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PubMed2006

Attributable mortality of Acinetobacter baumannii infections in critically ill patients: a systematic review of matched cohort and case-control studies.

INTRODUCTION: There has been a continuing controversy about whether infection with Acinetobacter baumannii increases morbidity and mortality independently of the effect of other confounding factors. METHODS: We performed a systematic review of matched case-control and cohort studies examining the mortality attributable to infection with or acquisition of A. baumannii (infection or colonization). We included in our review studies that compared mortality and/or morbidity of patients with acquisition of or infection with A. baumannii (cases) with the outcomes of matched patients without A. baumannii isolation from clinical specimens (controls). The relevant studies were identified from searches of the PubMed and the Cochrane Library databases. Two independent reviewers performed the literature search, study selection, and data extraction from nine identified relevant studies. RESULTS: The attributable mortalities, in the hospital and in the intensive care unit, of patients with A. baumannii infection in six matched case-control studies included in our review ranged from 7.8% to 23% and from 10% to 43%, respectively. In addition, a statistically significantly higher mortality was reported for patients with A. baumannii acquisition; that is, colonization or infection (cases) compared with controls without such an acquisition in all four reviewed studies that reported data on this comparison. CONCLUSION: Although definitive statements about the mortality attributable to the acquisition of A. baumannii cannot be made from the available studies because of their methodological heterogeneity, the reviewed data suggest that infection with or acquisition of A. baumannii seems to be associated with increased mortality.

Acinetobacter Infections↗
PubMed1994

Incremental evaluation of exercise capacity as an independent predictor of coronary artery disease presence and extent.

To determine the independent incremental value of exercise capacity (METS) concerning the presence and extent of coronary artery disease, we analyzed data from 800 patients with suspected coronary disease who underwent both exercise testing and coronary angiography. We performed logistic regression analysis of clinical and exercise test data with an incremental design to mimic the usual flow of data acquisition. Separate analyses were performed concerning coronary disease presence (> or = 1 vessel with a > or = 50% lesion) and extent (three-vessel/left main disease). Diagnostic accuracy was determined by calculating receiver operating characteristic (ROC) curve areas. When considered alone, METS was a significant predictor of both presence and extent of disease. Multivariate analysis revealed that METS was an independent predictor of disease extent but not presence. However, comparison of ROC curve areas failed to show any loss of accuracy when METS was removed from the coronary disease extent analysis. Despite the strong univariate relationship between exercise capacity and coronary disease presence and extent and the independence of exercise capacity as a predictor of coronary disease extent, the lack of an additional incremental accuracy attributed to its consideration virtually cancels its value as a diagnostic variable for assessing both coronary disease presence and extent.

Adult↗
PubMed2007

Pulmonary MR perfusion at 3.0 Tesla using a blood pool contrast agent: Initial results in a swine model.

PURPOSE: To prospectively evaluate the technical feasibility of a highly accelerated pulmonary MR perfusion protocol at 3.0T using a blood pool contrast agent in a swine model. MATERIALS AND METHODS: Twelve pigs underwent time-resolved pulmonary MR angiography (MRA) on a 3.0T MR system under anesthesia and controlled mechanical ventilation. After intravenous injection of 0.05 mmol/kg of Gadomer-17 at 4 mL/second, a fast time-resolved MRA sequence with temporal echo-sharing (three segmented k-space) and highly accelerated parallel acquisition was used to acquire 3D data sets with an in-plane resolution of 1 x 1 mm(2) (slice thickness = 6 mm) and temporal resolution of one second. Image quality was evaluated independently by two radiologists, and quantitative analysis of perfusion parameters was performed using pre-released perfusion software. RESULTS: All studies were identified by both readers as having diagnostic image quality (range = 2-3, median = 3) and there was excellent interobserver agreement (kappa = 0.89; 95% CI = 0.83, 0.95). A quantitative analysis of perfusion indices was performed, with excellent overall goodness-of-fit (chi(2) value = 1.4, degree of freedom (DF) = 1). Successfully derived perfusion parameters included the time to peak (TTP, 5.1 +/- 0.7 second), mean transit time (MTT, 6.6 +/- 0.9 second), maximal signal intensity (MSI, 1051.2 +/- 718.9 arbitrary units [A.U.]), and maximal upslope of the curve (MUS, 375.9 +/- 263.4 A.U./second). CONCLUSION: 3.0T pulmonary MR perfusion using a blood pool contrast agent in a swine model is feasible. The higher available signal-to-noise ratio (SNR) at 3.0T and the high T1 relaxivity of Gadomer-17 effectively support highly accelerated parallel acquisition, and improve the performance of time-resolved pulmonary MRA.

Animals↗
PubMed1996

The effects of melanocortin peptides and corticosterone on habituation in the great plains toad, Bufo cognatus.

