precise CEUS parameters that may best predict disease still warrant systematic evaluation, animal models and limited clinical trials in humans raise hopes that CEUS could outcompete competing modalities as a first-line tool for assessing renal perfusion non-invasively, even in ailments such as acute kidney injury and chronic kidney disease.

11. Contrast-enhanced ultrasound: A promising method for renal microvascular perfusion evaluation

PubMed Central

2016-01-01

Abstract This article reviews the application of contrast-enhanced ultrasound (CEUS) in gauging renal microvascular perfusion in diverse renal diseases. The unique nature of the contrast agents used in CEUS provides real-time and quantitative imaging of the vasculature. In addition to the traditional use of CEUS for evaluation of kidney masses, it also emerges as a safe and effective imaging approach to assess microvascular perfusion in diffuse renal lesions, non-invasively. Although the precise CEUS parameters that may best predict disease still warrant systematic evaluation, animal models and limited clinical trials in humans raise hopes that CEUS could outcompete competing modalities as a first-line tool for assessing renal perfusion non-invasively, even in ailments such as acute kidney injury and chronic kidney disease. PMID:28191530

12. Investigation of source-detector separation optimization for an implantable perfusion and oxygenation sensor for liver blood vessels

SciTech Connect

Baba, Justin S; Akl, Tony; Cote, Gerard L.; Wilson, Mark A.; Ericson, Milton Nance

2011-01-01

An implanted system is being developed to monitor transplanted liver health during the critical 7-10 day period posttransplantation. The unit will monitor organ perfusion and oxygen consumption using optically-based probes placed on both the inflow and outflow blood vessels, and on the liver parenchymal surface. Sensing probes are based on a 3- wavelength LED source and a photodiode detector. Sample diffuse reflectance is measured at 735, 805, and 940 nm. To ascertain optimal source-to-photodetector spacing for perfusion measurement in blood vessels, an ex vivo study was conducted. In this work, a dye mixture simulating 80% blood oxygen saturation was developed and perfused through excised porcine arteries while collecting data for various preset probe source-to-photodetector spacings. The results from this study demonstrate a decrease in the optical signal with decreasing LED drive current and a reduction in perfusion index signal with increasing probe spacing. They also reveal a 2- to 4-mm optimal range for blood vessel perfusion probe source-to-photodetector spacing that allows for sufficient perfusion signal modulation depth with maximized signal to noise ratio (SNR). These findings are currently being applied to guide electronic configuration and probe placement for in vivo liver perfusion porcine model studies.

13. Is discussion of colorectal cancer screening options associated with heightened patient confusion?

PubMed Central

Jones, Resa M.; Vernon, Sally W.; Woolf, Steven H.

2010-01-01

14. Is discussion of colorectal cancer screening options associated with heightened patient confusion?

PubMed

Jones, Resa M; Vernon, Sally W; Woolf, Steven H

2010-11-01

15. ANTONIA perfusion and stroke. A software tool for the multi-purpose analysis of MR perfusion-weighted datasets and quantitative ischemic stroke assessment.

PubMed

Forkert, N D; Cheng, B; Kemmling, A; Thomalla, G; Fiehler, J

2014-01-01

The objective of this work is to present the software tool ANTONIA, which has been developed to facilitate a quantitative analysis of perfusion-weighted MRI (PWI) datasets in general as well as the subsequent multi-parametric analysis of additional datasets for the specific purpose of acute ischemic stroke patient dataset evaluation. Three different methods for the analysis of DSC or DCE PWI datasets are currently implemented in ANTONIA, which can be case-specifically selected based on the study protocol. These methods comprise a curve fitting method as well as a deconvolution-based and deconvolution-free method integrating a previously defined arterial input function. The perfusion analysis is extended for the purpose of acute ischemic stroke analysis by additional methods that enable an automatic atlas-based selection of the arterial input function, an analysis of the perfusion-diffusion and DWI-FLAIR mismatch as well as segmentation-based volumetric analyses. For reliability evaluation, the described software tool was used by two observers for quantitative analysis of 15 datasets from acute ischemic stroke patients to extract the acute lesion core volume, FLAIR ratio, perfusion-diffusion mismatch volume with manually as well as automatically selected arterial input functions, and follow-up lesion volume. The results of this evaluation revealed that the described software tool leads to highly reproducible results for all parameters if the automatic arterial input function selection method is used. Due to the broad selection of processing methods that are available in the software tool, ANTONIA is especially helpful to support image-based perfusion and acute ischemic stroke research projects.

16. Wernicke's Encephalopathy Mimicking Acute Onset Stroke Diagnosed by CT Perfusion

PubMed Central

Advani, Rajiv; Kurz, Kathinka D.; Kurz, Martin W.

2014-01-01

Background. Metabolic syndromes such as Wernicke's encephalopathy may present with a sudden neurological deficit, thus mimicking acute onset stroke. Due to current emphasis on rapid admission and treatment of acute stroke patients, there is a significant risk that these stroke mimics may end up being treated with thrombolysis. Rigorous clinical and radiological skills are necessary to correctly identify such metabolic stroke mimics, in order to avoid doing any harm to these patients due to the unnecessary use of thrombolysis. Patient. A 51-year-old Caucasian male was admitted to our hospital with suspicion of an acute stroke due to sudden onset dysarthria and unilateral facial nerve paresis. Clinical examination revealed confusion and dysconjugate gaze. Computed tomography (CT) including a CT perfusion (CTP) scan revealed bilateral thalamic hyperperfusion. The use of both clinical and radiological findings led to correctly diagnosing Wernicke's encephalopathy. Conclusion. The application of CTP as a standard diagnostic tool in acute stroke patients can improve the detection of stroke mimics caused by metabolic syndromes as shown in our case report. PMID:24716022

17. Visual assessment of magnetic resonance imaging perfusion lesions in a large patient group.

PubMed

Siemonsen, S; Fitting, T; Thomalla, G; Krützelmann, A; Fiehler, J

2012-12-01

Few magnetic resonance imaging (MRI) studies of stroke have evaluated the value of visual assessment of perfusion/diffusion mismatch, which is crucial for routine application. In this study an attempt was made to visually assess perfusion lesions resembling the acute clinical situation and identify parameters with the highest interobserver reliability when used to define a perfusion/diffusion mismatch and the highest accuracy for prediction of infarct growth. Magnetic resonance imaging was performed within 6 h of symptom onset and again 1-11 days thereafter in 86 consecutive stroke patients who received intravenous thrombolytic therapy. The MRI protocol included diffusion-weighted imaging apparent diffusion coefficient (DWI/ADC), fluid-attenuated inversion recovery (FLAIR) and perfusion imaging (PI). Maps for different perfusion parameters, e.g. cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT) and time to peak (TTP) were calculated. Areas of perfusion deficits of all perfusion parameters were visually compared to corresponding ADCs and final infarct size by two independent observers. The final infarct size was overestimated by TTP (in 81/83 patients by raters 1 and 2, respectively), MTT (82/83) and CBF (65/74) lesions. The ADC lesions were rated smaller than the final infarct size in 43/38 cases by raters 1 and 2 and the CBV decrease was rated to underestimate final infarct size in 40/31 cases. The only significantly increased OR of 3.883 (95 % CI 1.466-10.819, p = 0.004, rater 1)/5.142 (95 % CI 1.828-15.142, p = 0.001, rater 2) for predicting infarct growth was observed for the presence of a CBV > ADC mismatch, which also showed the highest kappa value of 0.407. All mismatch patterns were prone to high interrater variability when assessed under conditions resembling the clinical setting. Of all tested mismatch patterns the CBV > ADC mismatch was the strongest predictor of lesion growth while visual assessment of TTP and CBF generally

18. Protoporphyrin-induced Cholestasis in the Isolated In Situ Perfused Rat Liver

PubMed Central

Avner, Dennis L.; Lee, Randall G.; Berenson, Malcolm M.

1981-01-01

The pathogenesis of liver disease in protoporphyria has been presumed to result from the hepatic deposition of protoporphyrin. To examine the effects of protoporphyrin on hepatic bile flow and histopathology, studies were performed employing an isolated, in situ, rat liver perfusion system. Rat livers in the control group were perfused with 0-80 μmol sodium taurocholate/h. Rat livers in the experimental group were perfused with sodium taurocholate and (a) sufficient quantities of protoporphyrin to produce maximal canalicular secretion and (b) perfusate protoporphyrin concentrations of 0.01, 0.1, and 1 μM. The administration of protoporphyrin sufficient to achieve maximal canalicular secretion was found to significantly reduce bile flow in rats infused with 0, 40, and 80 μmol sodium taurocholate/h. Linear regression analysis defined the relationship between bile flow and biliary bile acid secretion and showed that the bile acid-independent fraction of bile flow was reduced (P < 0.01). Bile acid-dependent flow was unaffected and there was no significant difference in biliary bile acid secretion rates between control and protoporphyrin-perfused livers. Perfusion of rat livers with varying concentrations of protoporphyrin demonstrated the reduction of bile flow was dose-related. Analysis of perfusate enzyme activity did not reveal abnormalities that could account for the cholestasis. Studies to evaluate the effect of protoporphyrin on regional hepatic hemodynamics were inconclusive. Histopathological studies of control and protoporphyrin-perfused rat livers did not show abnormalities on light microscopy. However, canalicular dilatation, distortion, and loss of microvilli were present in the protoporphyrin-perfused livers examined by transmission electron microscopy. Although ultraviolet microscopy showed diffuse fluorescence of the hepatocytes and canaliculi of protoporphyrin-perfused livers, the deposition of protoporphyrin in amorphous or crystalline forms was

19. Fifty Years of Climate Curricular Confusion and Pedagogical Gaps

McCaffrey, M. S.; Buhr, S. S.; Niepold, F.

2008-12-01

The processes of weather and climate, including the greenhouse effect and the potential for significant, even catastrophic human impacts on the climate system, were sufficiently understood in 1958 during the International Geophysical Year that the authors of the science education booklet, Planet Earth, The Mystery with 100,000 Clues, published by the U.S. National Academy of Sciences, were confident to predict that continued emissions of carbon dioxide into the atmosphere could, in time, melt icecaps and glaciers and rise sea levels. This important scientific insight was further studied by climatologists, but is largely missing as an integral, important component of science education. Now, fifty years later, with a global population that has doubled, fossil fuel emissions that have tripled, and current energy consumption and emission trajectories that are above the IPCC Business as Usual scenario, leading politicians still doubt that our global economy can impact the climate system. NRC estimates that up to 40 percent of the approximately \$10 trillion U.S. economy is affected by weather and climate events annually, making it a crucial if not dominant factor in our economic well-being, particularly for future generations. Despite the long term and short term importance of climate in our lives, society is essentially illiterate about climate science and confused about the connections between energy, economy and climate, as numerous public opinion polls and studies have shown. A key reason is that education programs and pedagogical content knowledge focusing on the basics of climate, including natural variability as well as human induced climate change, are largely missing from K12 and undergraduate education. Climate has fallen through disciplinary cracks, been avoided because of perceived controversy, and neglected because most educators lack training or expertise in the subject matter. With a focus on climate in formal education, this paper will provide an overview

20. Optical modeling toward optimizing monitoring of intestinal perfusion in trauma patients

SciTech Connect

Akl, Tony; Wilson, Mark A.; Ericson, Milton Nance; Cote, Gerard L.

2013-01-01

Trauma is the number one cause of death for people between the ages 1 and 44 years in the United States. In addition, according to the Centers of Disease Control and Prevention, injury results in over 31 million emergency department visits annually. Minimizing the resuscitation period in major abdominal injuries increases survival rates by correcting impaired tissue oxygen delivery. Optimization of resuscitation requires a monitoring method to determine sufficient tissue oxygenation. Oxygenation can be assessed by determining the adequacy of tissue perfusion. In this work, we present the design of a wireless perfusion and oxygenation sensor based on photoplethysmography. Through optical modeling, the benefit of using the visible wavelengths 470, 525 and 590nm (around the 525nm hemoglobin isobestic point) for intestinal perfusion monitoring is compared to the typical near infrared (NIR) wavelengths (805nm isobestic point) used in such sensors. Specifically, NIR wavelengths penetrate through the thin intestinal wall (~4mm) leading to high background signals. However, these visible wavelengths have two times shorter penetration depth that the NIR wavelengths. Monte-Carlo simulations show that the transmittance of the three selected wavelengths is lower by 5 orders of magnitude depending on the perfusion state. Due to the high absorbance of hemoglobin in the visible range, the perfusion signal carried by diffusely reflected light is also enhanced by an order of magnitude while oxygenation signal levels are maintained. In addition, short source-detector separations proved to be beneficial for limiting the probing depth to the thickness of the intestinal wall.

1. Characterization of renal parenchymal perfusion during experimental infrarenal aortic clamping and declamping with enhanced thermodiffusion electrodes.

PubMed

Kraus, T; Mehrabi, A; Angelescu, M; Golling, M; Allenberg, J R; Klar, E

2001-07-01

Despite multiple previous experimental and clinical investigations, it has not been fully clarified until now whether infrarenal aortic cross-clamping (IRAC) induces a significant disturbance of renal parenchymal perfusion. Most renal cortical flow data collected thus far have been heterogenous because of inherent limitations of available measurement technology. The enhanced thermal diffusion (TD) electrode is a newly developed and previously validated prototype device that allows continuous quantification of parenchymal kidney perfusion after local probe implantation. We monitored renal perfusion during experimental IRAC with TD for the first time, thereby also evaluating the potential applicability of the method in clinical aortic surgery. IRAC (20 min) followed by sudden declamping was performed in pigs under general anesthesia (n = 14). Renal cortical blood flow (RCBF) was continuously quantified by TD, total aortic flow (TABF) and renal artery flow (RABF) were measured by ultrasonic flow probes, and parameters of systemic circulation were determined by Swan-Ganz catheter. Our results showed that kidney perfusion can be continuously quantified using TD electrodes during experimental aortic surgery in a porcine model. IRAC does not lead to a significant impairment of RCBF in young pigs as measured by TD. Renal perfusion appears to be predominantly pressure driven. Consequently, abrubt aortic declamping can bring about prolonged renal ischemia. Transfer of the TD method to RCBF monitoring during clinical aortic surgery appears to be feasible and should be investigated in selected cases.

2. Diffusion MRI

Fukuyama, Hidenao

Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.

3. The Mouse Isolated Perfused Kidney Technique.

PubMed

Czogalla, Jan; Schweda, Frank; Loffing, Johannes

2016-11-17

The mouse isolated perfused kidney (MIPK) is a technique for keeping a mouse kidney under ex vivo conditions perfused and functional for 1 hr. This is a prerequisite for studying the physiology of the isolated organ and for many innovative applications that may be possible in the future, including perfusion decellularization for kidney bioengineering or the administration of anti-rejection or genome-editing drugs in high doses to prime the kidney for transplantation. During the time of the perfusion, the kidney can be manipulated, renal function can be assessed, and various pharmaceuticals administered. After the procedure, the kidney can be transplanted or processed for molecular biology, biochemical analysis, or microscopy. This paper describes the perfusate and the surgical technique needed for the ex vivo perfusion of mouse kidneys. Details of the perfusion apparatus are given and data are presented showing the viability of the kidney's preparation: renal blood flow, vascular resistance, and urine data as functional, transmission electron micrographs of different nephron segments as morphological readouts, and western blots of transport proteins of different nephron segments as molecular readout.

4. MATERNAL ROLE CONFUSION: RELATIONS TO MATERNAL ATTACHMENT AND MOTHER–CHILD INTERACTION FROM INFANCY TO ADOLESCENCE

PubMed Central

VULLIEZ-COADY, LAURIANE; OBSUTH, INGRID; TORREIRO-CASAL, MONICA; ELLERTSDOTTIR, LYDIA; LYONS-RUTH, KARLEN

2014-01-01

Self-reports of role confusion with the parent in childhood are associated with a variety of adverse outcomes. However, role-confusion has been studied primarily from the point of view of the child. The current study evaluated an instrument for assessing role confusion from maternal interviews rather than from child observations or self-reports in adulthood. Fifty-one mothers participating in a longitudinal study since their own child’s infancy were administered the Experiences of Caregiving Interview (C. George & J. Solomon, 1996) when the child was age 20. Interviews were coded using the newly developed Parental Assessment of Role Confusion (PARC; L. Vulliez-Coady & K. Lyons-Ruth, 2009). Maternal PARC scores were related to observational measures of role-confusion in interaction with the child both in infancy and late adolescence. PARC scores also were related to mothers’ hostile-helpless states of mind on the Adult Attachment Interview (C. George, N. Kaplan, & M. Main, 1984, 1985, 1986) and to the extent of Unresolved loss, but not Unresolved Trauma. PARC scores also were related to mothers’ self-reports of helplessness experienced in the parenting role. Discriminant validity of the PARC was demonstrated in that role confusion on the PARC was not related to hostile or disoriented forms of parent–child interaction. Implications for clinical assessment of role confusion are discussed. PMID:25544789

5. The use of confusion patterns to evaluate the neural basis for concurrent vowel identification.

PubMed

Chintanpalli, Ananthakrishna; Heinz, Michael G

2013-10-01

Normal-hearing listeners take advantage of differences in fundamental frequency (F0) to segregate competing talkers. Computational modeling using an F0-based segregation algorithm and auditory-nerve temporal responses captures the gradual improvement in concurrent-vowel identification with increasing F0 difference. This result has been taken to suggest that F0-based segregation is the basis for this improvement; however, evidence suggests that other factors may also contribute. The present study further tested models of concurrent-vowel identification by evaluating their ability to predict the specific confusions made by listeners. Measured human confusions consisted of at most one to three confusions per vowel pair, typically from an error in only one of the two vowels. An improvement due to F0 difference was correlated with spectral differences between vowels; however, simple models based on acoustic and cochlear spectral patterns predicted some confusions not made by human listeners. In contrast, a neural temporal model was better at predicting listener confusion patterns. However, the full F0-based segregation algorithm using these neural temporal analyses was inconsistent across F0 difference in capturing listener confusions, being worse for smaller differences. The inability of this commonly accepted model to fully account for listener confusions suggests that other factors besides F0 segregation are likely to contribute.

6. The use of confusion patterns to evaluate the neural basis for concurrent vowel identificationa

PubMed Central

Chintanpalli, Ananthakrishna; Heinz, Michael G.

2013-01-01

Normal-hearing listeners take advantage of differences in fundamental frequency (F0) to segregate competing talkers. Computational modeling using an F0-based segregation algorithm and auditory-nerve temporal responses captures the gradual improvement in concurrent-vowel identification with increasing F0 difference. This result has been taken to suggest that F0-based segregation is the basis for this improvement; however, evidence suggests that other factors may also contribute. The present study further tested models of concurrent-vowel identification by evaluating their ability to predict the specific confusions made by listeners. Measured human confusions consisted of at most one to three confusions per vowel pair, typically from an error in only one of the two vowels. An improvement due to F0 difference was correlated with spectral differences between vowels; however, simple models based on acoustic and cochlear spectral patterns predicted some confusions not made by human listeners. In contrast, a neural temporal model was better at predicting listener confusion patterns. However, the full F0-based segregation algorithm using these neural temporal analyses was inconsistent across F0 difference in capturing listener confusions, being worse for smaller differences. The inability of this commonly accepted model to fully account for listener confusions suggests that other factors besides F0 segregation are likely to contribute. PMID:24116434

7. Induction of Hepatic and Endothelial Differentiation by Perfusion in a Three-Dimensional Cell Culture Model of Human Fetal Liver

PubMed Central

Pekor, Christopher; Gerlach, Jörg C.; Nettleship, Ian

2015-01-01

The development of functional engineered tissue constructs depends on high cell densities and appropriate vascularization. In this study we implemented a four-compartment three-dimensional perfusion bioreactor culture model for studying the effects of medium perfusion on endothelial, hepatic, and hematopoietic cell populations of primary human fetal liver in an in vivo-like environment. Human fetal liver cells were cultured in bioreactors configured to provide either perfusion or diffusion conditions. Metabolic activities of the cultures were monitored daily by measuring glucose consumption and lactate production. Cell viability during culture was analyzed by lactate dehydrogenase activity. Hepatic functionality was determined by the release of albumin and alpha-fetoprotein (AFP) in culture medium samples. After 4 days of culture, cells were analyzed for the expression of a variety of endothelial, hepatic, and hematopoietic genes, as well as the surface marker expression of CD31 and CD34 in flow cytometry. We found that medium perfusion increased the gene expression of endothelial markers such as CD31, von Willebrand factor (vWF), CD140b, CD309, and CD144 while decreasing the gene expression of the erythrocyte-surface marker CD235a. Hepatic differentiation was promoted under perfusion conditions as demonstrated by lower AFP and higher albumin secretion compared with cultures not exposed to medium perfusion. Additionally, cultures exposed to medium perfusion gave higher rates of glucose consumption and lactate production, indicating increased metabolic activity. In conclusion, high-density bioreactors configured to provide constant medium perfusion significantly induced hepatic and endothelial cell differentiation and provided improved conditions for the culture of human fetal liver cells compared with cultures without perfusion. PMID:25559936

8. Induction of Hepatic and Endothelial Differentiation by Perfusion in a Three-Dimensional Cell Culture Model of Human Fetal Liver.

PubMed

Pekor, Christopher; Gerlach, Jörg C; Nettleship, Ian; Schmelzer, Eva

2015-07-01

The development of functional engineered tissue constructs depends on high cell densities and appropriate vascularization. In this study we implemented a four-compartment three-dimensional perfusion bioreactor culture model for studying the effects of medium perfusion on endothelial, hepatic, and hematopoietic cell populations of primary human fetal liver in an in vivo-like environment. Human fetal liver cells were cultured in bioreactors configured to provide either perfusion or diffusion conditions. Metabolic activities of the cultures were monitored daily by measuring glucose consumption and lactate production. Cell viability during culture was analyzed by lactate dehydrogenase activity. Hepatic functionality was determined by the release of albumin and alpha-fetoprotein (AFP) in culture medium samples. After 4 days of culture, cells were analyzed for the expression of a variety of endothelial, hepatic, and hematopoietic genes, as well as the surface marker expression of CD31 and CD34 in flow cytometry. We found that medium perfusion increased the gene expression of endothelial markers such as CD31, von Willebrand factor (vWF), CD140b, CD309, and CD144 while decreasing the gene expression of the erythrocyte-surface marker CD235a. Hepatic differentiation was promoted under perfusion conditions as demonstrated by lower AFP and higher albumin secretion compared with cultures not exposed to medium perfusion. Additionally, cultures exposed to medium perfusion gave higher rates of glucose consumption and lactate production, indicating increased metabolic activity. In conclusion, high-density bioreactors configured to provide constant medium perfusion significantly induced hepatic and endothelial cell differentiation and provided improved conditions for the culture of human fetal liver cells compared with cultures without perfusion.