We investigated the ability of various melanocortin peptides and corticosterone to influence habituation of prey-catching behavior in the toad, Bufo cognatus. Male toads were injected with various melanocortin peptide fragments or corticosterone 30 min prior to acquisition. Adrenocorticotropin (ACTH[1-39]), ACTH[4-10], and N-acetyl ACTH[1-13] amide (alpha-MSH) significantly decreased the number of turning reactions during acquisition in relation to controls. The effects of the noncorticotropic ACTH fragments were rapid and transient, occurring within the first 20 min of acquisition. Corticosterone caused a slight but significant decrease in the number of turning reactions. Neither des-acetyl alpha-MSH nor (Nle4, D-Phe7) alpha-MSH had any effect on acquisition. ACTH[1-39] was the only peptide that delayed extinction. The ability of alpha-MSH to facilitate acquisition was not observed in the presence of the alpha-MSH antagonist U-76188E. These data suggest that the effects of ACTH on habituation are, in part, independent of effects on glucocorticoid secretion. Apparently, similar structural requirements are necessary for the behavioral effects of melanocortins in amphibians and mammals.

Adrenocorticotropic Hormone↗
PubMed2004

[Rapid prototyping in planning reconstructive surgery of the head and neck. Review and evaluation of indications in clinical use].

PURPOSE: The aim was to define the indications for use of rapid prototyping models based on data of patients treated with this technique. PATIENTS AND METHODS: Since 1987 our department has been developing methods of rapid prototyping in surgery planning. During the study, first the statistical and reproducible anatomical precision of rapid prototyping models was determined on pig skull measurements depending on CT parameters and method of rapid prototyping. RESULTS: Measurements on stereolithography models and on selective laser sintered models confirmed an accuracy of +/-0.88 mm or 2.7% (maximum deviation: -3.0 mm to +3.2 mm) independently from CT parameters or method of rapid prototyping, respectively. With the same precision of models multilayer helical CT with a higher rate is the preferable method of data acquisition compared to conventional helical CT. From 1990 to 2002 in atotal of 122 patients, 127 rapid prototyping models were manufactured: in 112 patients stereolithography models, in 2 patients an additional stereolithography model, in 2 patients an additional selective laser sinter model, in 1 patient an additional milled model, and in 10 patients just a selective laser sinter model. CONCLUSION: Reconstructive surgery, distraction osteogenesis including midface distraction, and dental implantology are proven to be the major indications for rapid prototyping as confirmed in a review of the literature. Surgery planning on rapid prototyping models should only be used in individual cases due to radiation dose and high costs. Routine use of this technique only seems to be indicated in skull reconstruction and distraction osteogenesis.

Computer Graphics↗
PubMed1989

Multicentre European trials: their design, execution and relevance.

Multicentre randomized clinical trials in Europe over the past decade have made a major contribution to the practice of cardiology and will increasingly do so when the Single Europe Act becomes a fact of life in 1992. The arguments for independent scientifically based research organizations and their role in the area of coronary artery disease are outlined. These include cost-benefit considerations, the science of clinical trials, data acquisition techniques and data management requirements. The role of the pharmaceutical industry in relation to the investigator-trialist is discussed. A critique of the current fashion 'Big is beautiful', with arguments against 'simplicity' and 'large size' and the need for 'credibility' is provided. Applicability of data from trials and their economic usefulness and validity in terms of sound pathophysiological hypotheses are also discussed and illustrated by using the CABRI trial as an example.

Angioplasty, Balloon, Coronary↗
PubMed1989

Twin channel infrared optometer for recording binocular accommodation.

A twin channel infrared (IR) optometer for recording accommodation from each eye is described. Some modifications to a conventional single channel optometer design are necessary to facilitate binocular recording. The optometer incorporates an on-line microcomputer for data acquisition and processing. Processing includes power spectrum and correlation analysis, and a facility for performing cursor controlled measurement of time delays. Accommodation responses recorded are shown to be independent of horizontal eye movements, and little affected by the drug used for mydriasis.

Accommodation, Ocular↗
PubMed1984

Explososcan: a parallel processing technique for high speed ultrasound imaging with linear phased arrays.

The data acquisition rate in medical ultrasonic imaging devices is limited by the acoustic propagation velocity in the tissues. Typically in such machines the image lines are produced sequentially one line per transmitted pulse. A parallel processing scheme has been implemented which enables the data acquisition rate to increase by a factor of four through the simultaneous acquisition of four B-mode image lines from each individual broadened transmit pulse. The higher data rate can be used to increase the image frame rate to produce independent images that can be averaged in the image frame to reduce noise, or to produce a conventional image at standard video frame rates while reducing patient exposure. Alternatively, the field of view can be increased over that of a normal scan without sacrificing frame rate. These advantages are achieved with little reduction in the measured resolution. The design and performance of this device are described. A sample in vivo image is included.

Acoustics↗
PubMed1990

Soluble and surface-bound immunoglobulin triggers human monocyte activation and hydrogen peroxide release.