9. Plasmapause diffusion

NASA Technical Reports Server (NTRS)

Horwitz, J. L.

1983-01-01

The Bohm diffusion coefficient and observed electrostatic wave scattering are used as the bases of estimates of the smoothing effect that diffusion may have on steep plasmapause density gradients. The estimate for diffusion resulting from scattering by observed electrostatic waves is found to be much lower than that of the perpendicular Bohm diffusion coefficient for characteristic plasma temperatures and magnetic fields. This diffusion rate estimate may be too small, however, if the wave amplitudes are significantly higher for steep plasmapauses. The effects are therefore negligible for most considerations of macroscopic plasmapause dynamics, but may be significant in limiting drift wave instabilities and similar phenomena driven by the steepness of the plasmapause density gradient.

10. Ventilation-perfusion imaging in pulmonary papillomatosis.

PubMed

Espinola, D; Rupani, H; Camargo, E E; Wagner, H N

1981-11-01

Three children with laryngeal papillomas involving the lungs had serial ventilation-perfusion scintigrams to assess results of therapy designed to reduce the bronchial involvement. Different imaging patterns were observed depending on size, number, and location of lesions. In early parenchymal involvement a ventilation-perfusion mismatch was seen. The initial and follow-up studies correlated well with clinical and radiographic findings. This noninvasive procedure is helpful in evaluating ventilatory and perfusion impairment in these patients as well as their response to treatment.

11. Ventilation-perfusion imaging in pulmonary papillomatosis

SciTech Connect

Espinola, D.; Rupani, H.; Camargo, E.E.; Wagner, H.N. Jr.

1981-11-01

Three children with laryngeal papillomas involving the lungs had serial ventilation-perfusion scintigrams to assess results of therapy designed to reduce the bronchial involvement. Different imaging patterns were observed depending on size, number, and location of lesions. In early parenchymal involvement a ventilation-perfusion mismatch was seen. The initial and follow-up studies correlated well with clinical and radiographic findings. This noninvasive procedure is helpful in evaluating ventilatory and perfusion impairment in these patients as well as their response to treatment.

12. 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

13. Cochlear perfusion with a viscous fluid

PubMed Central

Wang, Yi; Olson, Elizabeth S.

2016-01-01

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 withdrawnfrom 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, while in cochleae perfused with 0.125% and 0.25% HA Reissner’s membrane (RM) was torn. Thus, the CAP threshold elevation was likely due to the broken of RM, which 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

14. Distinctive Patterns of Three-Dimensional Arterial Spin-Labeled Perfusion Magnetic Resonance Imaging in Subtypes of Acute Ischemic Stroke.

PubMed

Kohno, Naoto; Okada, Kazunori; Yamagata, Shingo; Takayoshi, Hiroyuki; Yamaguchi, Shuhei

2016-07-01

Ischemic penumbra in acute ischemic stroke (AIS) can be evaluated using arterial spin-labeled (ASL) perfusion magnetic resonance imaging (MRI). We used three-dimensional ASL-MRI to examine patients with different stroke subtypes and the clinical utility of the method within 24 hours of AIS onset. The 55 male and 48 female patients (mean age, 79.0 years) underwent diffusion-weighted imaging (DWI), fluid-attenuated inversion recovery imaging, magnetic resonance angiography, and pulsed continuous ASL perfusion imaging to determine stroke subtype, hypoperfused ASL area, and neurological deficit severity (National Institutes of Health Stroke Scale). Arterial transit artifacts, indicative of occlusive regions or collateral flow, and other stroke indices were compared. ASL hypoperfusion was detected in 3 of 9 patients with transient ischemic attack (TIA), 2 of 27 patients with lacunar infarction (LI), 19 of 31 patients with atherothrombotic infarction (AT), and 30 of 36 patients with cardiogenic embolic infarction (CE). ASL abnormalities were significantly less frequent in LI than in AT and CE, and more frequent in CE than in TIA. ASL abnormalities were more prevalent in patients with medium-to-large DWI-assessed lesions than in those with small lesions on DWI. Patients with medium-sized lesions following AT and CE had a high frequency of diffusion-perfusion mismatch. In 4 of the 5 patients who underwent intravenous thrombolytic therapy, ASL hypoperfusion and diffusion-perfusion mismatch were improved and the occluded arteries were recanalized. ASL perfusion studies may provide useful clinical information allowing diffusion-perfusion mismatch detection and treatment selection in AIS patients, depending on stroke subtype. Copyright © 2016 National Stroke Association. Published by Elsevier Inc. All rights reserved.

15. Evolution of pulmonary perfusion defects demonstrated with contrast-enhanced dynamic MR perfusion imaging.

PubMed

Howarth, N R; Beziat, C; Berthezène, Y

1999-01-01

Pulmonary perfusion defects can be demonstrated with contrast-enhanced dynamic MR perfusion imaging. We present the case of a patient with a pulmonary artery sarcoma who presented with a post-operative pulmonary embolus and was followed in the post-operative period with dynamic contrast-enhanced MR perfusion imaging. This technique allows rapid imaging of the first passage of contrast material through the lung after bolus injection in a peripheral vein. To our knowledge, this case report is the first to describe the use of this MR technique in showing the evolution of peripheral pulmonary perfusion defects associated with pulmonary emboli.

16. 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

17. The use of source memory to identify one's own episodic confusion errors.

PubMed

Smith, S M; Tindell, D R; Pierce, B H; Gilliland, T R; Gerkens, D R

2001-03-01

In 4 category cued recall experiments, participants falsely recalled nonlist common members, a semantic confusion error. Errors were more likely if critical nonlist words were presented on an incidental task, causing source memory failures called episodic confusion errors. Participants could better identify the source of falsely recalled words if they had deeply processed the words on the incidental task. For deep but not shallow processing, participants could reliably include or exclude incidentally shown category members in recall. The illusion that critical items actually appeared on categorized lists was diminished but not eradicated when participants identified episodic confusion errors post hoc among their own recalled responses; participants often believed that critical items had been on both the incidental task and the study list. Improved source monitoring can potentially mitigate episodic (but not semantic) confusion errors.

18. A Comparison of the Effects of Filtering and Sensorineural Hearing Loss on Patterns of Consonant Confusions

ERIC Educational Resources Information Center

Wang, Marilyn D.; And Others

1978-01-01

The study determined whether eight undergraduate normal listeners, presented with filtered speech, would produce consonant confusions similar to those previously reported for the hearing-impaired listener. (Author/SBH)

19. Comparison of heterogeneity quantification algorithms for brain SPECT perfusion images

PubMed Central

2012-01-01

Background Several algorithms from the literature were compared with the original random walk (RW) algorithm for brain perfusion heterogeneity quantification purposes. Algorithms are compared on a set of 210 brain single photon emission computed tomography (SPECT) simulations and 40 patient exams. Methods Five algorithms were tested on numerical phantoms. The numerical anthropomorphic Zubal head phantom was used to generate 42 (6 × 7) different brain SPECT simulations. Seven diffuse cortical heterogeneity levels were simulated with an adjustable Gaussian noise function and six focal perfusion defect levels with temporoparietal (TP) defects. The phantoms were successively projected and smoothed with Gaussian kernel with full width at half maximum (FWHM = 5 mm), and Poisson noise was added to the 64 projections. For each simulation, 5 Poisson noise realizations were performed yielding a total of 210 datasets. The SPECT images were reconstructed using filtered black projection (Hamming filter: α = 0.5). The five algorithms or measures tested were the following: the coefficient of variation, the entropy and local entropy, fractal dimension (FD) (box counting and Fourier power spectrum methods), the gray-level co-occurrence matrix (GLCM), and the new RW. The heterogeneity discrimination power was obtained with a linear regression for each algorithm. This regression line is a mean function of the measure of heterogeneity compared to the different diffuse heterogeneity and focal defect levels generated in the phantoms. A greater slope denotes a larger separation between the levels of diffuse heterogeneity. The five algorithms were computed using 40 99mTc-ethyl-cysteinate-dimer (ECD) SPECT images of patients referred for memory impairment. Scans were blindly ranked by two physicians according to the level of heterogeneity, and a consensus was obtained. The rankings obtained by the algorithms were compared with the physicians' consensus ranking. Results The GLCM method

20. Comparison of heterogeneity quantification algorithms for brain SPECT perfusion images.

PubMed

Modzelewski, Romain; Janvresse, Elise; de la Rue, Thierry; Vera, Pierre

2012-07-20

Several algorithms from the literature were compared with the original random walk (RW) algorithm for brain perfusion heterogeneity quantification purposes. Algorithms are compared on a set of 210 brain single photon emission computed tomography (SPECT) simulations and 40 patient exams. Five algorithms were tested on numerical phantoms. The numerical anthropomorphic Zubal head phantom was used to generate 42 (6 × 7) different brain SPECT simulations. Seven diffuse cortical heterogeneity levels were simulated with an adjustable Gaussian noise function and six focal perfusion defect levels with temporoparietal (TP) defects. The phantoms were successively projected and smoothed with Gaussian kernel with full width at half maximum (FWHM = 5 mm), and Poisson noise was added to the 64 projections. For each simulation, 5 Poisson noise realizations were performed yielding a total of 210 datasets. The SPECT images were reconstructed using filtered black projection (Hamming filter: α = 0.5).The five algorithms or measures tested were the following: the coefficient of variation, the entropy and local entropy, fractal dimension (FD) (box counting and Fourier power spectrum methods), the gray-level co-occurrence matrix (GLCM), and the new RW.The heterogeneity discrimination power was obtained with a linear regression for each algorithm. This regression line is a mean function of the measure of heterogeneity compared to the different diffuse heterogeneity and focal defect levels generated in the phantoms. A greater slope denotes a larger separation between the levels of diffuse heterogeneity.The five algorithms were computed using 40 99mTc-ethyl-cysteinate-dimer (ECD) SPECT images of patients referred for memory impairment. Scans were blindly ranked by two physicians according to the level of heterogeneity, and a consensus was obtained. The rankings obtained by the algorithms were compared with the physicians' consensus ranking. The GLCM method (slope = 58.5), the fractal

1. 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.

2. 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.

3. 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

4. Brain perfusion in acute and chronic hyperglycemia in rats

SciTech Connect

Kikano, G.E.; LaManna, J.C.; Harik, S.I. )

1989-08-01

Recent studies show that acute and chronic hyperglycemia cause a diffuse decrease in regional cerebral blood flow and that chronic hyperglycemia decreases the brain L-glucose space. Since these changes can be caused by a decreased density of perfused brain capillaries, we used 30 adult male Wistar rats to study the effect of acute and chronic hyperglycemia on (1) the brain intravascular space using radioiodinated albumin, (2) the anatomic density of brain capillaries using alkaline phosphatase histochemistry, and (3) the fraction of brain capillaries that are perfused using the fluorescein isothiocyanate-dextran method. Our results indicate that acute and chronic hyperglycemia do not affect the brain intravascular space nor the anatomic density of brain capillaries. Also, there were no differences in capillary recruitment among normoglycemic, acutely hyperglycemic, and chronically hyperglycemic rats. These results suggest that the shrinkage of the brain L-glucose space in chronic hyperglycemia is more likely due to changes in the blood-brain barrier permeability to L-glucose.

5. Griffith diffusers

NASA Technical Reports Server (NTRS)

Yang, T.-T.; Nelson, C. D.

1979-01-01

Contoured wall diffusers are designed by using an inverse method. The prescribed wall velocity distribution(s) was taken from the high lift airfoil designed by A. A. Griffith in 1938; therefore, such diffusers are named Griffith diffusers. First the formulation of the inverse problem and the method of solution are outlined. Then the typical contour of a two-dimensional diffuser and velocity distributions across the flow channel at various stations are presented. For a Griffith diffuser to operate as it is designed, boundary layer suction is necessary. Discussion of the percentage of through-flow required to be removed for the purpose of boundary layer control is given. Finally, reference is made to the latest version of a computer program for a two-dimensional diffuser requiring only area ratio, nondimensional length and suction percentage as inputs.

6. Griffith diffusers

NASA Technical Reports Server (NTRS)

Yang, T.-T.; Nelson, C. D.

1979-01-01

Contoured wall diffusers are designed by using an inverse method. The prescribed wall velocity distribution(s) was taken from the high lift airfoil designed by A. A. Griffith in 1938; therefore, such diffusers are named Griffith diffusers. First the formulation of the inverse problem and the method of solution are outlined. Then the typical contour of a two-dimensional diffuser and velocity distributions across the flow channel at various stations are presented. For a Griffith diffuser to operate as it is designed, boundary layer suction is necessary. Discussion of the percentage of through-flow required to be removed for the purpose of boundary layer control is given. Finally, reference is made to the latest version of a computer program for a two-dimensional diffuser requiring only area ratio, nondimensional length and suction percentage as inputs.

7. Role of perfusion imaging in acute stroke.

PubMed

Sillanpää, N

2013-03-01

Imaging has a central role in the diagnosis and classification of acute stroke, the triage of patients to different treatment approaches and the prediction of the clinical outcome and the risk of hemorrhagic complications. A multimodal imaging protocol that includes a perfusion study allows diagnostics beyond anatomical findings by enabling the characterization of the ischemic brain tissue and the cerebral hemodynamic state. This information potentially leads to more accurate clinical decision making with the intention to select the right patients for different revascularization therapies regardless of fixed time windows. Perfusion imaging enables the detection and quantification of the irreversibly damaged infarct core and the at-risk penumbra. Parameters derived from perfusion studies can serve as surrogate markers for stroke severity and are independent predictors of the clinical outcome and the occurrence of hemorrhagic complications. The validation and standardization of the perfusion methodology is still ongoing. Currently there is emerging but no high level evidence that perfusion imaging improves the clinical outcome or has a direct impact on the decision to treat the patient with intravenous thrombolytic therapy or intra-arterial interventions. Thus, definite guidelines on the role of the perfusion imaging in the context of acute stroke cannot yet be given.

8. Hydroxyethyl starch solution for extracorporeal tissue perfusion.

PubMed

Taeger, Christian D; Friedrich, Oliver; Drechsler, Caroline; Weigand, Annika; Hobe, Frieder; Geppert, Carol I; Münch, Frank; Birkholz, Torsten; Buchholz, Rainer; Horch, Raymund E; Präbst, Konstantin

2016-11-04

In the field of free flap transfer in reconstructive surgery, the trans- or replanted tissue always undergoes cell damage during ischemia to a more or less strong extent. In previous studies we already showed that conserving muscle transplants by means of extracorporeal perfusion over a period of 6 hours by using a crystalloid solution for perfusion. However, we observed significant edema formation. In this study we aimed at reducing the edema formation by using an iso-oncotic colloid as perfusion solution. This way we wanted to evaluate a possible new application of hydroxyl-ethyl starch in an extracorporeal setup to exploit potential benefits of the colloid.Examined parameters include the muscles' functionality with external field stimulation, histological examination and edema formation. Perfused muscles showed a statistically significant higher ability to exert force compared to nonperfused ones. These findings can be confirmed using Annexin V as marker for cell damage, as perfusion of muscle tissue limits damage significantly compared to nonperfused tissue. Substituting the electrolyte perfusion solution with a colloidal one shows the tendency to reduce the edema formation however without statistical significance.

9. Detection and prediction limits for identifying highly confusable drug names from experimental data.

PubMed

Lambert, Bruce L; Bhaumik, Runa; Zhao, Weihan; Bhaumik, Dulal K

2016-01-01

Confusions between drug names that look and sound alike are common, costly, harmful, and difficult to prevent. One prevention strategy is to screen proposed new drug names for confusability before approving them. Widespread acceptance of preapproval tests of confusability is compromised by the lack of experimental designs and statistical methods to support valid inferences about whether a proposed new name is unacceptably confusing. One way of identifying confusing names is to conduct memory and perception experiments on a set of drug names which would include both the new name and a set of control names (e.g., names already on the market). The experiment would yield an observed error rate for every name. Inferences about the acceptability of the new name can be made by comparing the error rate of the new name to the distribution of error rates of the control names. We describe four memory and perception experiments on drug names, carried out using clinicians as participants. Each experiment included drug names designated as test and control names. We demonstrate how to use a combination of logistic regression, Poisson prediction limits, and highly assured credible intervals to identify and apply a threshold for identifying unacceptably confusing names. Our models show an excellent fit to the data. These experimental designs and analytic methods should be useful in the preapproval testing of proposed new drug names and in similar regulatory scenarios where it is necessary to draw inferences about the comparative safety or effectiveness of new vs. old products.

10. Experiences with the magnetism of conducting loops: Historical instruments, experimental replications, and productive confusions

Cavicchi, Elizabeth

2003-02-01

This study investigates nineteenth century laboratory work on electromagnetism through historical accounts and experimental replications. Oersted found that when a magnetic needle was placed in varying positions around a conducting wire, its orientation changed: in moving from a spot above the wire to one below, its sense inverted. This behavior was confusing and provocative. Early experimenters such as Johann Schweigger, Johann Poggendorff, and James Cumming engaged it by bending wire into loops. These loops, which increased the magnetic effect on a compass placed within, also provided evidence of their understanding and confusion. Coiling conducting wires around iron magnetized it, but when some wires coiled oppositely from others, the effect diminished. This effect confused contemporaries of Joseph Henry who made electromagnets, and amateurs later in the century who constructed multisection induction coils. I experienced these confusions myself while working with multilayer coils and induction coils that I made to replicate the historical instruments. This study shows how confusion can be a productive element in learning, by engaging learners to ask questions and invent experiments. By providing space for learners' confusions, teachers can support the development of their students' physical understandings.

11. The relationship between magical thinking, inferential confusion and obsessive-compulsive symptoms.

PubMed

Goods, N A R; Rees, C S; Egan, S J; Kane, R T

2014-01-01

Inferential confusion is an under-researched faulty reasoning process in obsessive-compulsive disorder (OCD). Based on an overreliance on imagined possibilities, it shares similarities with the extensively researched construct of thought-action fusion (TAF). While TAF has been proposed as a specific subset of the broader construct of magical thinking, the relationship between inferential confusion and magical thinking is unexplored. The present study investigated this relationship, and hypothesised that magical thinking would partially mediate the relationship between inferential confusion and obsessive-compulsive symptoms. A non-clinical sample of 201 participants (M = 34.94, SD = 15.88) were recruited via convenience sampling. Regression analyses found the hypothesised mediating relationship was supported, as magical thinking did partially mediate the relationship between inferential confusion and OC symptoms. Interestingly, inferential confusion had the stronger relationship with OC symptoms in comparison to the other predictor variables. Results suggest that inferential confusion can both directly and indirectly (via magical thinking) impact on OC symptoms. Future studies with clinical samples should further investigate these constructs to determine whether similar patterns emerge, as this may eventually inform which cognitive errors to target in treatment of OCD.

12. Perfusion weighted imaging and its application in stroke

Li, Enzhong; Tian, Jie; Han, Ying; Wang, Huifang; Li, Xingfeng; Zhu, Fuping

2003-05-01

To study the technique and application of perfusion weighted imaging (PWI) in the diagnosis and medical treatment of acute stroke, 25 patients were examined by 1.5 T or 1.0 T MRI scanner. The Data analysis was done with "3D Med System" developed by our Lab to process the data and obtain apparent diffusion coefficient (ADC) map, cerebral blood volume (CBV) map, cerebral blood flow (CBF) map as well as mean transit time (MTT) map. In accute stage of stroke, normal or slightly hypointensity in T1-, hyperintensity in T2- and diffusion-weighted images were seen in the cerebral infarction areas. There were hypointensity in CBV map, CBF map and ADC map; and hyperintensity in MTT map that means this infarct area could be saved. If the hyperintensity area in MTT map was larger than the area in diffusion weighted imaging (DWI), the larger part was called penumbra and could be cured by an appropriate thrombolyitic or other therapy. The CBV, CBF and MTT maps are very important in the diagnosis and medical treatment of acute especially hyperacute stroke. Comparing with DWI, we can easily know the situation of penumbra and the effect of curvative therapy. Besides, we can also make a differential diagnosis with this method.

13. Fluorescence-based enhanced reality (FLER) for real-time estimation of bowel perfusion in minimally invasive surgery

Diana, Michele

2016-03-01

Pre-anastomotic bowel perfusion is a key factor for a successful healing process. Clinical judgment has limited accuracy to evaluate intestinal microperfusion. Fluorescence videography is a promising tool for image-guided intraoperative assessment of the bowel perfusion at the future anastomotic site in the setting of minimally invasive procedures. The standard configuration for fluorescence videography includes a Near-Infrared endoscope able to detect the signal emitted by a fluorescent dye, more frequently Indocyanine Green (ICG), which is administered by intravenous injection. Fluorescence intensity is proportional to the amount of fluorescent dye diffusing in the tissue and consequently is a surrogate marker of tissue perfusion. However, fluorescence intensity alone remains a subjective approach and an integrated computer-based analysis of the over-time evolution of the fluorescence signal is required to obtain quantitative data. We have developed a solution integrating computer-based analysis for intra-operative evaluation of the optimal resection site, based on the bowel perfusion as determined by the dynamic fluorescence intensity. The software can generate a "virtual perfusion cartography", based on the "fluorescence time-to-peak". The virtual perfusion cartography can be overlapped onto real-time laparoscopic images to obtain the Enhanced Reality effect. We have defined this approach FLuorescence-based Enhanced Reality (FLER). This manuscript describes the stepwise development of the FLER concept.

14. Arterial Spin Labeling Perfusion Magnetic Resonance Imaging Performed in Acute Perinatal Stroke Reveals Hyperperfusion Associated With Ischemic Injury.

PubMed

Watson, Christopher G; Dehaes, Mathieu; Gagoski, Borjan A; Grant, P Ellen; Rivkin, Michael J

2016-06-01

Perfusion-weighted imaging in adults with acute stroke often reveals hypoperfusion in the ischemic core and in a surrounding area of nondiffusion-restricted penumbral tissue. Perinatal stroke is common, but the perfusion pattern is rarely documented. We aimed to describe the perfusion pattern in newborns with perinatal stroke. Neonates with clinical features of acute stroke underwent magnetic resonance imaging. Perfusion data were obtained using pseudocontinuous arterial spin labeling. Strokes were classified as arterial, venous, or both. Core infarction was determined by the presence of restricted diffusion on diffusion-weighted imaging. Perfusion-weighted imaging and susceptibility-weighted imaging signal in the ischemic area were visually compared with the homologous region in the contralesional hemisphere. Electroencephalogram data were evaluated for seizure activity. In 25 neonates with acute stroke, 8 of 11 (73%) with arterial ischemic stroke demonstrated hyperperfusion, 1 of 9 (11%) with venous stroke, and 4 of 5 (80%) with both. Hypoperfusion was observed in 3 of 9 (33%) with venous and none with arterial ischemic stroke. Perfusion was normal in 4 of 9 (45%) with venous and 1 of 5 (20%) with both. Twenty-one of 24 patients (88%) with electroencephalogram data had either electrographic seizures or focal sharp waves in the ipsilesional hemisphere (11/11 arterial ischemic stroke, 6/9 venous, and 4/5 both). Perfusion-weighted imaging can be obtained in neonates with acute stroke and often reveals hyperperfusion in the infarct core. Penumbra in arterial ischemic stroke is seldom found. Hyperperfusion may be caused by poststroke reperfusion or to neuronal hyperexcitability of stroke-associated seizure. Its identification may be useful for consideration of therapy for acute neonatal stroke. © 2016 American Heart Association, Inc.

15. Perfusion and pH MRI in familial hemiplegic migraine with prolonged aura.

PubMed

Blicher, Jakob Udby; Tietze, Anna; Donahue, Manus J; Smith, Seth A; Østergaard, Leif

2016-03-01

To investigate tissue flow disturbance and hypoxia during migraine aura, we studied a case of familial hemiplegic migraine (FHM) using novel magnetic resonance imaging (MRI) techniques. A 44-year-old male was admitted with suspected stroke because of confusion and aphasia. Initial gadolinium-based perfusion MRI showed a decrease in cerebral blood flow and an increase in capillary flow disturbances within the left hemisphere. Later during the prolonged aura phase, chemical exchange saturation transfer MRI indicated a drop in pH in the affected area. The patient was diagnosed with an R908Q mutation in the ATP1A2 gene causing FHM type 2. During prolonged aura in FHM, MRI shows reduced CBF, capillary flow disturbances and a possible pH drop that could indicate tissue hypoxia. © International Headache Society 2015.

16. Use of spin echo T(2) BOLD in assessment of cerebral misery perfusion at 1.5 T.

PubMed

Kavec, M; Gröhn, O H; Kettunen, M I; Silvennoinen, M J; Penttonen, M; Kauppinen, R A

2001-03-01

Inadequate blood supply relative to metabolic demand, a haemodynamic condition termed as misery perfusion, often occurs in conjunction with acute ischaemic stroke. Misery perfusion results in adaptive changes in cerebral physiology including increased cerebral blood volume (CBV) and oxygen extraction ratio (OER) to secure substrate supply for the brain. It has been suggested that the presence of misery perfusion may be an indication of reversible ischaemia, thus detection of this condition may have clinical impact in acute stroke imaging. The ability of single spin echo T(2) to detect misery perfusion in the rat brain at 1.5 T owing to its sensitivity to blood oxygenation level dependent (BOLD) contrast was studied both theoretically and experimentally. Based on the known physiology of misery perfusion, tissue morphometry and blood relaxation data, T(2) behaviour in misery perfusion was simulated. The interpretation of these computations was experimentally assessed by quantifying T(2) in a rat model for cerebral misery perfusion. CBF was quantified with the H(2) clearance method. A drop of CBF from 58+/-8 to 17+/-3 ml/100 g/min in the parieto-frontal cortex caused shortening of T(2) from 66.9+/-0.4 to 64.6+/-0.5 ms. Under these conditions, no change in diffusion MRI was detected. In contrast, the cortex with CBF of 42+/-7 ml/100 g/min showed no change in T(2). Computer simulations accurately predicted these T(2) responses. The present study shows that the acute drop of CBF by 70% causes a negative BOLD that is readily detectable by T(2) MRI at 1.5 T. Thus BOLD may serve as an index of misery perfusion thus revealing viable tissue with increased OER.

17. Diffusion of Alexa Fluor 488-conjugated dendrimers in rat aortic tissue.

PubMed

Cho, Brenda S; Roelofs, Karen J; Majoros, Istvan J; Baker, James R; Stanley, James C; Henke, Peter K; Upchurch, Gilbert R

2006-11-01

In this study, the distribution of labeled dendrimers in native and aneurysmal rat aortic tissue was examined. Adult male rats underwent infrarenal aorta perfusion with generation 5 (G5) acetylated Alexa Fluor 488-conjugated dendrimers for varying lengths of time. In a second set of experiments, rats underwent aortic elastase perfusion followed by aortic dendrimer perfusion 7 days later. Aortic diameters were measured prior to and postelastase perfusion, and again on the day of harvest. Aortas were harvested 0, 12, or 24 h postperfusion, fixed, and mounted. Native aortas were harvested and viewed as negative controls. Aortic cross-sections were viewed and imaged using confocal microscopy. Dendrimers were quantified (counts/high-powered field). Results were evaluated by repeated measures ANOVA and Student's t-test. We found that in native aortas, dendrimers penetrated the aortic wall in all groups. For all perfusion times, fewer dendrimers were present as time between dendrimer perfusion and aortic harvest increased. Longer perfusion times resulted in increased diffusion of dendrimers throughout the aortic wall. By 24 h, the majority of the dendrimers were through the wall. Dendrimers in aneurysmal aortas, on day 0 postdendrimer perfusion, diffused farther into the aortic wall than controls. In conclusion, this study documents labeled dendrimers delivered intra-arterially to native rat aortas in vivo, and the temporal diffusion of these molecules within the aortic wall. Increasing perfusion time and length of time prior to harvest resulted in continued dendrimer diffusion into the aortic wall. These preliminary data provide a novel mechanism whereby local inhibitory therapy may be delivered locally to aortic tissue.

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

PubMed Central

Ghisleni, Carmen; Bollmann, Steffen; Biason-Lauber, Anna; Poil, Simon-Shlomo; Brandeis, Daniel; Martin, Ernst; Michels, Lars; Hersberger, Martin; Suckling, John

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. PMID:26356576

19. 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.

20. GPU-accelerated voxelwise hepatic perfusion quantification

Wang, H.; Cao, Y.

2012-09-01

Voxelwise quantification of hepatic perfusion parameters from dynamic contrast enhanced (DCE) imaging greatly contributes to assessment of liver function in response to radiation therapy. However, the efficiency of the estimation of hepatic perfusion parameters voxel-by-voxel in the whole liver using a dual-input single-compartment model requires substantial improvement for routine clinical applications. In this paper, we utilize the parallel computation power of a graphics processing unit (GPU) to accelerate the computation, while maintaining the same accuracy as the conventional method. Using compute unified device architecture-GPU, the hepatic perfusion computations over multiple voxels are run across the GPU blocks concurrently but independently. At each voxel, nonlinear least-squares fitting the time series of the liver DCE data to the compartmental model is distributed to multiple threads in a block, and the computations of different time points are performed simultaneously and synchronically. An efficient fast Fourier transform in a block is also developed for the convolution computation in the model. The GPU computations of the voxel-by-voxel hepatic perfusion images are compared with ones by the CPU using the simulated DCE data and the experimental DCE MR images from patients. The computation speed is improved by 30 times using a NVIDIA Tesla C2050 GPU compared to a 2.67 GHz Intel Xeon CPU processor. To obtain liver perfusion maps with 626 400 voxels in a patient's liver, it takes 0.9 min with the GPU-accelerated voxelwise computation, compared to 110 min with the CPU, while both methods result in perfusion parameters differences less than 10-6. The method will be useful for generating liver perfusion images in clinical settings.

1. GPU-accelerated voxelwise hepatic perfusion quantification.

PubMed

Wang, H; Cao, Y

2012-09-07

Voxelwise quantification of hepatic perfusion parameters from dynamic contrast enhanced (DCE) imaging greatly contributes to assessment of liver function in response to radiation therapy. However, the efficiency of the estimation of hepatic perfusion parameters voxel-by-voxel in the whole liver using a dual-input single-compartment model requires substantial improvement for routine clinical applications. In this paper, we utilize the parallel computation power of a graphics processing unit (GPU) to accelerate the computation, while maintaining the same accuracy as the conventional method. Using compute unified device architecture-GPU, the hepatic perfusion computations over multiple voxels are run across the GPU blocks concurrently but independently. At each voxel, nonlinear least-squares fitting the time series of the liver DCE data to the compartmental model is distributed to multiple threads in a block, and the computations of different time points are performed simultaneously and synchronically. An efficient fast Fourier transform in a block is also developed for the convolution computation in the model. The GPU computations of the voxel-by-voxel hepatic perfusion images are compared with ones by the CPU using the simulated DCE data and the experimental DCE MR images from patients. The computation speed is improved by 30 times using a NVIDIA Tesla C2050 GPU compared to a 2.67 GHz Intel Xeon CPU processor. To obtain liver perfusion maps with 626 400 voxels in a patient's liver, it takes 0.9 min with the GPU-accelerated voxelwise computation, compared to 110 min with the CPU, while both methods result in perfusion parameters differences less than 10(-6). The method will be useful for generating liver perfusion images in clinical settings.

2. GPU-Accelerated Voxelwise Hepatic Perfusion Quantification

PubMed Central

Wang, H; Cao, Y

2012-01-01

Voxelwise quantification of hepatic perfusion parameters from dynamic contrast enhanced (DCE) imaging greatly contributes to assessment of liver function in response to radiation therapy. However, the efficiency of the estimation of hepatic perfusion parameters voxel-by-voxel in the whole liver using a dual-input single-compartment model requires substantial improvement for routine clinical applications. In this paper, we utilize the parallel computation power of a graphics processing unit (GPU) to accelerate the computation, while maintaining the same accuracy as the conventional method. Using CUDA-GPU, the hepatic perfusion computations over multiple voxels are run across the GPU blocks concurrently but independently. At each voxel, non-linear least squares fitting the time series of the liver DCE data to the compartmental model is distributed to multiple threads in a block, and the computations of different time points are performed simultaneously and synchronically. An efficient fast Fourier transform in a block is also developed for the convolution computation in the model. The GPU computations of the voxel-by-voxel hepatic perfusion images are compared with ones by the CPU using the simulated DCE data and the experimental DCE MR images from patients. The computation speed is improved by 30 times using a NVIDIA Tesla C2050 GPU compared to a 2.67 GHz Intel Xeon CPU processor. To obtain liver perfusion maps with 626400 voxels in a patient’s liver, it takes 0.9 min with the GPU-accelerated voxelwise computation, compared to 110 min with the CPU, while both methods result in perfusion parameters differences less than 10−6. The method will be useful for generating liver perfusion images in clinical settings. PMID:22892645

3. [An automatic system controlled by microcontroller for carotid sinus perfusion].

PubMed

Yi, X L; Wang, M Y; Fan, Z Z; He, R R

2001-08-01

To establish a new method for controlling automatically the carotid perfusion pressure. A cheap practical automatic perfusion unit based on AT89C2051 micro controller was designed. The unit, LDB-M perfusion pump and the carotid sinus of an animal constituted an automatic perfusion system. This system was able to provide ramp and stepwise updown perfusion pattern and has been used in the research of baroreflex. It can insure the precision and reproducibility of perfusion pressure curve, and improve the technical level in corresponding medical field.

4. In vitro performance of a perfusion and oxygenation optical sensor using a unique liver phantom

Akl, Tony J.; King, Travis J.; Long, Ruiqi; Ericson, M. N.; Wilson, Mark A.; McShane, Michael J.; Coté, Gerard L.

2012-03-01

Between the years 1999 and 2008, on average 2,052 people died per year on the waiting list for liver transplants. Monitoring perfusion and oxygenation in transplanted organs in the 7 to 14 days period post-transplant can enhance graft and patient survival rates, and resultantly increase the availability of organs. In this work, we present in vitro results using a unique liver phantom that support the ability of our sensor to detect perfusion changes in the portal vein at low levels (50 mL/min . 4.5% of normal level). Our sensor measures diffuse reflection from three wavelengths (735, 805 and 940 nm) around the hemoglobin isobestic point (805 nm) to determine perfusion and oxygenation separately. To assess the sensitivity of our sensor to flow changes in the low range, we used two peristaltic pumps to pump a dye solution mimicking the optical properties of oxygenated blood, at various rates, through a PDMS based phantom mimicking the optical properties of liver tissue. The collected pulsatile signal increased by 120% (2.2X) for every 100 mL/min flow rise for all three wavelengths in the range 50 to 500 mL/min. In addition, we used different dye mixtures to mimic oxygenation changes at constant perfusion/flow levels. The optical properties of the dye mixtures mimic oxygen saturations ranging between 0 and 100%. The sensor was shown to be sensitive to changes in oxygen saturations above 50%.

5. In vivo perfusion assessment of an anastomosis surgery on porcine intestinal model (Conference Presentation)

Le, Hanh N. D.; Opferman, Justin; Decker, Ryan; Cheon, Gyeong W.; Kim, Peter C. W.; Kang, Jin U.; Krieger, Axel

2016-04-01

Anastomosis, the connection of two structures, is a critical procedure for reconstructive surgery with over 1 million cases/year for visceral indication alone. However, complication rates such as strictures and leakage affect up to 19% of cases for colorectal anastomoses and up to 30% for visceral transplantation anastomoses. Local ischemia plays a critical role in anastomotic complications, making blood perfusion an important indicator for tissue health and predictor for healing following anastomosis. In this work, we apply a real time multispectral imaging technique to monitor impact on tissue perfusion due to varying interrupted suture spacing and suture tensions. Multispectral tissue images at 470, 540, 560, 580, 670 and 760 nm are analyzed in conjunction with an empirical model based on diffuse reflectance process to quantify the hemoglobin oxygen saturation within the suture site. The investigated tissues for anastomoses include porcine small (jejunum and ileum) and large (transverse colon) intestines. Two experiments using interrupted suturing with suture spacing of 1, 2, and 3 mm and tension levels from 0 N to 2.5 N are conducted. Tissue perfusion at 5, 10, 20 and 30 min after suturing are recorded and compared with the initial normal state. The result indicates the contrast between healthy and ischemic tissue areas and assists the determination of suturing spacing and tension. Therefore, the assessment of tissue perfusion will permit the development and intra-surgical monitoring of an optimal suture protocol during anastomosis with less complications and improved functional outcome.

6. Comparison of scanning beam and whole field laser Doppler perfusion imaging

Steenbergen, Wiendelt; Hondebrink, Erwin; Van Leeuwen, Ton G.; Draijer, Matthijs J.

2010-02-01

Currently, laser perfusion imaging (LDPI) is undergoing a technology shift from scanning beam perfusion imagers to whole field systems. The latter can be subdivided in laser Doppler methods systems based on high speed CMOS cameras, and laser speckle contrast analysis (LASCA) technologies using slow imaging arrays, mostly CCD-based. In scanning beam systems, a collimated laser beam scans the tissue with diffusely back reflected light being captured with a single detector. In whole field systems a large tissue area is illuminated, and the reflected light is imaged onto an array and captured at once. Unlike scanning beam systems, both whole field methods enable perfusion imaging at video rate. In this study we experimentally compare the scanning beam LDPI principle with whole field LDPI, using Intralipid phantoms. For the tissue phantoms, the Monte Carlo simulation technique will be used as a reference. From measurements on Intralipid phantoms compared to Monte Carlo, we conclude that in whole field LDPI the flux image, representing the first order moment of the power spectrum of photocurrent fluctuations is much closer related to real perfusion than for scanning beam systems. This difference can be explained in terms of the different behaviour of dynamic speckle patterns generated in both methods, in response to varying tissue optical properties.

7. Source Memory in Korsakoff Syndrome: Disentangling the Mechanisms of Temporal Confusion.

PubMed

Brion, Mélanie; de Timary, Philippe; Pitel, Anne-Lise; Maurage, Pierre

2017-03-01

Korsakoff syndrome (KS), most frequently resulting from alcohol dependence (ALC), is characterized by severe anterograde amnesia. It has been suggested that these deficits may extend to other memory components, and notably source memory deficits involved in the disorientation and temporal confusion frequently observed in KS. However, the extent of this source memory impairment in KS and its usefulness for the differential diagnosis between ALC and KS remain unexplored. Nineteen patients with KS were compared with 19 alcohol-dependent individuals and 19 controls in a source memory test exploring temporal context confusions ("continuous recognition task"). Episodic memory and psychopathological comorbidities were controlled for. While no source memory deficit was observed in ALC, KS was associated with a significant presence of temporal context confusion, even when the influence of comorbidities was taken into account. This source memory impairment did not appear to be related to performances on episodic memory or executive functions. Patients with KS displayed source memory deficits, as indexed by temporal context confusions. The absence of a relationship with episodic memory performances seems to indicate that source memory impairment is not a mere by-product of amnesia. As ALC was associated with preserved source memory, the presence of temporal context confusion may serve as a complementary tool for the differential diagnosis between ALC and KS. Copyright © 2017 by the Research Society on Alcoholism.

8. A NOVEL TECHNIQUE TO IMPROVE PHOTOMETRY IN CONFUSED IMAGES USING GRAPHS AND BAYESIAN PRIORS

SciTech Connect

Safarzadeh, Mohammadtaher; Ferguson, Henry C.; Lu, Yu; Inami, Hanae; Somerville, Rachel S.

2015-01-10

We present a new technique for overcoming confusion noise in deep far-infrared Herschel space telescope images making use of prior information from shorter λ < 2 μm wavelengths. For the deepest images obtained by Herschel, the flux limit due to source confusion is about a factor of three brighter than the flux limit due to instrumental noise and (smooth) sky background. We have investigated the possibility of de-confusing simulated Herschel PACS 160 μm images by using strong Bayesian priors on the positions and weak priors on the flux of sources. We find the blended sources and group them together and simultaneously fit their fluxes. We derive the posterior probability distribution function of fluxes subject to these priors through Monte Carlo Markov Chain (MCMC) sampling by fitting the image. Assuming we can predict the FIR flux of sources based on the ultraviolet-optical part of their SEDs to within an order of magnitude, the simulations show that we can obtain reliable fluxes and uncertainties at least a factor of three fainter than the confusion noise limit of 3σ {sub c} = 2.7 mJy in our simulated PACS-160 image. This technique could in principle be used to mitigate the effects of source confusion in any situation where one has prior information of positions and plausible fluxes of blended sources. For Herschel, application of this technique will improve our ability to constrain the dust content in normal galaxies at high redshift.

9. The confusion effect when attacking simulated three-dimensional starling flocks

PubMed Central

Hildenbrandt, Hanno; Scott-Samuel, Nicholas E.; Cuthill, Innes C.; Hemelrijk, Charlotte K.

2017-01-01

The confusion effect describes the phenomenon of decreasing predator attack success with increasing prey group size. However, there is a paucity of research into the influence of this effect in coherent groups, such as flocks of European starlings (Sturnus vulgaris). Here, for the first time, we use a computer game style experiment to investigate the confusion effect in three dimensions. To date, computerized studies on the confusion effect have used two-dimensional simulations with simplistic prey movement and dynamics. Our experiment is the first investigation of the effects of flock size and density on the ability of a (human) predator to track and capture a target starling in a realistically simulated three-dimensional flock of starlings. In line with the predictions of the confusion effect, modelled starlings appear to be safer from predation in larger and denser flocks. This finding lends credence to previous suggestions that starling flocks have anti-predator benefits and, more generally, it suggests that active increases in density in animal groups in response to predation may increase the effectiveness of the confusion effect. PMID:28280553

10. [Functional imaging for brain tumors (perfusion, DTI and MR spectroscopy)].

PubMed

Essig, M; Giesel, F; Stieltjes, B; Weber, M A

2007-06-01

This contribution considers the possibilities involved with using functional methods in magnetic resonance imaging (MRI) diagnostics for brain tumors. Of the functional methods available, we discuss perfusion MRI (PWI), diffusion MRI (DWI and DTI) and MR spectroscopy (H-MRS). In cases of brain tumor, PWI aids in grading and better differentiation in diagnostics as well as for pre-therapeutic planning. In addition, the course of treatment, both after chemo- as well as radiotherapy in combination with surgical treatment, can be optimized. PWI allows better estimates of biological activity and aggressiveness in low grade brain tumors, and in the case of WHO grade II astrocytoma showing anaplasically transformed tumor areas, allows more rapid visu-alization and a better prediction of the course of the disease than conventional MRI diagnostics. Diffusion MRI, due to the directional dependence of the diffusion, can illustrate the course and direction of the nerve fibers, as well as reconstructing the nerve tracts in the cerebrum, pons and cerebellum 3-dimensionally. Diffusion imaging can be used for describing brain tumors, for evaluating contralateral involvement and the course of the nerve fibers near the tumor. Due to its operator dependence, DTI based fiber tracking for defining risk structures is controversial. DWI can also not differentiate accurately between cystic and necrotic brain tumors, or between metastases and brain abscesses. H-MRS provides information on cell membrane metabolism, neuronal integrity and the function of neuronal structures, energy metabolism and the formation of tumors and brain tissue necroses. Diagnostic problems such as the differentiation between neoplastic and non-neoplastic lesions, grading cerebral glioma and distinguishing between primary brain tumors and metastases can be resolved. An additional contribution will discuss the control of the course of glial tumors after radiotherapy.

11. Myocardial perfusion scintigraphy: the evidence

PubMed Central

Anagnostopoulos, C.; Cerqueira, M.; Ell, P. J.; Flint, E. J.; Harbinson, M.; Kelion, A. D.; Al-Mohammad, A.; Prvulovich, E. M.; Shaw, L. J.; Tweddel, A. C.

2003-01-01

This review summarises the evidence for the role of myocardial perfusion scintigraphy (MPS) in patients with known or suspected coronary artery disease. It is the product of a consensus conference organised by the British Cardiac Society, the British Nuclear Cardiology Society and the British Nuclear Medicine Society and is endorsed by the Royal College of Physicians of London and the Royal College of Radiologists. It was used to inform the UK National Institute of Clinical Excellence in their appraisal of MPS in patients with chest pain and myocardial infarction. MPS is a well-established, non-invasive imaging technique with a large body of evidence to support its effectiveness in the diagnosis and management of angina and myocardial infarction. It is more accurate than the exercise ECG in detecting myocardial ischaemia and it is the single most powerful technique for predicting future coronary events. The high diagnostic accuracy of MPS allows reliable risk stratification and guides the selection of patients for further interventions, such as revascularisation. This in turn allows more appropriate utilisation of resources, with the potential for both improved clinical outcomes and greater cost-effectiveness. Evidence from modelling and observational studies supports the enhanced cost-effectiveness associated with MPS use. In patients presenting with stable or acute chest pain, strategies of investigation involving MPS are more cost-effective than those not using the technique. MPS also has particular advantages over alternative techniques in the management of a number of patient subgroups, including women, the elderly and those with diabetes, and its use will have a favourable impact on cost-effectiveness in these groups. MPS is already an integral part of many clinical guidelines for the investigation and management of angina and myocardial infarction. However, the technique is underutilised in the UK, as judged by the inappropriately long waiting times and by

12. Cardiac tissue engineering using perfusion bioreactor systems

PubMed Central

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

13. Diffusion barriers

NASA Technical Reports Server (NTRS)

Nicolet, M. A.

1983-01-01

The choice of the metallic film for the contact to a semiconductor device is discussed. One way to try to stabilize a contact is by interposing a thin film of a material that has low diffusivity for the atoms in question. This thin film application is known as a diffusion barrier. Three types of barriers can be distinguished. The stuffed barrier derives its low atomic diffusivity to impurities that concentrate along the extended defects of a polycrystalline layer. Sacrificial barriers exploit the fact that some (elemental) thin films react in a laterally uniform and reproducible fashion. Sacrificial barriers have the advantage that the point of their failure is predictable. Passive barriers are those most closely approximating an ideal barrier. The most-studied case is that of sputtered TiN films. Stuffed barriers may be viewed as passive barriers whose low diffusivity material extends along the defects of the polycrystalline host.

NASA Technical Reports Server (NTRS)

1981-01-01

A diffuse celestial radiation which is isotropic at least on a course scale were measured from the soft X-ray region to about 150 MeV, at which energy the intensity falls below that of the galactic emission for most galactic latitudes. The spectral shape, the intensity, and the established degree of isotropy of this diffuse radiation already place severe constraints on the possible explanations for this radiation. Among the extragalactic theories, the more promising explanations of the isotropic diffuse emission appear to be radiation from exceptional galaxies from matter antimatter annihilation at the boundaries of superclusters of galaxies of matter and antimatter in baryon symmetric big bang models. Other possible sources for extragalactic diffuse gamma radiation are discussed and include normal galaxies, clusters of galaxies, primordial cosmic rays interacting with intergalactic matter, primordial black holes, and cosmic ray leakage from galaxies.

15. Synthesis and spectroscopy of a series of substituted N-confused tetraphenylporphyrins.

PubMed

Shaw, Janet L; Garrison, Shana A; Alemán, Elvin A; Ziegler, Christopher J; Modarelli, David A

2004-10-29

A series of N-confused tetraphenylporphyrins (H(2)NCTPPs) with substituents on either the para- or the 3,5-positions of the meso phenyl rings were prepared using Lindsey conditions. Both electron-withdrawing and electron-donating groups were chosen in order to probe the effects of peripheral substitution on the properties of the macrocycles. The series includes 5,10,15,20-tetra-(4-R-phenyl) N-confused porphyrins (where R = bromo (1), iodo (2), cyano (3), methoxy (4), 2',5'-dimethoxyphenyl (5), or ethynyl (6)) and 5,10,15,20-(3,5-di-tert-butylphenyl) N-confused porphyrin (7). Absorption and steady-state fluorescence measurements were carried out, and quantum yields were measured for all compounds in both dichloromethane (CH(2)Cl(2)) and dimethylacetamide (DMAc).

16. Imaging of myocardial perfusion with magnetic resonance.

PubMed

Barkhausen, Jörg; Hunold, Peter; Jochims, Markus; Debatin, Jörg F

2004-06-01

Coronary artery disease (CAD) is currently the leading cause of death in developed nations. Reflecting the complexity of cardiac function and morphology, noninvasive diagnosis of CAD represents a major challenge for medical imaging. Although coronary artery stenoses can be depicted with magnetic resonance (MR) and computed tomography (CT) techniques, its functional or hemodynamic impact frequently remains elusive. Therefore, there is growing interest in other, target organ-specific parameters such as myocardial function at stress and first-pass myocardial perfusion imaging to assess myocardial blood flow. This review explores the pathophysiologic background, recent technical developments, and current clinical status of first-pass MR imaging (MRI) of myocardial perfusion.

17. Distributions of perfusion and lung water.

PubMed

Ekeh, S U; Chu, R Y; Ficken, V J; Allen, E W; Ryals, C J

1990-01-01

We investigated the feasibility of using 123I-iodoantipyrine (123I-IAP) and 99mTc-labeled macroaggregated albumin (99mTc-MAA) to describe and compare the distributions of perfusion and water content in lung injuries. These radiopharmaceuticals were administered to 9 rabbits, 5 control and 4 with lung injuries. Isolated lungs were imaged by a scintillation gamma camera. The distribution of 123I-IAP outlined the entire lung mass whereas perfusion defect in the distribution of 99mTc-MAA was seen clearly in the case of severe lung injury.

18. Stress-first Myocardial Perfusion Imaging.

PubMed

Hussain, Nasir; Parker, Matthew W; Henzlova, Milena J; Duvall, William Lane

2016-02-01

Stress-first approaches to myocardial perfusion imaging provide diagnostically and prognostically accurate perfusion data equivalent to a full rest-stress study, save time in the imaging laboratory, and reduce the radiation exposure to patients and laboratory staff. Converting a nuclear cardiology laboratory from a conventional rest-stress strategy to a stress-first approach involves challenges such as the need for attenuation correction, triage of patients to an appropriate protocol, real-time review of stress images, and consideration of differential reimbursement. Copyright © 2016 Elsevier Inc. All rights reserved.

19. Metabolic Characteristics of Human Hearts Preserved for 12 Hours by Static Storage, Antegrade Perfusion or Retrograde Coronary Sinus Perfusion

PubMed Central

Cobert, Michael L.; Merritt, Matthew E.; West, LaShondra M.; Ayers, Colby; Jessen, Michael E.; Peltz, Matthias

2014-01-01

20. Meta-Analysis of Stress Myocardial Perfusion Imaging

ClinicalTrials.gov

2017-06-06

Coronary Disease; Echocardiography; Fractional Flow Reserve, Myocardial; Hemodynamics; Humans; Magnetic Resonance Imaging; Myocardial Perfusion Imaging; Perfusion; Predictive Value of Tests; Single Photon Emission Computed Tomography; Positron Emission Tomography; Multidetector Computed Tomography; Echocardiography, Stress; Coronary Angiography

1. Blood leakage and melphalan leakage from the perfusion circuit during regional hyperthermic perfusion for malignant melanoma

SciTech Connect

Hafstroem, L.; Hugander, A.; Joensson, P.E.; Westling, H.; Ehrsson, H.

1984-06-01

In regional hyperthermic perfusion with melphalan for patients with malignant melanoma of the leg, plasma leakage between the perfusion circuit and the systemic circulation was 4-7 ml X min-1. The melphalan concentration in the perfusate was biphasic, with half-lives of 8-12 mins for the initial phase and 19-28 mins for the second phase, after the first dose. After a second dose, the corresponding values were 11-13 and 26-34 mins. The highest concentration in general circulation was 0.38 micrograms X ml-1.

2. Characteristics of Patients Who Report Confusion After Reading Their Primary Care Clinic Notes Online.

PubMed

Root, Joseph; Oster, Natalia V; Jackson, Sara L; Mejilla, Roanne; Walker, Jan; Elmore, Joann G

2016-01-01

Patient access to online electronic medical records (EMRs) is increasing and may offer benefits to patients. However, the inherent complexity of medicine may cause confusion. We elucidate characteristics and health behaviors of patients who report confusion after reading their doctors' notes online. We analyzed data from 4,528 patients in Boston, MA, central Pennsylvania, and Seattle, WA, who were granted online access to their primary care doctors' clinic notes and who viewed at least one note during the 1-year intervention. Three percent of patients reported confusion after reading their visit notes. These patients were more likely to be at least 70 years of age (p < .0001), have fewer years of education (p < .0017), be unemployed (p < .0001), have lower levels of self-reported health (p < .0043), and worry more after reading visit notes (relative risk [RR] 4.83; confidence interval [CI] 3.17, 7.36) compared to patients who were not confused. In adjusted analyses, they were less likely to report feeling more in control of their health (RR 0.42; CI 0.25, 0.71), remembering their care plan (RR 0.26; CI 0.17, 0.42), and understanding their medical conditions (RR 0.32; CI 0.19, 0.54) as a result of reading their doctors' notes compared to patients who were not confused. Patients who were confused by reading their doctors' notes were less likely to report benefits in health behaviors. Understanding this small subset of patients is a critical step in reducing gaps in provider-patient communication and in efforts to tailor educational approaches for patients.

3. Intraocular lens confusions: a preventable "never event" - The Royal Victorian Eye and Ear Hospital protocol.

PubMed

Zamir, Ehud; Beresova-Creese, Katarina; Miln, Linda

2012-09-01

Intraocular lens (IOL) confusions and errors are among the most common postoperative adverse events. Errors may occur at any stage from the decision to operate to the insertion of the IOL. The most common errors occur during IOL selection pre-operative preparation (anaesthesia given before recognition that the intended IOL is not available), or intraoperatively (wrong IOL implanted because of confusion in the operating room). We review the mechanisms of errors reported in the literature and describe the experience at The Royal Victorian Eye and Ear Hospital. We also describe the implementation of an error-detection protocol and provide qualitative data on its performance.

4. Effects of laser acupuncture on blood perfusion rate

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. 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.

6. Perfusion MRI: The Five Most Frequently Asked Clinical Questions

PubMed Central

Essig, Marco; Nguyen, Thanh Binh; Shiroishi, Mark S.; Saake, Marc; Provenzale, James M.; Enterline, David S.; Anzalone, Nicoletta; Dörfler, Arnd; Rovira, Àlex; Wintermark, Max; Law, Meng

2013-01-01

OBJECTIVE This article addresses questions that radiologists frequently ask when planning, performing, processing, and interpreting MRI perfusion studies in CNS imaging. CONCLUSION Perfusion MRI is a promising tool in assessing stroke, brain tumors, and neurodegenerative diseases. Most of the impediments that have limited the use of perfusion MRI can be overcome to allow integration of these methods into modern neuroimaging protocols. PMID:23971482

7. Increased sinusoidal volume and solute extraction during retrograde liver perfusion

SciTech Connect

Bass, N.M.; Manning, J.A.; Weisiger, R.A.

1989-06-01

Retrograde isolated liver perfusion has been used to probe acinar functional heterogeneity, but the hemodynamic effects of backward flow have not been characterized. In this study, extraction of a long-chain fatty acid derivative, 12-N-methyl-7-nitrobenzo-2-oxa-1,3-diazol-amino stearate (12-NBDS), was greater during retrograde than during anterograde perfusion of isolated rat liver. To determine whether hemodynamic differences between anterograde and retrograde perfused livers could account for this finding, the hepatic extracellular space was measured for both directions of flow by means of (/sup 14/C)sucrose washout during perfusion as well as by direct measurement of (/sup 14/C)sucrose entrapped during perfusion. A three- to fourfold enlargement of the total hepatic extracellular space was found during retrograde perfusion by both approaches. Examination of perfusion-fixed livers by light microscopy and morphometry revealed that marked distension of the sinusoids occurred during retrograde perfusion and that this accounts for the observed increase in the (/sup 14/C)sucrose space. These findings support the hypothesis that maximum resistance to perfusate flow in the isolated perfused rat liver is located at the presinusoidal level. In addition, increased transit time of perfusate through the liver and greater sinusoidal surface area resulting from sinusoidal distension may account for the higher extraction of 12-NBDS and possibly other compounds by retrograde perfused liver.

8. An alternative method for neonatal cerebro-myocardial perfusion

PubMed Central

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

2012-01-01

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. PMID:22307393

9. Perfusion weighted imaging in the assessment of the pathology and outcomes of lateral medullary infarction

PubMed Central

Zhang, Dao P.; Zhang, Hong T.; Yin, Suo; Yan, Fu L.

2016-01-01

This series case report aimed to elucidate the underlying pathology and outcomes of lateral medullary infarction (LMI) using perfusion weighted imaging (PWI). Four patients were diagnosed with LMI based on high-field diffusion-weighted magnetic resonance imaging (MRI-DWI) and PWI. The national institutes of health stroke scale (NIHSS) scores were recorded on days 1, 7, and 30, and the Barthel index was assessed on days 7 and 30. Three patients exhibited relative regional hypoperfusion of medullary lesion in the perfusion maps. Two cases exhibited ipsilateral hypoperfusion in the inferior cerebellum, whereas one patient exhibited a relatively regional hyperperfusion in the medulla oblongata. The LMI patients with a high NIHSS score and low Barthel index on days 7 and 30 exhibited regional hypoperfusion. This report of 4 LMI cases provides preliminary evidence that regional hypoperfusion may contribute to worse outcomes in LMI. PMID:27744467

10. Diffuser Test

NASA Image and Video Library

2007-09-13

Tests begun at Stennis Space Center's E Complex Sept. 13 evaluated a liquid oxygen lead for engine start performance, part of the A-3 Test Facility Subscale Diffuser Risk Mitigation Project at SSC's E-3 Test Facility. Phase 1 of the subscale diffuser project, completed Sept. 24, was a series of 18 hot-fire tests using a 1,000-pound liquid oxygen and gaseous hydrogen thruster to verify maximum duration and repeatability for steam generation supporting the A-3 Test Stand project. The thruster is a stand-in for NASA's developing J-2X engine, to validate a 6 percent scale version of A-3's exhaust diffuser. Testing the J-2X at altitude conditions requires an enormous diffuser. Engineers will generate nearly 4,600 pounds per second of steam to reduce pressure inside A-3's test cell to simulate altitude conditions. A-3's exhaust diffuser has to be able to withstand regulated pressure, temperatures and the safe discharge of the steam produced during those tests. Before the real thing is built, engineers hope to work out any issues on the miniature version. Phase 2 testing is scheduled to begin this month.

11. Impact of image denoising on image quality, quantitative parameters and sensitivity of ultra-low-dose volume perfusion CT imaging.

PubMed

Othman, Ahmed E; Brockmann, Carolin; Yang, Zepa; Kim, Changwon; Afat, Saif; Pjontek, Rastislav; Nikoubashman, Omid; Brockmann, Marc A; Nikolaou, Konstantin; Wiesmann, Martin; Kim, Jong Hyo

2016-01-01

To examine the impact of denoising on ultra-low-dose volume perfusion CT (ULD-VPCT) imaging in acute stroke. Simulated ULD-VPCT data sets at 20 % dose rate were generated from perfusion data sets of 20 patients with suspected ischemic stroke acquired at 80 kVp/180 mAs. Four data sets were generated from each ULD-VPCT data set: not-denoised (ND); denoised using spatiotemporal filter (D1); denoised using quanta-stream diffusion technique (D2); combination of both methods (D1 + D2). Signal-to-noise ratio (SNR) was measured in the resulting 100 data sets. Image quality, presence/absence of ischemic lesions, CBV and CBF scores according to a modified ASPECTS score were assessed by two blinded readers. SNR and qualitative scores were highest for D1 + D2 and lowest for ND (all p ≤ 0.001). In 25 % of the patients, ND maps were not assessable and therefore excluded from further analyses. Compared to original data sets, in D2 and D1 + D2, readers correctly identified all patients with ischemic lesions (sensitivity 1.0, kappa 1.0). Lesion size was most accurately estimated for D1 + D2 with a sensitivity of 1.0 (CBV) and 0.94 (CBF) and an inter-rater agreement of 1.0 and 0.92, respectively. An appropriate combination of denoising techniques applied in ULD-VPCT produces diagnostically sufficient perfusion maps at substantially reduced dose rates as low as 20 % of the normal scan. Perfusion-CT is an accurate tool for the detection of brain ischemias. The high associated radiation doses are a major drawback of brain perfusion CT. Decreasing tube current in perfusion CT increases image noise and deteriorates image quality. Combination of different image-denoising techniques produces sufficient image quality from ultra-low-dose perfusion CT.

12. Vibration-response imaging versus quantitative perfusion scintigraphy in the selection of patients for lung-resection surgery.

PubMed

Comce, Fatma; Bingol, Zuleyha; Kiyan, Esen; Tanju, Serhan; Toker, Alper; Cagatay, Pembe; Ece, Turhan

2011-12-01

In patients being considered for lung-resection surgery, quantitative perfusion scintigraphy is used to predict postoperative lung function and guide the determination of lung-resection candidacy. Vibration-response imaging has been proposed as a noninvasive, radiation-free, and simpler method to predict postoperative lung function. We compared vibration-response imaging to quantitative perfusion scintigraphy for predicting postoperative FEV(1) and diffusing capacity of the lung for carbon monoxide (D(LCO)). We enrolled 35 candidates for lung resection. Twenty-five patients had preoperative FEV(1) and D(LCO) MEASUREMENTS: The vibration-response-imaging measurements showed strong correlation with the quantitative-perfusion-scintigraphy measurements of predicted postoperative FEV(1)% (r = 0.87, P < .001), predicted postoperative FEV(1) (r = 0.90, P < .001), and predicted postoperative D(LCO)% (r = 0.90, P < .001). There was a correlation between predicted postoperative FEV(1) (% and L) measured via quantitative perfusion scintigraphy and the actual postoperative FEV(1) (% and L) (r = 0.47, P = .048, r = 0.73, P < .001). There was no difference between the vibration-response-imaging measurements and the actual postoperative measurements of predicted postoperative FEV(1) (% and L). There was a correlation between predicted postoperative FEV(1) (% and L) measured via vibration-response imaging and actual postoperative FEV(1) (% and L) (r = 0.52, P = .044, r = 0.79, P < .001). The mean differences between the predicted and actual postoperative FEV(1) values were 49 mL with vibration-response imaging, versus 230 mL with quantitative perfusion scintigraphy. Neither the vibration-response imaging nor the quantitative perfusion scintigraphy predicted postoperative D(LCO)% values agreed with the actual postoperative D(LCO)% values. Vibration-response imaging may be a good alternative to quantitative perfusion scintigraphy in evaluating lung-resection candidacy.

13. Lung Perfusion Scanning in Hepatic Cirrhosis

PubMed Central

Stanley, N. N.; Ackrill, P.; Wood, J.

1972-01-01

Abnormal lung perfusion scans using radioactive particles were found in five out of six cases of hepatic cirrhosis with arterial hypoxaemia. None had clinical evidence of cardiopulmonary disease or signs of pulmonary embolism on arteriography. The scan defects are probably caused by a disorder of the pulmonary microvasculature, which may show regional variation in severity. ImagesFIG. 1FIG. 2 PMID:4645896

14. A reappraisal of retrograde cerebral perfusion

PubMed Central

2013-01-01

Brain protection during aortic arch surgery by perfusing cold oxygenated blood into the superior vena cava was first reported by Lemole et al. In 1990 Ueda and associates first described the routine use of continuous retrograde cerebral perfusion (RCP) in thoracic aortic surgery for the purpose of cerebral protection during the interval of obligatory interruption of anterograde cerebral flow. The beneficial effects of RCP may be its ability to sustain brain hypothermia during hypothermic circulatory arrest (HCA) and removal of embolic material from the arterial circulation of the brain. RCP can offer effective brain protection during HCA for about 40 to 60 minutes. Animal experiments revealed that RCP provided inadequate cerebral perfusion and that neurological recovery was improved with selective antegrade cerebral perfusion (ACP), however, both RCP and ACP provide comparable clinical outcomes regarding both the mortality and stroke rates by risk-adjusted and case-matched comparative study. RCP still remains a valuable adjunct for brain protection during aortic arch repair in particular pathologies and patients. PMID:23977600

15. 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.

16. 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.

17. Coupling between resting cerebral perfusion and EEG.

PubMed

O'Gorman, R L; Poil, S-S; Brandeis, D; Klaver, P; Bollmann, S; Ghisleni, C; Lüchinger, R; Martin, E; Shankaranarayanan, A; Alsop, D C; Michels, L

2013-07-01

While several studies have investigated interactions between the electroencephalography (EEG) and functional magnetic resonance imaging BOLD signal fluctuations, less is known about the associations between EEG oscillations and baseline brain haemodynamics, and few studies have examined the link between EEG power outside the alpha band and baseline perfusion. Here we compare whole-brain arterial spin labelling perfusion MRI and EEG in a group of healthy adults (n = 16, ten females, median age: 27 years, range 21-48) during an eyes closed rest condition. Correlations emerged between perfusion and global average EEG power in low (delta: 2-4 Hz and theta: 4-7 Hz), middle (alpha: 8-13 Hz), and high (beta: 13-30 Hz and gamma: 30-45 Hz) frequency bands in both cortical and sub-cortical regions. The correlations were predominately positive in middle and high-frequency bands, and negative in delta. In addition, central alpha frequency positively correlated with perfusion in a network of brain regions associated with the modulation of attention and preparedness for external input, and central theta frequency correlated negatively with a widespread network of cortical regions. These results indicate that the coupling between average EEG power/frequency and local cerebral blood flow varies in a frequency specific manner. Our results are consistent with longstanding concepts that decreasing EEG frequencies which in general map onto decreasing levels of activation.

18. Asynchronicity of Facial Blood Perfusion in Migraine

PubMed Central

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

19. Defining acute ischemic stroke tissue pathophysiology with whole brain CT perfusion.

PubMed

Bivard, A; Levi, C; Krishnamurthy, V; Hislop-Jambrich, J; Salazar, P; Jackson, B; Davis, S; Parsons, M

2014-12-01

This study aimed to identify and validate whole brain perfusion computed tomography (CTP) thresholds for ischemic core and salvageable penumbra in acute stroke patients and develop a probability based model to increase the accuracy of tissue pathophysiology measurements. One hundred and eighty-three patients underwent multimodal stroke CT using a 320-slice scanner within 6hours of acute stroke onset, followed by 24hour MRI that included diffusion weighted imaging (DWI) and dynamic susceptibility weighted perfusion imaging (PWI). Coregistered acute CTP and 24hour DWI was used to identify the optimum single perfusion parameter thresholds to define penumbra (in patients without reperfusion), and ischemic core (in patients with reperfusion), using a pixel based receiver operator curve analysis. Then, these results were used to develop a sigma curve fitted probability based model incorporating multiple perfusion parameter thresholds. For single perfusion thresholds, a time to peak (TTP) of +5seconds best defined the penumbra (area under the curve, AUC 0.79 CI 0.74-0.83) while a cerebral blood flow (CBF) of < 50% best defined the acute ischemic core (AUC 0.73, CI 0.69-0.77). The probability model was more accurate at detecting the ischemic core (AUC 0.80 SD 0.75-0.83) and penumbra (0.85 SD 0.83-0.87) and was significantly closer in volume to the corresponding reference DWI (P=0.031). Whole brain CTP can accurately identify penumbra and ischemic core using similar thresholds to previously validated 16 or 64 slice CTP. Additionally, a novel probability based model was closer to defining the ischemic core and penumbra than single thresholds. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

20. Modeling Intragranular Diffusion in Low-Connectivity Granular Media

SciTech Connect

Ewing, Robert G.; Liu, Chongxuan; Hu, Qinhong

2012-03-20

Diffusive exchange of solutes between bulk water in an aquifer and water in the intragranular pores of the solid phase remains confusing after decades of study. In a previous paper, we reviewed some of the explanations, and suggested that the disparities between observation and theory were largely due to low connectivity of the intragranular pores. Low connectivity indicates that a useful conceptual framework is percolation theory, which guided our analysis. The present study was initiated to improve the finite difference (FD) model presented in the previous paper, and to test that new model rigorously against new random walk (RW) simulations of diffusion in low-connectivity porous spheres starting from non-equilibrium. The new FD model calculates diffusion separately in the infinite cluster and the finite clusters, and closely matches the new, more complex RW results. The percolation-theory based description of the new model is fairly simple, and can readily be incorporated into existing FD models. The simulations showed that the combination of low intragranular pore connectivity, and out-diffusion initiated at diffusive non-equilibrium, can produce diffusive behavior that appears as if the solute had undergone slow sorption, even in the absence of any sorption process. This mechanism may help explain some hitherto confusing aspects of intragranular diffusion.

1. Volume perfusion CT imaging of cerebral vasospasm: diagnostic performance of different perfusion maps.

PubMed

Othman, Ahmed E; Afat, Saif; Nikoubashman, Omid; Müller, Marguerite; Schubert, Gerrit Alexander; Bier, Georg; Brockmann, Marc A; Wiesmann, Martin; Brockmann, Carolin

2016-08-01

In this study, we aimed to evaluate the diagnostic performance of different volume perfusion CT (VPCT) maps regarding the detection of cerebral vasospasm compared to angiographic findings. Forty-one datasets of 26 patients (57.5 ± 10.8 years, 18 F) with subarachnoid hemorrhage and suspected cerebral vasospasm, who underwent VPCT and angiography within 6 h, were included. Two neuroradiologists independently evaluated the presence and severity of vasospasm on perfusion maps on a 3-point Likert scale (0-no vasospasm, 1-vasospasm affecting <50 %, 2-vasospasm affecting >50 % of vascular territory). A third neuroradiologist independently assessed angiography for the presence and severity of vasospasm on a 3-point Likert scale (0-no vasospasm, 1-vasospasm affecting < 50 %, 2-vasospasm affecting > 50 % of vessel diameter). Perfusion maps of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time to drain (TTD) were evaluated regarding diagnostic accuracy for cerebral vasospasm with angiography as reference standard. Correlation analysis of vasospasm severity on perfusion maps and angiographic images was performed. Furthermore, inter-reader agreement was assessed regarding findings on perfusion maps. Diagnostic accuracy for TTD and MTT was significantly higher than for all other perfusion maps (TTD, AUC = 0.832; MTT, AUC = 0.791; p < 0.001). TTD revealed higher sensitivity than MTT (p = 0.007). The severity of vasospasm on TTD maps showed significantly higher correlation levels with angiography than all other perfusion maps (p ≤ 0.048). Inter-reader agreement was (almost) perfect for all perfusion maps (kappa ≥ 0.927). The results of this study indicate that TTD maps have the highest sensitivity for the detection of cerebral vasospasm and highest correlation with angiography regarding the severity of vasospasm.

2. Optimal pulmonary artery perfusion mode and perfusion pressure during cardiopulmonary bypass.

PubMed

Zhang, R; Wang, Z; Wang, H; Song, H; Zhang, N; Fang, M

2010-06-01

Reducing lung injury during cardiopulmonary bypass (CPB) is important for patients' recovery. The present study was designed to evaluate the effects of pulmonary artery perfusion pressure on the extent of lung injury during CPB in an animal model. Twenty healthy mongrel dogs were randomly divided into four groups, including a control group and three perfusion groups designed to simulate clinical cardiopulmonary bypass-induced lung injury. During pulmonary ischemia and cardiopulmonary bypass, protective perfusions were performed using different perfusion pressures (15-20, 25-30, and 40-45 mmHg), while animals in the control group were not perfused. After pulmonary reperfusion, the changes in pulmonary function and tissue histopathology were determined. Compared with the control group, lung compliance, oxygenation and vascular resistance after reperfusion were significantly improved in both low- and moderate-pressure groups. The malonaldehyde concentration, neutrophil sequestration ratio, and expression of ICAM-1 were also decreased significantly in the two groups. However, there were no significant differences in any of these parameters between the control group and the high-pressure group. Histopathological examination demonstrated that there were obvious inflammatory cell infiltration and tissue damage in the control and high-pressure groups, which was prevented in the low- and moderate-pressure groups. The perfusion pressure is an important factor that determines the extent of lung protection, and the use of pressures below 30 mmHg is optimal, with the safest and most effective range being 15-20 mmHg.

3. The Perfusion Downunder collaborative database project.

PubMed

Newland, Richard; Baker, Robert A; Stanley, Rebecca; Place, Katherine; Willcox, Timothy W

2008-09-01

The Perfusion Downunder Collaboration provides research infrastructure and support to the Australian and New Zealand perfusion community, with the objective of determining best practices and producing relevant research publications. The Perfusion Downunder Collaborative Database (PDUCD) has been created for the purpose of collecting a dataset for cardiopulmonary bypass (CPB) procedures that includes integration with commercially available CPB data collection software. Initial testing of the PDUCD involved collection of data from four Australian and New Zealand hospitals from March to July 2007. Data from 513 procedures were compared with the concurrent Australasian Society of Cardiac and Thoracic Surgeons (ASCTS) database report to assess the validity of the collected data. Demographic, preoperative, and procedural variables were comparable between databases. Perfusion variables showed a median nasopharyngeal temperature of 36.7degrees C at separation from CPB (range, 35.3-37.5 degrees C), which was similar to maximum nasopharyngeal temperature (median, 36.8 degrees C). Median arterial flow and mean arterial pressure were 4.2 L/min and 57.2 mmHg, respectively. Control charts indicate a central tendency of 12.5 minutes for mean arterial pressure < 50 mmHg and 3.5 minutes for arterial flow < 1.6 L/min/m2 (cumulative time). There was no difference in median minimum and maximum blood glucose between diabetic and nondiabetic patients during CPB with 40% of patients receiving insulin. Median minimum and maximum activated clotting time (ACT) during CPB was 581 and 692 seconds, respectively. Outcome data for isolated coronary artery bypass grafting were similar for mortality (only) (both 1.8%). Initial data collection showed concurrent validity compared with the ASCTS database. The inclusion of a large quantity of calculated CPB variables in the dataset highlights the benefits of electronic data collection as a research tool within a collaborative research network and the

4. Ventilation-perfusion distribution in normal subjects.

PubMed

Beck, Kenneth C; Johnson, Bruce D; Olson, Thomas P; Wilson, Theodore A

2012-09-01

Functional values of LogSD of the ventilation distribution (σ(V)) have been reported previously, but functional values of LogSD of the perfusion distribution (σ(q)) and the coefficient of correlation between ventilation and perfusion (ρ) have not been measured in humans. Here, we report values for σ(V), σ(q), and ρ obtained from wash-in data for three gases, helium and two soluble gases, acetylene and dimethyl ether. Normal subjects inspired gas containing the test gases, and the concentrations of the gases at end-expiration during the first 10 breaths were measured with the subjects at rest and at increasing levels of exercise. The regional distribution of ventilation and perfusion was described by a bivariate log-normal distribution with parameters σ(V), σ(q), and ρ, and these parameters were evaluated by matching the values of expired gas concentrations calculated for this distribution to the measured values. Values of cardiac output and LogSD ventilation/perfusion (Va/Q) were obtained. At rest, σ(q) is high (1.08 ± 0.12). With the onset of ventilation, σ(q) decreases to 0.85 ± 0.09 but remains higher than σ(V) (0.43 ± 0.09) at all exercise levels. Rho increases to 0.87 ± 0.07, and the value of LogSD Va/Q for light and moderate exercise is primarily the result of the difference between the magnitudes of σ(q) and σ(V). With known values for the parameters, the bivariate distribution describes the comprehensive distribution of ventilation and perfusion that underlies the distribution of the Va/Q ratio.

5. Compounding Confusion? When Illustrative Practical Work Falls Short of Its Purpose--A Case Study

ERIC Educational Resources Information Center

Haigh, Mavis; France, Beverley; Gounder, Roshni

2012-01-01

Illustrative practical work is commonly used in chemistry education to enrich students' understandings of chemical phenomena. However, it is possible that such practical work may not serve to foster understanding but rather cause further confusion. This paper reports the struggles experienced by a group of senior (Year 12) secondary chemistry…

6. Repetition, Confusion and Surprise: A Stylistics Based Approach to Teaching Poetry in EFL Classrooms.

ERIC Educational Resources Information Center

Kingwell, Gail

A stylistics-based approach to teaching poetry in the English as a foreign language classroom is examined. Since students may not have the linguistic skills to appreciate a poem, an analytical framework is proposed that includes the elements of repetition, confusion, and surprise. Reference is made to two poems, "In a Season of Unemployment"…

7. Perception and Confusion of Speech Sounds by Adults with a Cochlear Implant

ERIC Educational Resources Information Center

Rodvik, Arne K.

2008-01-01

The aim of this pilot study was to identify the most common speech sound confusions of 5 Norwegian cochlear implanted post-lingually deafened adults. We played recorded nonwords, aCa, iCi and bVb, to our informants, asked them to repeat what they heard, recorded their repetitions and transcribed these phonetically. We arranged the collected data…

8. Teaching Database Modeling and Design: Areas of Confusion and Helpful Hints

ERIC Educational Resources Information Center

Philip, George C.

2007-01-01

This paper identifies several areas of database modeling and design that have been problematic for students and even are likely to confuse faculty. Major contributing factors are the lack of clarity and inaccuracies that persist in the presentation of some basic database concepts in textbooks. The paper analyzes the problems and discusses ways to…

9. Perception and Confusion of Speech Sounds by Adults with a Cochlear Implant

ERIC Educational Resources Information Center

Rodvik, Arne K.

2008-01-01

The aim of this pilot study was to identify the most common speech sound confusions of 5 Norwegian cochlear implanted post-lingually deafened adults. We played recorded nonwords, aCa, iCi and bVb, to our informants, asked them to repeat what they heard, recorded their repetitions and transcribed these phonetically. We arranged the collected data…

10. The use of Functional Consequences Theory in acutely confused hospitalized elderly.

PubMed

Kozak-Campbell, C; Hughes, A M

1996-01-01

Acute confusion is a common complication of hospitalization in the elderly that impacts on both the use of health care resources and the functional status of individuals. Providing optimum nursing care for these patients depends on three factors: 1) the nurse's ability to differentiate acute confusion from other common conditions in the hospitalized elderly, chiefly dementia or depression, 2) the nurse's ability to identify factors contributing to this condition, and 3) the implementation of interventions to minimize the effects of these factors on the patient. This article differentiates the clinical features of acute confusion from those of depression and dementia, and discusses the use of the Functional Consequences Theory, developed by Miller (1990), as a framework for nursing assessment and management of care for elderly patients with this condition. The functional consequences theory framework assists the nurse to identify risk factors associated with the development of acute confusion in the hospitalized elderly. Further it guides the development of interventions to minimize the effects of this condition in this population. The use of this framework in the clinical setting is illustrated through a case study.

11. The Susceptibility of Young Preschoolers to Source Similarity Effects: Confusing Story or Video Events with Reality

ERIC Educational Resources Information Center

Thierry, Karen L.; Pipe, Margaret-Ellen

2009-01-01

This study examined children's tendency to confuse events that varied in source similarity, which was manipulated using different media of event presentation. In Experiment 1, children in two age groups (3- and 4-year-olds and 5- and 6-year-olds) experienced a live presentation of an event, and another event was either heard from a story (low…

12. Vowel Confusion Patterns in Adults during Initial 4 Years of Implant Use

ERIC Educational Resources Information Center

Vaalimaa, Taina T.; Sorri, Martti J.; Laitakari, Jaakko; Sivonen, Ville; Muhli, Arto

2011-01-01

This study investigated adult cochlear implant users' (n == 39) vowel recognition and confusions by an open-set syllable test during 4 years of implant use, in a prospective repeated-measures design. Subjects' responses were coded for phoneme errors and estimated by the generalized mixed model. Improvement in overall vowel recognition was highest…

13. It Was the Most Confusing To Read; It Became Easier To Understand.

ERIC Educational Resources Information Center

Lambert, Michele

1999-01-01

Describes a writing assignment in which students read only the first two paragraphs of Charles Dickens's novel "A Tale of Two Cities" and then, after some brainstorming and prewriting, write a paragraph or two modeled on those, explaining the confusion and turmoil of the present day. Notes how Dickens's expressions become more familiar…

14. Mirror-Image Confusions: Implications for Representation and Processing of Object Orientation

ERIC Educational Resources Information Center

Gregory, Emma; McCloskey, Michael

2010-01-01

Perceiving the orientation of objects is important for interacting with the world, yet little is known about the mental representation or processing of object orientation information. The tendency of humans and other species to confuse mirror images provides a potential clue. However, the appropriate characterization of this phenomenon is not…

15. Mental Rotation Does Not Account for Sex Differences in Left-Right Confusion

ERIC Educational Resources Information Center

Ocklenburg, Sebastian; Hirnstein, Marco; Ohmann, Hanno Andreas; Hausmann, Markus

2011-01-01

Several studies have demonstrated that women believe they are more prone to left-right confusion (LRC) than men. However, while some studies report that there is also a sex difference in LRC tasks favouring men, others report that men and women perform equally well. Recently, it was suggested that sex differences only emerge in LRC tasks when they…

16. Energy and the Confused Student IV: A Global Approach to Energy

ERIC Educational Resources Information Center

Jewett, John W., Jr.

2008-01-01

Energy is a critical concept in physics problem-solving, but is often a major source of confusion for students if the presentation is not carefully crafted by the instructor or the textbook. In the first three articles in this series we discussed several issues related to the teaching of energy concepts. We have saved a major single issue for this…

17. Energy and the Confused Student IV: A Global Approach to Energy

ERIC Educational Resources Information Center

Jewett, John W., Jr.

2008-01-01

Energy is a critical concept in physics problem-solving, but is often a major source of confusion for students if the presentation is not carefully crafted by the instructor or the textbook. In the first three articles in this series we discussed several issues related to the teaching of energy concepts. We have saved a major single issue for this…

18. Psychometric properties of the Flemish translation of the NEECHAM Confusion Scale.

PubMed

Milisen, Koen; Foreman, Marquis D; Hendrickx, Annik; Godderis, Jan; Abraham, Ivo L; Broos, Paul L O; De Geest, Sabina

2005-03-25

Determination of a patient's cognitive status by use of a valid and reliable screening instrument is of major importance as early recognition and accurate diagnosis of delirium is necessary for effective management. This study determined the reliability, validity and diagnostic value of the Flemish translation of the NEECHAM Confusion Scale. A sample of 54 elderly hip fracture patients with a mean age of 80.9 years (SD = 7.85) were included. To test the psychometric properties of the NEECHAM Confusion Scale, performance on the NEECHAM was compared to the Confusion Assessment Method (CAM) and the Mini-Mental State Examination (MMSE), by using aggregated data based on 5 data collection measurement points (repeated measures). The CAM and MMSE served as gold standards. The alpha coefficient for the total NEECHAM score was high (0.88). Principal components analysis yielded a two-component solution accounting for 70.8% of the total variance. High correlations were found between the total NEECHAM scores and total MMSE (0.75) and total CAM severity scores (-0.73), respectively. Diagnostic values using the CAM algorithm as gold standard showed 76.9% sensitivity, 64.6% specificity, 13.5% positive and 97.5% negative predictive values, respectively. This validation of the Flemish version of the NEECHAM Confusion Scale adds to previous evidence suggesting that this scale holds promise as a valuable screening instrument for delirium in clinical practice. Further validation studies in diverse clinical populations; however, are needed.

19. Straw Men and False Dichotomies: Overcoming Philosophical Confusion in Chemical Education

ERIC Educational Resources Information Center

Taber, Keith S.

2010-01-01

Constructivism has been widely considered the most influential perspective in science education research for some decades, and has been the basis of widespread pedagogic advice in many educational contexts. Yet it has been claimed in this "Journal" that the philosophical basis of constructivist thought in chemical education is confused, and…

20. Molecular techniques for detection of confused flour beetle infestations in stored products

USDA-ARS?s Scientific Manuscript database

Tribolium confusum (confused flour beetle) is a stored-product pest which contaminates a wide range of food products, from flour and cereals to spices. The insect reduces food quality and is responsible for large economic losses every year. Although a number of methods for detection of stored-produc...

1. Compounding Confusion? When Illustrative Practical Work Falls Short of Its Purpose--A Case Study

ERIC Educational Resources Information Center

Haigh, Mavis; France, Beverley; Gounder, Roshni

2012-01-01

Illustrative practical work is commonly used in chemistry education to enrich students' understandings of chemical phenomena. However, it is possible that such practical work may not serve to foster understanding but rather cause further confusion. This paper reports the struggles experienced by a group of senior (Year 12) secondary chemistry…

2. The quadratus lumborum muscle: a possible source of confusion in sonographic evaluation of the retroperitoneum.

PubMed

Callen, P W; Filly, R A; Marks, W M

1979-10-01

The quadratus lumborum muscle has been noted to appear as a hypoechoic structure on sonograms of the abdomen. On occasion its appearance may simulate a pathologic fluid collection such as an abscess or retroperitoneal hematoma. Illustrative examples of this confusing appearance, as well as ways of avoiding this potential pitfall, are presented.

3. Delictual Negligence of Educators in Schools: The Confusing Influence of the "in loco parentis" Doctrine

ERIC Educational Resources Information Center

Potgieter, Johan

2004-01-01

This article points out that the "in loco parentis" maxim is partly to blame for introducing the confusing "reasonable parent" doctrine as the test for delictual negligence of educators in the school context. It is argued that the standard of care exercised by parents over their children is not appropriate to determine the negligence of educators.…

4. Learning Concepts in Social Studies: "Religion" as an Example of Conceptual Confusion.

ERIC Educational Resources Information Center

Allen, Rodney F.; Landry, Russell N.

1981-01-01

Reviews responses of 30 eighth grade social studies students and 30 11th grade history students to a request that they write a definition of religion. The mass confusion indicated in the responses is intended as a reminder to social studies teachers to define concepts in the context of their use. (DB)

5. Straw Men and False Dichotomies: Overcoming Philosophical Confusion in Chemical Education

ERIC Educational Resources Information Center

Taber, Keith S.

2010-01-01

Constructivism has been widely considered the most influential perspective in science education research for some decades, and has been the basis of widespread pedagogic advice in many educational contexts. Yet it has been claimed in this "Journal" that the philosophical basis of constructivist thought in chemical education is confused, and…

6. Mirror-Image Confusions: Implications for Representation and Processing of Object Orientation

ERIC Educational Resources Information Center

Gregory, Emma; McCloskey, Michael

2010-01-01

Perceiving the orientation of objects is important for interacting with the world, yet little is known about the mental representation or processing of object orientation information. The tendency of humans and other species to confuse mirror images provides a potential clue. However, the appropriate characterization of this phenomenon is not…

7. Repetition, Confusion and Surprise: A Stylistics Based Approach to Teaching Poetry in EFL Classrooms.

ERIC Educational Resources Information Center

Kingwell, Gail

A stylistics-based approach to teaching poetry in the English as a foreign language classroom is examined. Since students may not have the linguistic skills to appreciate a poem, an analytical framework is proposed that includes the elements of repetition, confusion, and surprise. Reference is made to two poems, "In a Season of Unemployment"…

8. Confusing Aspects in the Calculation of the Electrostatic Potential of an Infinite Line of Charge

ERIC Educational Resources Information Center

Jimenez, J. L.; Campos, I.; Roa-Neri, J. A. E.

2012-01-01

In this work we discuss the trick of eliminating infinite potential of reference arguing that it corresponds to a constant of integration, in the problem of determining the electrostatic potential of an infinite line of charge with uniform density, and show how the problem must be tackled properly. The usual procedure is confusing for most…

9. Teaching Database Modeling and Design: Areas of Confusion and Helpful Hints

ERIC Educational Resources Information Center

Philip, George C.

2007-01-01

This paper identifies several areas of database modeling and design that have been problematic for students and even are likely to confuse faculty. Major contributing factors are the lack of clarity and inaccuracies that persist in the presentation of some basic database concepts in textbooks. The paper analyzes the problems and discusses ways to…

10. Vowel Confusion Patterns in Adults during Initial 4 Years of Implant Use

ERIC Educational Resources Information Center

Vaalimaa, Taina T.; Sorri, Martti J.; Laitakari, Jaakko; Sivonen, Ville; Muhli, Arto

2011-01-01

This study investigated adult cochlear implant users' (n == 39) vowel recognition and confusions by an open-set syllable test during 4 years of implant use, in a prospective repeated-measures design. Subjects' responses were coded for phoneme errors and estimated by the generalized mixed model. Improvement in overall vowel recognition was highest…

11. Distractor onset but not preparation time affects the frequency of task confusions in task switching

PubMed Central

2015-01-01

12. It Was the Most Confusing To Read; It Became Easier To Understand.

ERIC Educational Resources Information Center

Lambert, Michele

1999-01-01

Describes a writing assignment in which students read only the first two paragraphs of Charles Dickens's novel "A Tale of Two Cities" and then, after some brainstorming and prewriting, write a paragraph or two modeled on those, explaining the confusion and turmoil of the present day. Notes how Dickens's expressions become more familiar…

13. Confusing Aspects in the Calculation of the Electrostatic Potential of an Infinite Line of Charge

ERIC Educational Resources Information Center

Jimenez, J. L.; Campos, I.; Roa-Neri, J. A. E.

2012-01-01

In this work we discuss the trick of eliminating infinite potential of reference arguing that it corresponds to a constant of integration, in the problem of determining the electrostatic potential of an infinite line of charge with uniform density, and show how the problem must be tackled properly. The usual procedure is confusing for most…

14. The Treatment of Six Sigma in Introductory Operations Management Textbooks: Clearing Up the Confusion

ERIC Educational Resources Information Center

Ravinder, Handanhal; Misra, Ram B.

2016-01-01

This paper critically examines the treatment of the statistical basis for Six Sigma and process capability in popular operations management textbooks. It discusses areas of confusion and suggest ways of treating the topic that make sense to instructors as well as students. Even though Six Sigma was introduced almost 30 years ago, misconceptions…

15. The development of a bioreactor to perfuse radially-confined hydrogel constructs: design and characterization of mass transport properties.

PubMed

Eniwumide, Joshua O; Lee, David A; Bader, Dan L

2009-01-01

Limitations to nutrient transport provide a challenge to the development of 3D tissue-engineered constructs. A heterogeneous distribution of viable cells and functional matrix within the developing tissue is a common consequence. In the present study, a bioreactor was developed to perfuse fluid through cylindrical agarose constructs. The transport and distribution of dextran molecules (FD-4, FD-500, FD-2000) within the agarose was visualized in order to determine the bioreactors effectiveness for transport enhancement. By 24 h, the perfusion bioreactor achieved 529%, 395% and 294% higher concentrations of FD-4, FD-500 and FD-2000, respectively, than those solely due to diffusion. Of particular interest was the effectiveness of the bioreactor to transport molecules to the central region of the constructs. In this respect, the perfusion bioreactor was found to increase transportation of FD-4, FD-500 and FD-2000 by 30%, 291% and 222% over that of diffusion. Articular chondrocytes were cultured and perfused using the bioreactor. The improved molecular transport achieved led to an average 75% and 1340% increase of DNA and sulphated GAG, respectively at 20 days. More significantly was the 106% and 1603% increase of DNA and GAG, respectively, achieved at the central core of the 3D constructs.

16. Transformations of N-confused porphyrin triggered by insertion of silicon(IV).

PubMed

Skonieczny, Janusz; Latos-Grazyński, Lechosław; Szterenberg, Ludmiła

2009-08-03

N-confused porphyrin, 5,10,15,20-tetraaryl-2-aza-21-carbaporphyrin, dissolved in triethylamine reacts with dichloromethylsilane yielding the methylsilicon(IV) complex of 5,10,15,20-tetraaryl-2-aza-21-hydroxy-21-carbaporphyrin. Addition of aldehydes or ketones (acetone, acetaldehyde acetophenone, butanone, propanal, benzaldehyde, p-methylbenzaldehyde, p-methoxybenzaldehyde, terephthaldehyde) into the insertion mixture triggered the profound transformation of N-confused porphyrin to form the methylsilicon(IV) complex of N-fused porphyrin derivative substituted at the inner C(9) position by a hydroxyalkyl moiety derived from aldehyde or ketone. The macrocyle is structurally related to an aromatic N-fused inner phlorin while the coordination polyhedron of bound silicon resembles the trigonal bipyramid. The macrocyclic ligand coordinates in the facial mode as the three pyrrolic nitrogen donors lie at the vertices of the single trigonal face. The meridional positions of the trigonal bipyramid are occupied by two pyrrolic nitrogen donors and a sigma-methyl ligand. The coordination sphere is completed by apical coordination of the alkoxy oxygen atom derived from alkanal or alkonone. The incorporation of aldehydes and ketones is stereoselective. Acidic desililation of alkanal compounds yields two aromatic N-confused porphyrin derivatives, that is, 3-(1-hydroxyalkyl)-5,10,15,20-tetraaryl-2-aza-21-carbaporphyrin and its oxidation product 3-alkanoyl-5,10,15,20-tetraaryl-2-aza-21-carbaporphyrin. The acid triggered desililation of ketone derivatives produces the equimolar amounts of N-confused porphyrin and ketone. The first spectroscopically identified step involves the protonation of the C(7) position affording the non-aromatic silicon(IV) complex. The density functional theory (DFT) has been applied to model the molecular and electronic structure of all species identified in the course of silicon insertion into the N-confused and N-fused porphyrin.

17. Addressing the Confusion Related to DNS, DNSc, and DSN Degrees, With Lessons for the Nursing Profession.

PubMed

Reid Ponte, Patricia; Nicholas, Patrice K

2015-07-01

18. Defusing Diffusion

ERIC Educational Resources Information Center

Dou, Remy; Hogan, DaNel; Kossover, Mark; Spuck, Timothy; Young, Sarah

2013-01-01

Diffusion has often been taught in science courses as one of the primary ways by which molecules travel, particularly within organisms. For years, classroom teachers have used the same common demonstrations to illustrate this concept (e.g., placing drops of food coloring in a beaker of water). Most of the time, the main contributor to the motion…

19. Demonstrating Diffusion

ERIC Educational Resources Information Center

Foy, Barry G.

1977-01-01

Two demonstrations are described. Materials and instructions for demonstrating movement of molecules into cytoplasm using agar blocks, phenolphthalein, and sodium hydroxide are given. A simple method for demonstrating that the rate of diffusion of a gas is inversely proportional to its molecular weight is also presented. (AJ)

20. Defusing Diffusion

ERIC Educational Resources Information Center

Dou, Remy; Hogan, DaNel; Kossover, Mark; Spuck, Timothy; Young, Sarah

2013-01-01

Diffusion has often been taught in science courses as one of the primary ways by which molecules travel, particularly within organisms. For years, classroom teachers have used the same common demonstrations to illustrate this concept (e.g., placing drops of food coloring in a beaker of water). Most of the time, the main contributor to the motion…

1. Demonstrating Diffusion

ERIC Educational Resources Information Center

Foy, Barry G.

1977-01-01

Two demonstrations are described. Materials and instructions for demonstrating movement of molecules into cytoplasm using agar blocks, phenolphthalein, and sodium hydroxide are given. A simple method for demonstrating that the rate of diffusion of a gas is inversely proportional to its molecular weight is also presented. (AJ)

2. Caffeine Confusion

MedlinePlus

... natural chemical found in tea leaves, coffee beans, cacao (the stuff used to make chocolate), and cola nuts (the plant that gives cola ... drinks, such as coffee, tea, hot cocoa, soda, chocolate, and some medicines . When humans drink or eat ...

3. Caffeine Confusion

MedlinePlus

... natural chemical found in tea leaves, coffee beans, cacao (the stuff used to make chocolate), and cola nuts (the plant that gives cola ... drinks, such as coffee, tea, hot cocoa, soda, chocolate, and some medicines . When humans drink or eat ...

4. NET Confusion

PubMed Central

Malachowa, Natalia; Kobayashi, Scott D.; Quinn, Mark T.; DeLeo, Frank R.

2016-01-01

Neutrophils are arguably the most important white blood cell for defense against bacterial and fungal infections. These leukocytes are produced in high numbers on a daily basis in humans and are recruited rapidly to injured/infected tissues. Phagocytosis and subsequent intraphagosomal killing and digestion of microbes have historically been the accepted means by which neutrophils carry out their role in innate host defense. Indeed, neutrophils contain and produce numerous cytotoxic molecules, including antimicrobial peptides, proteases, and reactive oxygen species, that are highly effective at killing the vast majority of ingested microbes. On the other hand, it is these characteristics – high numbers and toxicity – that endow neutrophils with the potential to injure and destroy host tissues. This potential is borne out by many inflammatory processes and diseases. Therefore, it is not surprising that host mechanisms exist to control virtually all steps in the neutrophil activation process and to prevent unintended neutrophil activation and/or lysis during the resolution of inflammatory responses or during steady-state turnover. The notion that neutrophil extracellular traps (NETs) form by cytolysis as a standard host defense mechanism seems inconsistent with these aforementioned neutrophil “containment” processes. It is with this caveat in mind that we provide perspective on the role of NETs in human host defense and disease. PMID:27446089

5. Cold confusion

SciTech Connect

Chapline, G.

1989-07-01

On March 23 two chemists, Martin Fleischmann and Stanley Pons startled the world with a press conference at the University of Utah where they announced that they had achieved nuclear fusion at room temperatures. As evidence they cited the production of ''excess'' amounts of heat in an electrochemical apparatus and observation of neutron production. While the production of heat in a chemical apparatus is not in itself unusual the observation of neutrons is certainly extraordinary. As it turned out, though, careful measurements of the neutron production in electrochemical apparatus similar to that used by Fleischmann and Pons carried out at dozens of other laboratories has shown that the neutron production fails by many orders of magnitude to support the assertion by Fleischmann and Pons that their discovery represents a new and cheap source of fusion power. In particular, independent measurements of the neutron production rate suggest that the actual rate of fusion energy production probably does not exceed 1 trillionth of a watt. This paper discusses the feasibility that cold fusion is actually being achieved. 7 refs.

6. Cold Confusion.

ERIC Educational Resources Information Center

Fogle, Pamela W.

1991-01-01

Public relations issues arising from the University of Utah's controversial announcement of research claiming achievement of nuclear fusion at room temperature are discussed. They include problems occurring before and after the initial press conference, secrecy vs. openness, research ethics, and effects lasting past the original incident and…

7. Cold Confusion.

ERIC Educational Resources Information Center

Fogle, Pamela W.

1991-01-01

Public relations issues arising from the University of Utah's controversial announcement of research claiming achievement of nuclear fusion at room temperature are discussed. They include problems occurring before and after the initial press conference, secrecy vs. openness, research ethics, and effects lasting past the original incident and…

8. Selective cerebral perfusion for cerebral protection: what we do know

PubMed Central

Tang, Gilbert H. L.

2013-01-01

Selective antegrade cerebral perfusion (SACP) for aortic arch surgery has evolved considerably since it was first reported. Various pressure rates have been investigated through animal models, as has the effect of warmer perfusate temperatures and hematocrit. Clinical research into pH management, the role of unilateral and bilateral perfusion, and core temperatures have further refined the procedure. We recommend the following protocol for SACP: perfusion pressure between 40-60 mmHg, flow rates between 6-10 mL/kg/min, and perfusate temperature of 20-28 °C; core cooling to 18-30 °C contingent on duration of arrest; alpha-stat pH management; hematocrit between 25-30%; near infrared spectroscopy to monitor cerebral perfusion; and bilateral perfusion when prolonged durations of SACP is anticipated. PMID:23977601

9. Pulmonary ventilation and perfusion abnormalities and ventilation perfusion imbalance in children with pulmonary atresia or extreme tetralogy of Fallot

SciTech Connect

Dowdle, S.C.; Human, D.G.; Mann, M.D. )

1990-08-01

Xenon-133 lung ventilation and perfusion scans were done preoperatively after cardiac catheterization and cineangiocardiography in 19 children; 6 had pulmonary atresia with an intact ventricular septum and hypoplastic right ventricle, 4 pulmonary atresia with associated complex univentricular heart, and 9 extreme Tetralogy of Fallot. The four patients with discrepancies in the sizes of the left and right pulmonary arteries on angiography had marked asymmetry of pulmonary perfusion and ventilation-perfusion imbalance on scintigraphy. Similar degrees of asymmetry and imbalance were present in 6 of the 15 children with equal-size pulmonary vessels. Asymmetry of pulmonary perfusion and ventilation-perfusion imbalance were associated with a poor prognosis.

10. The Groningen hypothermic liver perfusion pump: functional evaluation of a new machine perfusion system.

PubMed

van der Plaats, A; Maathuis, M H J; 'T Hart, N A; Bellekom, A A; Hofker, H S; van der Houwen, E B; Verkerke, G J; Leuvenink, H G D; Verdonck, P; Ploeg, R J; Rakhorst, G

2006-12-01

To improve preservation of donor livers, we have developed a portable hypothermic machine perfusion (HMP) system as an alternative for static cold storage. A prototype of the system was built and evaluated on functionality. Evaluation criteria included 24 h of adequate pressure controlled perfusion, sufficient oxygenation, a maintained 0-4 degrees C temperature and sterile conditions. Porcine livers were perfused with pump pressures that were set at 4 mmHg (continuous, portal vein) and 30/20 mmHg, at 60 BPM (pulsatile, hepatic artery). Control livers were preserved using the clinical golden standard: static cold storage. In the HMP group, pressure, flow and temperature were continuously monitored for 24 h. At time-points t = 0, 2, 4, 8, 12, and 24 h samples of University of Wisconsin machine preservation solution were taken for measurement of partial oxygen pressure (pO(2)) and lacto-dehydrogenase. Biopsies in every lobe were taken for histology and electron microscopy; samples of ice, preservation solution, liver surface, and bile were taken and cultured to determine sterility. Results showed that temperature was maintained at 0-4 degrees C; perfusion pressure was maintained at 4 mmHg and 30/20 mmHg for portal vein and hepatic artery, respectively. Flow was approximately 350 and 80 ml/min, respectively, but decreased in the portal vein, probably due to edema formation. Arterial pO(2) was kept at 100 kPa. Histology showed complete perfusion of the liver with no major damage to hepatocytes, bile ducts, and non-parenchymal cells compared to control livers. The machine perfusion system complied to the design criteria and will have to demonstrate the superiority of machine perfusion over cold storage in transplant experiments.

11. 29 CFR 18.403 - Exclusion of relevant evidence on grounds of confusion or waste of time.

Code of Federal Regulations, 2010 CFR

2010-07-01

... PROCEDURE FOR ADMINISTRATIVE HEARINGS BEFORE THE OFFICE OF ADMINISTRATIVE LAW JUDGES Rules of Evidence Relevancy and Its Limits § 18.403 Exclusion of relevant evidence on grounds of confusion or waste of time... 29 Labor 1 2010-07-01 2010-07-01 true Exclusion of relevant evidence on grounds of confusion or...

12. Diffusion bonding

DOEpatents

Anderson, Robert C.

1976-06-22

1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

13. Effect of cardiac dysrhythmia on cerebral perfusion.

PubMed

Sand, B J; Rose, H B; Barker, W F

1976-07-01

Extracranial carotid arterial obstructive disease has been the entity most commonly associated with transient cerebrovascular insufficiency. A nonobstructive, frequently overlooked cause of cerebral ischemia is cardiac dysrhythmia. We have explored this by observations of experimental animals and of man. Blood flow and pressure in the carotid arteries of dogs were shown to be decreased by mechnically induced premature ventricular contractions. The significance of the cardiogenic contribution to altered cerebrovascular perfusion was studied by ocular and brachial plethysmography in 210 patients suspected by history of having carotid arterial insufficiency. Of the 210 patients, 62 demonstrated abnormal ocular plethysmographic recordings, and of those, nine had dysrhythmias associated with significant deficits of ocular perfusion. Five patients whose recordings were technically suitable for publication are presented to demonstrate the bizarre ocular plethysmographic recordings seen during the dysrhythmic cycle.

14. Imaging of drug effects in perfused liver

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.

15. Assessment of differential pulmonary blood flow using perfusion magnetic resonance imaging: comparison with radionuclide perfusion scintigraphy.

PubMed

Molinari, Francesco; Fink, Christian; Risse, Frank; Tuengerthal, Siegfried; Bonomo, Lorenzo; Kauczor, Hans-Ulrich

2006-08-01

We sought to assess the agreement between lung perfusion ratios calculated from pulmonary perfusion magnetic resonance imaging (MRI) and those calculated from radionuclide (RN) perfusion scintigraphy. A retrospective analysis of MR and RN perfusion scans was conducted in 23 patients (mean age, 60 +/- 14 years) with different lung diseases (lung cancer = 15, chronic obstructive pulmonary disease = 4, cystic fibrosis = 2, and mesothelioma = 2). Pulmonary perfusion was assessed by a time-resolved contrast-enhanced 3D gradient-echo pulse sequence using parallel imaging and view sharing (TR = 1.9 milliseconds; TE = 0.8 milliseconds; parallel imaging acceleration factor = 2; partition thickness = 4 mm; matrix = 256 x 96; in-plane spatial resolution = 1.87 x 3.75 mm; scan time for each 3D dataset = 1.5 seconds), using gadolinium-based contrast agents (injection flow rate = 5 mL/s, dose = 0.1 mmol/kg of body weight). The peak concentration (PC) of the contrast agent bolus, the pulmonary blood flow (PBF), and blood volume (PBV) were computed from the signal-time curves of the lung. Left-to-right ratios of pulmonary perfusion were calculated from the MR parameters and RN counts. The agreement between these ratios was assessed for side prevalence (sign test) and quantitatively (Deming-regression). MR and RN ratios agreed on side prevalence in 21 patients (91%) with PC, in 20 (87%) with PBF, and in 17 (74%) with PBV. The MR estimations of left-to-right perfusion ratios correlated significantly with those of RN perfusion scans (P < 0.01). The correlation was higher using PC (r = 0.67) and PBF (r = 0.66) than using PBV (r = 0.50). The MR ratios computed from PBF showed the highest accuracy, followed by those from PC and PBV. Independently from the MR parameter used, in some patients the quantitative difference between the MR and RN ratios was not negligible. Pulmonary perfusion MRI can be used to assess the differential blood flow of the lung. Further studies in a larger group

16. The effect of music listening on acute confusion and delirium in elders undergoing elective hip and knee surgery.

PubMed

McCaffrey, Ruth; Locsin, Rozzano

2004-09-01

This study was undertaken to determine the effect of music on elders undergoing elective hip and knee surgery who experience acute confusion and delirium postoperatively. Postoperative confusion and delirium in elders often cause complications that negatively effect recovery. Music listening was introduced as an intervention to an experimental group. Nurses documented episodes of acute confusion and delirium experienced by elders postsurgically. Scores from a readiness-to-ambulate profile to determine if patients were cognitively ready for postoperative therapy were evaluated. There was a significant decrease in the number of episodes of postoperative confusion among those in the experimental group compared with those in the non-listening control group. In addition, the experimental group had significantly higher scores on the readiness-to-ambulate profile than the control group. These findings indicate that music listening is an effective nursing intervention that can be used to decrease acute postoperative confusion and delirium in elders undergoing elective hip and knee surgery.

17. Individual differences in degree of handedness and somesthetic asymmetry predict individual differences in left-right confusion.

PubMed

Vingerhoets, Guy; Sarrechia, Iemke

2009-12-01

Confusion or frustration connected with daily demands involving left-right discrimination is a common observation even in neurologically intact adults. We aimed to test the hypothesis that the degree of left-right confusion is associated with bodily asymmetry. Sixty-two female volunteers performed a left-right decision task that required fast responses to visually presented directional words (left, right, up, down) or pictograms (<--, -->, upward arrow, downward arrow). Participants also performed several tests that measured asymmetry of handedness, grip strength, and tactile sensitivity, and completed self-reports on left-right confusion and perceived bodily asymmetry. Results showed significant correlations between left-right confusion and the degree of handedness and asymmetry in tactile sensitivity. These results suggest that individuals who reveal a stronger internal bias between both sides of the body show less left-right confusion than people with less salient bodily asymmetry.

18. Maximal perfusion of skeletal muscle in man.

PubMed Central

Andersen, P; Saltin, B

1985-01-01

Five subjects exercised with the knee extensor of one limb at work loads ranging from 10 to 60 W. Measurements of pulmonary oxygen uptake, heart rate, leg blood flow, blood pressure and femoral arterial-venous differences for oxygen and lactate were made between 5 and 10 min of the exercise. Flow in the femoral vein was measured using constant infusion of saline near 0 degrees C. Since a cuff was inflated just below the knee during the measurements and because the hamstrings were inactive, the measured flow represented primarily the perfusion of the knee extensors. Blood flow increased linearly with work load right up to an average value of 5.7 l min-1. Mean arterial pressure was unchanged up to a work load of 30 W, but increased thereafter from 100 to 130 mmHg. The femoral arterial-venous oxygen difference at maximum work averaged 14.6% (v/v), resulting in an oxygen uptake of 0.80 l min-1. With a mean estimated weight of the knee extensors of 2.30 kg the perfusion of maximally exercising skeletal muscle of man is thus in the order of 2.5 l kg-1 min-1, and the oxygen uptake 0.35 l kg-1 min-1. Limitations in the methods used previously to determine flow and/or the characteristics of the exercise model used may explain why earlier studies in man have failed to demonstrate the high perfusion of muscle reported here. It is concluded that muscle blood flow is closely related to the oxygen demand of the exercising muscles. The hyperaemia at low work intensities is due to vasodilatation, and an elevated mean arterial blood pressure only contributes to the linear increase in flow at high work rates. The magnitude of perfusion observed during intense exercise indicates that the vascular bed of skeletal muscle is not a limiting factor for oxygen transport. PMID:4057091

19. Myocardial perfusion and left ventricular function indices assessed by gated myocardial perfusion SPECT in methamphetamine abusers.

PubMed

Dadpour, Bita; Dabbagh Kakhki, Vahid R; Afshari, Reza; Dorri-Giv, Masoumeh; Mohajeri, Seyed A R; Ghahremani, Somayeh

2016-12-01

Methamphetamine (MA) is associated with alterations of cardiac structure and function, although it is less known. In this study, we assessed possible abnormality in myocardial perfusion and left ventricular function using gated myocardial perfusion SPECT. Fifteen patients with MA abuse, on the basis of Diagnostic and Statistical Manual of Mental Disorders, 4th ed. (DSM-IV) MA dependency determined by Structured Clinical Interview for DSM-IV, underwent 2-day dipyridamole stress/rest Tc-sestamibi gated myocardial perfusion SPECT. An average daily dose of MA use was 0.91±1.1 (0.2-4) g. The duration of MA use was 3.4±2.1 (1-7) years. In visual and semiquantitative analyses, all patients had normal gated myocardial perfusion SPECT, with no perfusion defects. In all gated SPECT images, there was no abnormality in left ventricular wall motion and thickening. All summed stress scores and summed rest scores were below 3. Calculated left ventricular functional indices including the end-diastolic volume, end-systolic volume, and left ventricular ejection fraction were normal. Many cardiac findings because of MA mentioned in previous reports are less likely because of significant epicardial coronary artery stenosis.

20. 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.

1. Perfusion patterns in migraine with aura.

PubMed

Förster, Alex; Wenz, Holger; Kerl, Hans U; Brockmann, Marc A; Groden, Christoph

2014-10-01

Migraine with aura is a common neurological disorder, and differentiation from transient ischemic attack or stroke based on clinical symptoms may be difficult. From an MRI report database we identified 33 patients with migraine with aura and compared these to 33 age-matched ischemic stroke patients regarding perfusion patterns on perfusion-weighted imaging (PWI)-derived maps: time to peak (TTP), mean transit time (MTT), and cerebral blood flow and volume (CBF, CBV). In 18/33 (54.5%) patients with migraine with aura, TTP showed areas of hypoperfusion, most of these not limited to the territory of a specific artery but affecting two or more vascular territories. In patients with migraine with aura, TTP (1.09 ± 0.05 vs. 1.47 ± 0.40, p < 0.001) and MTT ratios (1.01 ± 0.10 vs. 1.19 ± 0.21, p = 0.003) were significantly lower compared to patients with ischemic stroke. In contrast to this, CBF and CBV ratios did not differ significantly between both groups. Migraine aura is usually associated with a perfusion deficit not limited to a specific vascular territory, and only a moderate increase of TTP. Thus, hypoperfusion restricted to a single vascular territory in combination with a marked increase of TTP or MTT may be regarded as atypical for migraine aura and suggestive of acute ischemic stroke. © International Headache Society 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

2. Vascular perfusion in horses with chronic laminitis.

PubMed

Hood, D M; Grosenbaugh, D A; Slater, M R

1994-05-01

Vascular perfusion casts were used to define and characterise the macroscopic perfusion defects present in the distal digit of 11 horses affected by chronic laminitis. Five clinically normal horses were used as controls. Based on clinical history and clinical status, horses with chronic laminitis were classified as being potentially treatable or clinically refractory. Eleven macroscopic vascular defects were noted in the casts from horses with laminitis. Four types of lesions were identified in the submural laminar circulation, 3 in the coronary bed and 4 were associated with the solar circulation. Multiple defects were present and a definite trend was noted for the perfusion defects to be worse in the casts of clinically refractory subjects than in those considered treatable. This information suggests that evaluation of circulatory status should add significantly to the ability to separate treatable from clinically refractory patients. Results also indicated that ventral displacement of the third phalanx (sinkers) and compression of the solar vasculature are more prevalent than is presently thought.

3. Noncontact blood perfusion mapping in clinical applications

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.

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. CT perfusion: principles, applications, and problems

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.

6. Dynamic CT perfusion measurement in a cardiac phantom.

PubMed

Ziemer, Benjamin P; Hubbard, Logan; Lipinski, Jerry; Molloi, Sabee

2015-10-01

Widespread clinical implementation of dynamic CT myocardial perfusion has been hampered by its limited accuracy and high radiation dose. The purpose of this study was to evaluate the accuracy and radiation dose reduction of a dynamic CT myocardial perfusion technique based on first pass analysis (FPA). To test the FPA technique, a pulsatile pump was used to generate known perfusion rates in a range of 0.96-2.49 mL/min/g. All the known perfusion rates were determined using an ultrasonic flow probe and the known mass of the perfusion volume. FPA and maximum slope model (MSM) perfusion rates were measured using volume scans acquired from a 320-slice CT scanner, and then compared to the known perfusion rates. The measured perfusion using FPA (P(FPA)), with two volume scans, and the maximum slope model (P(MSM)) were related to known perfusion (P(K)) by P(FPA) = 0.91P(K) + 0.06 (r = 0.98) and P(MSM) = 0.25P(K) - 0.02 (r = 0.96), respectively. The standard error of estimate for the FPA technique, using two volume scans, and the MSM was 0.14 and 0.30 mL/min/g, respectively. The estimated radiation dose required for the FPA technique with two volume scans and the MSM was 2.6 and 11.7-17.5 mSv, respectively. Therefore, the FPA technique can yield accurate perfusion measurements using as few as two volume scans, corresponding to approximately a factor of four reductions in radiation dose as compared with the currently available MSM. In conclusion, the results of the study indicate that the FPA technique can make accurate dynamic CT perfusion measurements over a range of clinically relevant perfusion rates, while substantially reducing radiation dose, as compared to currently available dynamic CT perfusion techniques.

7. Getting the Picture: Iconicity Does Not Affect Representation-Referent Confusion

PubMed Central

Wimmer, Marina C.; Robinson, Elizabeth J.; Koenig, Laura; Corder, Emma

2014-01-01

Three experiments examined 3- to 5-year-olds' (N = 428) understanding of the relationship between pictorial iconicity (photograph, colored drawing, schematic drawing) and the real world referent. Experiments 1 and 2 explored pictorial iconicity in picture-referent confusion after the picture-object relationship has been established. Pictorial iconicity had no effect on referential confusion when the referent changed after the picture had been taken/drawn (Experiment 1) and when the referent and the picture were different from the outset (Experiment 2). Experiment 3 investigated whether children are sensitive to iconicity to begin with. Children deemed photographs from a choice of varying iconicity representations as best representations for object reference. Together, findings suggest that iconicity plays a role in establishing a picture-object relation per se but is irrelevant once children have accepted that a picture represents an object. The latter finding may reflect domain general representational abilities. PMID:25247708

8. Concept confusion and concept discernment in basic magnetism using analogical reasoning

Lemmer, Miriam; Nicodimus Morabe, Olebogeng

2017-07-01

Analogical reasoning is central to all learning, whether in daily life situations, in the classroom or while doing research. Although analogies can aid the learning process of making sense of phenomena and understanding new ideas in terms of known ideas, these should be used with care. This article reports a study of the use of analogies and the consequences of this use in the teaching of magnetism with special reference to misconceptions. We begin by identifying concept confusion and associated misconceptions in magnetism due to in-service physics teachers’ spontaneous analogical reasoning. Two analogy-based experiments that can be used to convert such concept confusion to discernment are then described. These experiments focus on understanding basic principles about sources and interactions of magnetic fields and implement the constructivist learning processes of discrimination and generalization. Lastly, recommendations towards reinforcement of conceptual understanding of basic magnetism in its relation to electricity are proposed.

9. Autonomous technology - sources of confusion: a model for explanation and prediction of conceptual shifts.

PubMed

Stensson, Patrik; Jansson, Anders

2014-01-01

Today, autonomous is often used for technology with a more intelligent self-management capability than common automation. This concept usage is maladaptive, ignoring both the distinction between autonomy and heteronomy according to Kant's categorical imperative and that the meaning of autonomy implies qualities technology cannot have. Being autonomous is about having the right to be wrong, a right justified by accountability and insightful understanding of real-life values, and it is about being externally uncontrollable. The contemporary use of autonomy as well as similar concepts is discussed and a model is presented showing how six sources of confusion interact in a vicious circle that impede human authority and autonomy. Our goal is to sort out these confusions and contribute to a development in which the different roles of machines and people, and human responsibilities, are explicated rather than blurred, which should facilitate the forming of truly beneficial and complementary systems.

10. Right-left confusion in Gerstmann's syndrome: a model of body centered spatial orientation.

PubMed

Gold, M; Adair, J C; Jacobs, D H; Heilman, K M

1995-06-01

Gerstmann's syndrome encompasses the tetrad of finger agnosia, agraphia, acalculia and right-left confusion and is associated with lesions of the dominant angular gyrus. The localizing value of this syndrome has been questioned because multiple mechanisms can account for each of the components of the syndrome. We present the case of a man who developed Gerstmann's syndrome following a focal infarct of the left angular gyrus. The patient's right-left confusion could not be accounted for by either an aphasia or a degraded body schema. A series of experiments that investigated the patient's spatial mapping system by progressively restricting the degrees of freedom for spatial rotation revealed an isolated defect in deriving the relative position of an object along the horizontal axis. Defective horizontal mapping can account for the other components of Gerstmann's syndrome because they all share a common dependency on relative horizontal positioning.

11. Ontological confusions but not mentalizing abilities predict religious belief, paranormal belief, and belief in supernatural purpose.

PubMed

Lindeman, Marjaana; Svedholm-Häkkinen, Annika M; Lipsanen, Jari

2015-01-01

The current research tested the hypothesis that the abilities for understanding other people's minds give rise to the cognitive biases that underlie supernatural beliefs. We used structural equation modeling (N=2789) to determine the roles of various mentalizing tendencies, namely self-reported affective and cognitive empathy (i.e., mind reading), actual cognitive and affective empathic abilities, hyper-empathizing, and two cognitive biases (core ontological confusions and promiscuous teleology) in giving rise to supernatural beliefs. Support for a path from mentalizing abilities through cognitive biases to supernatural beliefs was weak. The relationships of mentalizing abilities with supernatural beliefs were also weak, and these relationships were not substantially mediated by cognitive biases. Core ontological confusions emerged as the best predictor, while promiscuous teleology predicted only a small proportion of variance. The results were similar for religious beliefs, paranormal beliefs, and for belief in supernatural purpose. Copyright © 2014 Elsevier B.V. All rights reserved.

12. A pain in the fetus: toward ending confusion about fetal pain.

PubMed

Benatar, D; Benatar, M

2001-02-01

Are fetuses, at any stage of their development, capable of feeling pain? In his paper, "Locating the Beginnings of Pain," Stuart Derbyshire argues that they are not. We argue that he reaches this conclusion by way of conceptual confusion, a misreading of the available scientific data and the inclusion of irrelevant data. Despite his assertion to the contrary, the work of most scientists in the area supports the conclusion that fetuses can feel pain. At the outset we examine the concept of pain and distinguish it from the allied concept of nociception, with which it is sometimes confused. With the relevant conceptual framework in place, we elucidate the problem of determining when, in its development, a human becomes capable of feeling pain. We then examine the available data showing how, on balance, it tends more to support than undermine the claim that fetuses of around 28 to 30 weeks' gestation are capable of feeling pain.

13. Prostate Diffusion Imaging with Distortion Correction

PubMed Central

Rakow-Penner, Rebecca A.; White, Nathan S.; Margolis, Daniel J. A.; Parsons, J. Kellogg; Schenker-Ahmed, Natalie; Kuperman, Joshua M.; Bartsch, Hauke; Choi, Hyung W.; Bradley, William G.; Shabaik, Ahmed; Huang, Jiaoti; Liss, Michael A.; Marks, Leonard; Kane, Christopher J.; Reiter, Robert E.; Raman, Steven S.; Karow, David S.; Dale, Anders M.

2015-01-01

Purpose Diffusion imaging in the prostate is susceptible to distortion from B0 inhomogeneity. Distortion correction in prostate imaging is not routinely performed, resulting in diffusion images without accurate localization of tumors. We performed and evaluated distortion correction for diffusion imaging in the prostate. Materials and Methods 28 patients underwent pre-operative MRI (T2, Gadolinium perfusion, diffusion at b = 800 s/mm2). The restriction spectrum protocol parameters included b-values of 0, 800, 1500, and 4000 s/mm2 in 30 directions for each nonzero b-value. To correct for distortion, forward and reverse trajectories were collected at b = 0 s/mm2. Distortion maps were generated to reflect the offset of the collected data versus the corrected data. Whole-mount histology, was available for correlation. Results: Across the 27 patients evaluated (excluding one patient due to data collection error), the average root mean square distortion distance of the prostate was 3.1 mm (standard deviation, 2.2 mm; and maximum distortion, 12 mm). Conclusion Improved localization of prostate cancer by MRI will allow better surgical planning, targeted biopsies and image-guided treatment therapies. Distortion distances of up to 12 mm due to standard diffusion imaging may grossly misdirect treatment decisions. Distortion correction for diffusion imaging in the prostate improves tumor localization. PMID:26220859

14. 3D Printed Vascular Networks Enhance Viability in High-Volume Perfusion Bioreactor.

PubMed

Ball, Owen; Nguyen, Bao-Ngoc B; Placone, Jesse K; Fisher, John P

2016-12-01

There is a significant clinical need for engineered bone graft substitutes that can quickly, effectively, and safely repair large segmental bone defects. One emerging field of interest involves the growth of engineered bone tissue in vitro within bioreactors, the most promising of which are perfusion bioreactors. Using bioreactor systems, tissue engineered bone constructs can be fabricated in vitro. However, these engineered constructs lack inherent vasculature and once implanted, quickly develop a necrotic core, where no nutrient exchange occurs. Here, we utilized COMSOL modeling to predict oxygen diffusion gradients throughout aggregated alginate constructs, which allowed for the computer-aided design of printable vascular networks, compatible with any large tissue engineered construct cultured in a perfusion bioreactor. We investigated the effect of 3D printed macroscale vascular networks with various porosities on the viability of human mesenchymal stem cells in vitro, using both gas-permeable, and non-gas permeable bioreactor growth chamber walls. Through the use of 3D printed vascular structures in conjunction with a tubular perfusion system bioreactor, cell viability was found to increase by as much as 50% in the core of these constructs, with in silico modeling predicting construct viability at steady state.

15. A Device for Long-Term Perfusion, Imaging, and Electrical Interfacing of Brain Tissue In vitro.

PubMed

Killian, Nathaniel J; Vernekar, Varadraj N; Potter, Steve M; Vukasinovic, Jelena

2016-01-01

Distributed microelectrode array (MEA) recordings from consistent, viable, ≥500 μm thick tissue preparations over time periods from days to weeks may aid in studying a wide range of problems in neurobiology that require in vivo-like organotypic morphology. Existing tools for electrically interfacing with organotypic slices do not address necrosis that inevitably occurs within thick slices with limited diffusion of nutrients and gas, and limited removal of waste. We developed an integrated device that enables long-term maintenance of thick, functionally active, brain tissue models using interstitial perfusion and distributed recordings from thick sections of explanted tissue on a perforated multi-electrode array. This novel device allows for automated culturing, in situ imaging, and extracellular multi-electrode interfacing with brain slices, 3-D cell cultures, and potentially other tissue culture models. The device is economical, easy to assemble, and integrable with standard electrophysiology tools. We found that convective perfusion through the culture thickness provided a functional benefit to the preparations as firing rates were generally higher in perfused cultures compared to their respective unperfused controls. This work is a step toward the development of integrated tools for days-long experiments with more consistent, healthier, thicker, and functionally more active tissue cultures with built-in distributed electrophysiological recording and stimulation functionality. The results may be useful for the study of normal processes, pathological conditions, and drug screening strategies currently hindered by the limitations of acute (a few hours long) brain slice preparations.

16. A Device for Long-Term Perfusion, Imaging, and Electrical Interfacing of Brain Tissue In vitro

PubMed Central

Killian, Nathaniel J.; Vernekar, Varadraj N.; Potter, Steve M.; Vukasinovic, Jelena

2016-01-01

Distributed microelectrode array (MEA) recordings from consistent, viable, ≥500 μm thick tissue preparations over time periods from days to weeks may aid in studying a wide range of problems in neurobiology that require in vivo-like organotypic morphology. Existing tools for electrically interfacing with organotypic slices do not address necrosis that inevitably occurs within thick slices with limited diffusion of nutrients and gas, and limited removal of waste. We developed an integrated device that enables long-term maintenance of thick, functionally active, brain tissue models using interstitial perfusion and distributed recordings from thick sections of explanted tissue on a perforated multi-electrode array. This novel device allows for automated culturing, in situ imaging, and extracellular multi-electrode interfacing with brain slices, 3-D cell cultures, and potentially other tissue culture models. The device is economical, easy to assemble, and integrable with standard electrophysiology tools. We found that convective perfusion through the culture thickness provided a functional benefit to the preparations as firing rates were generally higher in perfused cultures compared to their respective unperfused controls. This work is a step toward the development of integrated tools for days-long experiments with more consistent, healthier, thicker, and functionally more active tissue cultures with built-in distributed electrophysiological recording and stimulation functionality. The results may be useful for the study of normal processes, pathological conditions, and drug screening strategies currently hindered by the limitations of acute (a few hours long) brain slice preparations. PMID:27065793

17. DISENTANGLING CONFUSED STARS AT THE GALACTIC CENTER WITH LONG-BASELINE INFRARED INTERFEROMETRY

SciTech Connect

Stone, Jordan M.; Eisner, J. A.; Monnier, J. D.; Woillez, J.; Wizinowich, P.; Pott, J.-U.; Ghez, A. M. E-mail: jeisner@email.arizona.edu

2012-08-01

We present simulations of Keck Interferometer ASTRA and VLTI GRAVITY observations of mock star fields in orbit within {approx}50 mas of Sgr A*. Dual-field phase referencing techniques, as implemented on ASTRA and planned for GRAVITY, will provide the sensitivity to observe Sgr A* with long-baseline infrared interferometers. Our results show an improvement in the confusion noise limit over current astrometric surveys, opening a window to study stellar sources in the region. Since the Keck Interferometer has only a single baseline, the improvement in the confusion limit depends on source position angles. The GRAVITY instrument will yield a more compact and symmetric point-spread function, providing an improvement in confusion noise which will not depend as strongly on position angle. Our Keck results show the ability to characterize the star field as containing zero, few, or many bright stellar sources. We are also able to detect and track a source down to m{sub K} {approx} 18 through the least confused regions of our field of view at a precision of {approx}200 {mu}as along the baseline direction. This level of precision improves with source brightness. Our GRAVITY results show the potential to detect and track multiple sources in the field. GRAVITY will perform {approx}10 {mu}as astrometry on an m{sub K} = 16.3 source and {approx}200 {mu}as astrometry on an m{sub K} = 18.8 source in 6 hr of monitoring a crowded field. Monitoring the orbits of several stars will provide the ability to distinguish between multiple post-Newtonian orbital effects, including those due to an extended mass distribution around Sgr A* and to low-order general relativistic effects. ASTRA and GRAVITY both have the potential to detect and monitor sources very close to Sgr A*. Early characterizations of the field by ASTRA, including the possibility of a precise source detection, could provide valuable information for future GRAVITY implementation and observation.

PubMed Central

Bernard, Alfred

2015-01-01

Background Cadmium (Cd) risk assessment presently relies on tubular proteinuria as a critical effect and urinary Cd (U-Cd) as an index of the Cd body burden. Based on this paradigm, regulatory bodies have reached contradictory conclusions regarding the safety of Cd in food. Adding to the confusion, epidemiological studies implicate environmental Cd as a risk factor for bone, cardiovascular, and other degenerative diseases at exposure levels that are much lower than points of departure used for setting food standards. Objective The objective was to examine whether the present confusion over Cd risks is not related to conceptual or methodological problems. Discussion The cornerstone of Cd risk assessment is the assumption that U-Cd reflects the lifetime accumulation of the metal in the body. The validity of this assumption as applied to the general population has been questioned by recent studies revealing that low-level U-Cd varies widely within and between individuals depending on urinary flow, urine collection protocol, and recent exposure. There is also evidence that low-level U-Cd increases with proteinuria and essential element deficiencies, two potential confounders that might explain the multiple associations of U-Cd with common degenerative diseases. In essence, the present Cd confusion might arise from the fact that this heavy metal follows the same transport pathways as plasma proteins for its urinary excretion and the same transport pathways as essential elements for its intestinal absorption. Conclusions The Cd risk assessment paradigm needs to be rethought taking into consideration that low-level U-Cd is strongly influenced by renal physiology, recent exposure, and factors linked to studied outcomes. Citation Bernard A. 2016. Confusion about cadmium risks: the unrecognized limitations of an extrapolated paradigm. Environ Health Perspect 124:1–5; http://dx.doi.org/10.1289/ehp.1509691 PMID:26058085

19. Specification of IRAS confused regions. Rept. for 11 Jan-11 May 90

SciTech Connect

Kennealy, J.P.; Woodward, C.E.; Korte, R.M.

1990-06-19

This document reports on the efforts to define the IRAS confused regions. The subset will be limited by the availability of survey data in the regions which are identified as point source confused by the current (Ver 2.0) IRAS point source catalog (PSC). Available coincident AO data will be an important validation source. The sensitivity and spatial resolution capabilities of the IRAS telescope failed to resolve individual sources in many regions of high source density. Approximately 10% of the sources catalogued in the PSC are tagged as 'confused' in some way; the location of a source, the number of sources at a location, the temporal occurrence and variation of a source, and/or the intensity of a source(s) was not discernible by the source identification/discrimination methods used to compile the PSC. In these regions of infrared clutter, the PSC can underestimate the number of point sources by as much as a factor of 3 to 5 in the IRAS Bands 1 and 2 (12 and 25 micrometers respectively). Analysis for improved source counts is designed to enhance the description and spatial definition of the mid- and long wavelength infrared celestial background, and includes generation of high spatial resolution images of the confused regions. Analysis of these images will improve the accuracy of source counts, locations, and flux estimates in the PSC. More detailed knowledge of the high source density regions will improve our ability to understand star formation and galactic evolution. It will also greatly improve our knowledge of a type of celestial background which presents a serious clutter problem for space-born surveillance system sensors.

20. Preparation to care for confused older patients in general hospitals: a study of UK health professionals

PubMed Central

Griffiths, Amanda; Knight, Alec; Harwood, Rowan; Gladman, John R.F.

2014-01-01

Background and Objective: in the UK, two-thirds of patients in general hospitals are older than 70, of whom half have dementia or delirium or both. Our objective was to explore doctors, nurses and allied health professionals' perceptions of their preparation to care for confused older patients on general hospital wards. Methods: using a quota sampling strategy across 11 medical, geriatric and orthopaedic wards in a British teaching hospital, we conducted 60 semi-structured interviews with doctors, nurses and allied healthcare professionals and analysed the data using the Consensual Qualitative Research approach. Results: there was consensus among participants that education, induction and in-service training left them inadequately prepared and under-confident to care for confused older patients. Many doctors reported initial assessments of confused older patients as difficult. They admitted inadequate knowledge of mental health disorders, including the diagnostic features of delirium and dementia. Handling agitation and aggression were considered top priorities for training, particularly for nurses. Multidisciplinary team meetings were highly valued but were reported as too infrequent. Participants valued specialist input but reported difficulties gaining such support. Communication with confused patients was regarded as particularly challenging, both in terms of patients making their needs known, and staff conveying information to patients. Participants reported emotional and behavioural responses including frustration, stress, empathy, avoidance and low job satisfaction. Conclusion: our findings indicate that a revision of training across healthcare professions in the UK is required, and that increased specialist support should be provided, so that the workforce is properly prepared to care for older patients with cognitive problems. PMID:24165310

1. MSTAR object classification and confuser and clutter rejection using Minace filters

Patnaik, Rohit; Casasent, David

2006-05-01

This paper presents the status of our SAR automatic target recognition (ATR) work on the Moving and Stationary Target Acquisition and Recognition (MSTAR) public database using the minimum noise and correlation energy (MINACE) distortion-invariant filter (DIF). We use a subset of the MSTAR public database for the benchmark three-class problem and we address confuser and clutter rejection. To handle the full 360° range of aspect view in MSTAR data, we use a set of Minace filters for each object; each filter should recognize the object (and its variants) in some angular range. We use fewer DIFs per object than prior work did. The Minace parameter c trades-off distortion-tolerance (recognition) versus discrimination (confuser/clutter rejection) performance. Our filter synthesis algorithm automatically selects the Minace filter parameter c and selects the training set images to be included in the filter, so that the filter can achieve both good recognition and good confuser and clutter rejection performance; this is achieved using a training and validation set. In our new filter synthesis method, no confuser, clutter, or test set data are used. The peak-to-correlation energy (PCE) ratio is used as the correlation plane metric in both filter synthesis and in tests, since it works better than correlation peak height. In tests, we do not assume that the test input's pose is known (as most prior work does), since pose estimation of SAR objects has a large margin of error; we describe our procedure for proper use of pose estimates in MSTAR recognition. The use of circular versus linear correlations is addressed. We also address the use of multi-look SAR data to improve performance.

2. 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

3. Noninvasive stress testing of myocardial perfusion defects: head-to-head comparison of thallium-201 SPECT to MRI perfusion.

PubMed

Vincenti, Gabriella; Nkoulou, René; Steiner, Charles; Imperiano, Hestia; Ambrosio, Giuseppe; Mach, François; Ratib, Osman; Vallee, Jean-Paul; Schindler, Thomas H

2009-01-01

To evaluate the diagnostic value of magnetic resonance imaging (MRI) of myocardial perfusion in the assessment of flow-limiting epicardial stenosis in a head-to-head comparison with abnormal thallium-201 ((201)TI) single photon emission tomography (SPECT) studies in patients with predominantly known coronary artery disease (CAD). Twenty-one patients (mean age 65 +/- 10 years) with reversible myocardial perfusion defects on (201)TI-SPECT images during dipyridamole-stimulated hyperemia were recruited for study purpose. Within 5 days of the (201)TI-SPECT study, myocardial perfusion was studied again with MRI during dipyridamole stimulation and at rest. Overall, (201)TI-SPECT identified 30 reversible regional perfusion defects. The sensitivity to detect hypoperfused segments was 70% (21/30) with the GRE-MRI perfusion analysis with (201)TI-SPECT as reference. When patients were subgrouped according to the extent of regional reversible perfusion defects on (201)TI-SPECT, mild- (SDS: 2-4), moderate- (SDS: 5-8), and severe- (SDS > 8) perfusion defects were also identified by GRE-MRI perfusion analysis in 75% (6/8), in 56% (9/16) and 100% (6/6), respectively. GRE-MRI first-pass stress perfusion imaging may not identify up to 30% of mild-to-moderate perfusion defects in a group of preselected patients with predominantly known CAD and abnormal (201)TI-SPECT studies.

4. Perfusion phantom: An efficient and reproducible method to simulate myocardial first-pass perfusion measurements with cardiovascular magnetic resonance.

PubMed

Chiribiri, Amedeo; Schuster, Andreas; Ishida, Masaki; Hautvast, Gilion; Zarinabad, Niloufar; Morton, Geraint; Otton, James; Plein, Sven; Breeuwer, Marcel; Batchelor, Philip; Schaeffter, Tobias; Nagel, Eike

2013-03-01

The aim of this article is to describe a novel hardware perfusion phantom that simulates myocardial first-pass perfusion allowing comparisons between different MR techniques and validation of the results against a true gold standard. MR perfusion images were acquired at different myocardial perfusion rates and variable doses of gadolinium and cardiac output. The system proved to be sensitive to controlled variations of myocardial perfusion rate, contrast agent dose, and cardiac output. It produced distinct signal intensity curves for perfusion rates ranging from 1 to 10 mL/mL/min. Quantification of myocardial blood flow by signal deconvolution techniques provided accurate measurements of perfusion. The phantom also proved to be very reproducible between different sessions and different operators. This novel hardware perfusion phantom system allows reliable, reproducible, and efficient simulation of myocardial first-pass MR perfusion. Direct comparison between the results of image-based quantification and reference values of flow and myocardial perfusion will allow development and validation of accurate quantification methods.

5. Visual crowding is a combination of an increase of positional uncertainty, source confusion, and featural averaging.

PubMed

Harrison, William J; Bex, Peter J

2017-04-05

Although we perceive a richly detailed visual world, our ability to identify individual objects is severely limited in clutter, particularly in peripheral vision. Models of such "crowding" have generally been driven by the phenomenological misidentifications of crowded targets: using stimuli that do not easily combine to form a unique symbol (e.g. letters or objects), observers typically confuse the source of objects and report either the target or a distractor, but when continuous features are used (e.g. orientated gratings or line positions) observers report a feature somewhere between the target and distractor. To reconcile these accounts, we develop a hybrid method of adjustment that allows detailed analysis of these multiple error categories. Observers reported the orientation of a target, under several distractor conditions, by adjusting an identical foveal target. We apply new modelling to quantify whether perceptual reports show evidence of positional uncertainty, source confusion, and featural averaging on a trial-by-trial basis. Our results show that observers make a large proportion of source-confusion errors. However, our study also reveals the distribution of perceptual reports that underlie performance in this crowding task more generally: aggregate errors cannot be neatly labelled because they are heterogeneous and their structure depends on target-distractor distance.

6. Visual crowding is a combination of an increase of positional uncertainty, source confusion, and featural averaging

PubMed Central

Harrison, William J.; Bex, Peter J.

2017-01-01

Although we perceive a richly detailed visual world, our ability to identify individual objects is severely limited in clutter, particularly in peripheral vision. Models of such “crowding” have generally been driven by the phenomenological misidentifications of crowded targets: using stimuli that do not easily combine to form a unique symbol (e.g. letters or objects), observers typically confuse the source of objects and report either the target or a distractor, but when continuous features are used (e.g. orientated gratings or line positions) observers report a feature somewhere between the target and distractor. To reconcile these accounts, we develop a hybrid method of adjustment that allows detailed analysis of these multiple error categories. Observers reported the orientation of a target, under several distractor conditions, by adjusting an identical foveal target. We apply new modelling to quantify whether perceptual reports show evidence of positional uncertainty, source confusion, and featural averaging on a trial-by-trial basis. Our results show that observers make a large proportion of source-confusion errors. However, our study also reveals the distribution of perceptual reports that underlie performance in this crowding task more generally: aggregate errors cannot be neatly labelled because they are heterogeneous and their structure depends on target-distractor distance. PMID:28378781

7. Notation Confusion of Symmetry Species for Molecules with Several Large-Amplitude Internal Motions

Groner, P.

2011-06-01

The Mulliken convention has become the standard notation for symmetry species (irreducible representations) of point groups for quasi-rigid molecules. No such convention exists for symmetry species of symmetry groups for semi-rigid or non-rigid molecules with large amplitude internal motions (LAMs). As a result, we have a situation where we create notations in a do-it-yourself fashion or adopt them from the literature, sometimes even without proper reference to its derivation or to the character table on which it is based. This may be just a nuisance for those who are comfortable enough with group theory and molecular symmetry groups to figure "it" out, but it represents a real problem for everybody else. The notation confusion is illustrated with examples from the literature (both old and new) on molecules with two or more LAMs. Most authors use the notation introduced by Myers and Wilson for molecules such as acetone or propane. No universal notation is in use for molecules with two methyl groups but lower overall symmetry. For example, the notation G_1_8 is used for one of these groups. As it turns out, different people use the same notation for different groups. This presentation is an attempt to bring some light into the dark and to combat confusion with a call for an anti-confusion convention. R. S. Mulliken, Phys. Rev. 43, 279 (1933). R. J. Myers, E. B. Wilson, J. Chem. Phys. 33, 186 (1960).

8. Derivation of Color Confusion Lines for Pseudo-Dichromat Observers from Color Discrimination Thresholds

PubMed Central

Matsudaira, Kahiro; Shinoda, Hiroyuki; Rattanakasemsuk, Kitiroj; Yamaguchi, Hideki

2011-01-01

The objective is to develop a method of defining color confusion lines in the display RGB color space through color discrimination tasks. In the experiment, reference and test square patches were presented side by side on a CRT display. The subject's task is to set the test color where the color difference from the reference is just noticeable to him/her. In a single trial, the test color was only adjustable along one of 26 directions around the reference. Thus 26 colors with just noticeable difference (JND) were obtained and made up a tube-like or an ellipsoidal shape around each reference. With color-anomalous subjects, the major axes of these shapes should be parallel to color confusion lines that have a common orientation vector corresponding to one of the cone excitation axes L, M, or S. In our method, the orientation vector was determined by minimizing the sum of the squares of the distances from JND colors to each confusion line. To assess the performance the method, the orientation vectors obtained by pseudo-dichromats (color normal observers with a dichromat simulator) were compared to those theoretically calculated from the color vision model used in the simulator.

9. Semantic confusion regarding the development of multisensory integration: a practical solution

PubMed Central

Stein, Barry E.; Burr, David; Constantinidis, Christos; Laurienti, Paul J.; Meredith, M. Alex; Perrault, Thomas J.; Ramachandran, Ramnarayan; Röder, Brigitte; Rowland, Benjamin A.; Sathian, K.; Schroeder, Charles E.; Shams, Ladan; Stanford, Terrence R.; Wallace, Mark T.; Yu, Liping; Lewkowicz, David J.

2011-01-01

There is now a good deal of data from neurophysiological studies in animals and behavioral studies in human infants regarding the development of multisensory processing capabilities. Although the conclusions drawn from these different datasets sometimes appear to conflict, many of the differences are due to the use of different terms to mean the same thing and, more problematic, the use of similar terms to mean different things. Semantic issues are pervasive in the field and complicate communication among groups using different methods to study similar issues. Achieving clarity of communication among different investigative groups is essential for each to make full use of the findings of others, and an important step in this direction is to identify areas of semantic confusion. In this way investigators can be encouraged to use terms whose meaning and underlying assumptions are unambiguous because they are commonly accepted. Although this issue is of obvious importance to the large and very rapidly growing number of researchers working on multisensory processes, it is perhaps even more important to the non-cognoscenti. Those who wish to benefit from the scholarship in this field but are unfamiliar with the issues identified here are most likely to be confused by semantic inconsistencies. The current discussion attempts to document some of the more problematic of these, begin a discussion about the nature of the confusion and suggest some possible solutions. PMID:20584174

10. Productive confusions: learning from simulations of pandemic virus outbreaks in Second Life

Cárdenas, Micha; Greci, Laura S.; Hurst, Samantha; Garman, Karen; Hoffman, Helene; Huang, Ricky; Gates, Michael; Kho, Kristen; Mehrmand, Elle; Porteous, Todd; Calvitti, Alan; Higginbotham, Erin; Agha, Zia

2011-03-01

Users of immersive virtual reality environments have reported a wide variety of side and after effects including the confusion of characteristics of the real and virtual worlds. Perhaps this side effect of confusing the virtual and real can be turned around to explore the possibilities for immersion with minimal technological support in virtual world group training simulations. This paper will describe observations from my time working as an artist/researcher with the UCSD School of Medicine (SoM) and Veterans Administration San Diego Healthcare System (VASDHS) to develop trainings for nurses, doctors and Hospital Incident Command staff that simulate pandemic virus outbreaks. By examining moments of slippage between realities, both into and out of the virtual environment, moments of the confusion of boundaries between real and virtual, we can better understand methods for creating immersion. I will use the mixing of realities as a transversal line of inquiry, borrowing from virtual reality studies, game studies, and anthropological studies to better understand the mechanisms of immersion in virtual worlds. Focusing on drills conducted in Second Life, I will examine moments of training to learn the software interface, moments within the drill and interviews after the drill.

11. Minimizing Confusion and Disorientation: Cognitive Support Work in Informal Dementia Caregiving

PubMed Central

Berry, Brandon

2015-01-01

Drawing from ethnographic fieldwork and in-depth interviews, I explain how informal dementia caregivers attempt to reduce the affected individual’s moments of confusion and disorientation through cognitive support work. I identify three stages through which such support takes shape and then gradually declines in usage. In a first stage, family members collaborate with affected individuals to first identify and then to avoid “triggers” that elicit sudden bouts of confusion. In a second stage, caregivers lose the effective collaboration of the affected individual and begin unilateral attempts to minimize confused states through pre-emptive conversational techniques, third-party interactional support, and social-environment shifts. In a third stage, caregivers learn that the affected individual has reached a level of impairment that does not respond well to efforts at reduction and begin abandoning strategies. I identify the motivations driving cognitive support work and discuss the role of lay health knowledge in dementia caregiving. I conclude by considering the utility of cognitive support as a concept within dementia caregiving. PMID:24984915

12. Quantitative, dynamic and noninvasive determination of skeletal muscle perfusion in mouse leg by NMR arterial spin-labeled imaging.

PubMed

Bertoldi, Didier; Loureiro de Sousa, Paulo; Fromes, Yves; Wary, Claire; Carlier, Pierre G

2008-11-01

Because mouse may relatively easily be genetically tailored to develop equivalent of human muscular diseases or to present controlled alterations of mechanisms involved in vasoregulation, it has become the prevalent species to explore such questions. However, the very small size of the animals represents a serious limitation when evaluating the functional consequences of these genetic manipulations. In this context, the recourse to arterial spin labeling (ASL) nuclear magnetic resonance (NMR) methods in which arterial water spins act as an endogenous and freely diffusible tracer of perfusion is tempting but challenging. This article shows that despite the small size of the animal, mouse muscle perfusion may be measured, at rest and in conditions of reactive hyperemia, using saturation inversion recovery sequence, a pulsed ASL variant, combined with NMR imaging. Baseline perfusion values in the mouse leg were 17+/-11 ml.min(-1).100 g(-1) (n=11) and were comparable to microsphere data from the literature. Under ischemia, leg perfusion was 1.2+/-9.3 ml.min(-1).100 g(-1) (n=11). The difference observed between basal and ischemic measurements was statistically different (P=.0001). The temporal pattern of hyperemia in mouse muscle was coherent with previously published measurements in humans and in rats. The mean peak perfusion was 62+/-24 ml.min(-1).100 g(-1) (n=6) occurring 48+/-27 s after the end of occlusion. In conclusion, this study demonstrated the ability of ASL combined to NMR imaging to quantify skeletal muscle perfusion in mice legs, both at rest and dynamically.

13. Computed Tomography Perfusion, Magnetic Resonance Imaging, and Histopathological Findings After Laparoscopic Renal Cryoablation: An In Vivo Pig Model.

PubMed

Nielsen, Tommy Kjærgaard; Østraat, Øyvind; Graumann, Ole; Pedersen, Bodil Ginnerup; Andersen, Gratien; Høyer, Søren; Borre, Michael

2017-08-01

The present study investigates how computed tomography perfusion scans and magnetic resonance imaging correlates with the histopathological alterations in renal tissue after cryoablation. A total of 15 pigs were subjected to laparoscopic-assisted cryoablation on both kidneys. After intervention, each animal was randomized to a postoperative follow-up period of 1, 2, or 4 weeks, after which computed tomography perfusion and magnetic resonance imaging scans were performed. Immediately after imaging, open bilateral nephrectomy was performed allowing for histopathological examination of the cryolesions. On computed tomography perfusion and magnetic resonance imaging examinations, rim enhancement was observed in the transition zone of the cryolesion 1week after laparoscopic-assisted cryoablation. This rim enhancement was found to subside after 2 and 4 weeks of follow-up, which was consistent with the microscopic examinations revealing of fibrotic scar tissue formation in the peripheral zone of the cryolesion. On T2 magnetic resonance imaging sequences, a thin hypointense rim surrounded the cryolesion, separating it from the adjacent renal parenchyma. Microscopic examinations revealed hemorrhage and later hemosiderin located in the peripheral zone. No nodular or diffuse contrast enhancement was found in the central zone of the cryolesions at any follow-up stage on neither computed tomography perfusion nor magnetic resonance imaging. On microscopic examinations, the central zone was found to consist of coagulative necrosis 1 week after laparoscopic-assisted cryoablation, which was partially replaced by fibrotic scar tissue 4 weeks following laparoscopic-assisted cryoablation. Both computed tomography perfusion and magnetic resonance imaging found the renal collecting system to be involved at all 3 stages of follow-up, but on microscopic examination, the urothelium was found to be intact in all cases. In conclusion, cryoablation effectively destroyed renal parenchyma

14. Measurement of ventilation- and perfusion-mediated cooling during laser ablation in ex vivo human lung tumors.

PubMed

Vietze, Andrea; Koch, Franziska; Laskowski, Ulrich; Linder, Albert; Hosten, Norbert

2011-11-01

Perfusion-mediated tissue cooling has often been described in the literature for thermal ablation therapies of liver tumors. The objective of this study was to investigate the cooling effects of both perfusion and ventilation during laser ablation of lung malignancies. An ex vivo lung model was used to maintain near physiological conditions for the specimens. Fourteen human lung lobes containing only primary lung tumors (non-small cell lung cancer) were used. Laser ablation was carried out using a Nd:YAG laser with a wavelength of 1064 nm and laser fibers with 30 mm diffusing tips. Continuous invasive temperature measurement in 10 mm distance from the laser fiber was performed. Laser power was increased at 2 W increments starting at 10 W up to a maximum power of 12-20 W until a temperature plateau around 60 °C was reached at one sensor. Ventilation and perfusion were discontinued for 6 min each to assess their effects on temperature development. The experiments lead to 25 usable temperature profiles. A significant temperature increase was observed for both discontinued ventilation and perfusion. In 6 min without perfusion, the temperature rose about 5.5 °C (mean value, P<0.05); without ventilation it increased about 7.0 °C (mean value, P<0.05). Ventilation- and perfusion-mediated tissue cooling are significant influencing factors on temperature development during thermal ablation. They should be taken into account during the planning and preparation of minimally invasive lung tumor treatment in order to achieve complete ablation. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

15. Developing a Benchmarking Process in Perfusion: A Report of the Perfusion Downunder Collaboration

PubMed Central

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

2012-01-01

Abstract: 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 pCO2 management during cardiopulmonary bypass. The values chosen for each QI were: blood glucose ≥4 mmol/L and ≤10 mmol/L; arterial outlet temperature ≤37°C; and arterial blood gas pCO2 ≥ 35 and ≤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. PMID:22730861

16. 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. © 2016 Elsevier B.V. All rights reserved.

17. Magnetic Resonance Imaging of Ventilation and Perfusion in the Lung

NASA Technical Reports Server (NTRS)

Prisk, Gordon Kim (Inventor); Hopkins, Susan Roberta (Inventor); Buxton, Richard Bruce (Inventor); Pereira De Sa, Rui Carlos (Inventor); Theilmann, Rebecca Jean (Inventor); Cronin, Matthew Vincent (Inventor)

2017-01-01

Methods, devices, and systems are disclosed for implementing a fully quantitative non-injectable contrast proton MRI technique to measure spatial ventilation-perfusion (VA/Q) matching and spatial distribution of ventilation and perfusion. In one aspect, a method using MRI to characterize ventilation and perfusion in a lung includes acquiring an MR image of the lung having MR data in a voxel and obtaining a breathing frequency parameter, determining a water density value, a specific ventilation value, and a perfusion value in at least one voxel of the MR image based on the MR data and using the water density value to determine an air content value, and determining a ventilation-perfusion ratio value that is the product of the specific ventilation value, the air content value, the inverse of the perfusion value, and the breathing frequency.

18. Reversible ventilation and perfusion abnormalities in unilateral obstructed lung

SciTech Connect

Ward, H.E.; Jones, R.L.; King, E.G.; Sproule, B.J.; Fortune, R.L.

1982-01-01

An intraluminal carcinoid tumor obstructing the left mainstem bronchus produced hypoxemia through alteration in ventilation/perfusion matching. Studies of regional lung function using 133-xenon (/sup 133/Xe) and a multiprobe computerized instrumentation system documented a reduction of perfusion to 22 percent and ventilation to 6 percent of the total. There was negligible washout of intravenously injected /sup 133/Xe from the left lung consistent with air trapping. Four days after left mainstem bronchial sleeve resection, perfusion, ventilation and washout of injected xenon had significantly improved and by four months postresection, all measurements were virtually normal, although complete restoration of perfusion in relation to ventilation was delayed. Regional lung function studied with a multiprobe system in this patient provided a clinical model for the study of ventilation and perfusion inter-relationships in large airway obstruction and demonstrated that a prolonged time may be required for return of perfusion to normal.

19. DIFFUSION PUMP

DOEpatents

Levenson, L.

1963-09-01

A high-vacuum diffusion pump is described, featuring a novel housing geometry for enhancing pumping speed. An upright, cylindrical lower housing portion is surmounted by a concentric, upright, cylindrical upper housing portion of substantially larger diameter; an uppermost nozzle, disposed concentrically within the upper portion, is adapted to eject downwardly a conical sheet of liquid outwardly to impinge upon the uppermost extremity of the interior wall of the lower portion. Preferably this nozzle is mounted upon a pedestal rising coaxially from within the lower portion and projecting up into said upper portion. (AEC)

20. Is there more valuable information in PWI datasets for a voxel-wise acute ischemic stroke tissue outcome prediction than what is represented by typical perfusion maps?