Human mononuclear phagocytes (MO) can mediate the destruction of a variety of foreign and tumor target cells. In most circumstances, however, peripheral blood MO are noncytotoxic and must acquire cytotoxic activity. To investigate the cell surface molecules that participate in the acquisition of MO-mediated cytotoxicity, we used a panel of monoclonal antibodies (MAbs) recognizing a variety of membrane molecules. MAbs to eight different MO surface molecules did not trigger the killing of tumor target cells. To determine if these cell surface molecules triggered an activated but incomplete lytic mechanism, the ability of these molecules to trigger hydrogen peroxide (H2O2) release was assessed. Several MAbs triggered H2O2 release from MO isolated from the peripheral blood. The pattern of MAb-triggered H2O2 release correlated not with the MO surface antigen, but with the immunoglobulin (Ig) isotype. Isotype-specific H2O2 release was abrogated with the enzymatic removal of the Fc portion of the Ig and enhanced by interferon-gamma pretreatment, indicating that the membrane signal was mediated by cell surface Fc receptors. H2O2 release was independent of the presentation of the Ig molecule. Comparable H2O2 release was observed whether the Ig was in surface-bound or soluble form. These data support an important role for Fc receptors in the acquisition of cytotoxic potential by human MO.

Antibodies, Monoclonal↗
PubMed2006

Collimator selection, acquisition speed, and visual assessment of 131I-tositumomab biodistribution in a phantom model.

UNLABELLED: (131)I-Tositumomab has been used in treating patients with non-Hodgkin's lymphoma. It is generally recommended that high-energy collimators be used to image patients before they receive (131)I-tositumomab therapy, to determine the effective half-life for therapeutic dose and gross biodistribution. Because many nuclear medicine departments do not possess high-energy collimators, this study was designed to assess the suitability of using medium-energy collimators. The effect of scanning speed was also investigated, in an attempt to optimize the acquisition time. METHODS: Measurements were taken using an elliptic anthropomorphic torso phantom and an organ-scanning phantom fitted with fillable spheres (1-5 cm in diameter) and organ inserts. Three phantom studies were performed with differing initial (131)I concentrations in the organs, the spheres, and the thoracic and abdominal chambers. Images were acquired with both high-energy and medium-energy collimators and at acquisition speeds of 20 and 100 cm/min. The half-life for each combination (study/collimator/speed) was calculated from a linear fit of the data. The contrast of the tumor sphere was assessed using 2 identical regions, placed on and beside the sphere, and averaged over several time points. Biodistribution and image quality were visually assessed by 2 independent observers. RESULTS: Measured half-life values and visual assessment of biodistribution showed no significant difference between the 2 collimators (P = 0.32) or acquisition speeds (P = 0.85). A significant difference in the contrast of the tumor spheres was observed between the 2 collimators (P < 0.01) but not between acquisition speeds. Visual assessment of the images showed increased noise on the image acquired at 100 cm/min, although this noise did not affect lesion detectability. CONCLUSION: Measured half-life is not significantly different between the 2 collimators; hence, calculation of the residence time would be nearly the same. Medium-energy collimators can be used to accurately calculate the (131)I-tositumomab therapeutic dose and detect alterations in biodistribution.

Antibodies, Monoclonal↗
PubMed1994

Growth and intestinal differentiation are independently regulated in HT29 colon cancer cells.

The polar-planar compound hexamethylene bisacetamide (HMBA) can inhibit HT29 colon carcinoma cell growth and induce a more benign phenotype, as defined by decreased anchorage-independent clonogenicity, loss of a cell surface malignancy marker, and decreased in vivo tumorigenicity. The principle aim of this study was to determine whether HMBA's effects on HT29 cell growth and biologic behavior correlate with effects on intestinal differentiation. Parallel studies were performed with sodium butyrate (NaBT), a potent inducer of intestinal differentiation. HT29 cell growth, proliferation, and markers of intestinal differentiation were assayed after short- and long-term treatment with HMBA, NaBT, or the combination. Both 5 mM HMBA and 5 mM NaBT were potent inhibitors of monolayer growth; in combination their effects were nearly additive. Inhibition of DNA synthesis was detectable within 6 h of treatment and was preceded by down-regulation of c-myc expression. Soft agar clonogenicity was also decreased by 90%, > 99%, and > 99% by HMBA, NaBT, and the combination, respectively. Despite these parallel effects on growth and in vitro markers of a benign phenotype, effects on intestinal differentiation were discordant. NaBT induced significant increases in membrane-associated alkaline phosphatase activity, cytosolic mucin content, PAS+/diastase-resistant cells, and ultrastructural evidence of intestinal cell differentiation. HMBA not only failed to induce markers of intestinal differentiation, but attenuated NaBT's effects when used in combination. These data suggest that growth and intestinal differentiation may be independently regulated in HT29 cells. They also suggest that expression of intestinal markers of differentiation is not a prerequisite for the acquisition of a more benign phenotype.

Acetamides↗
PubMed2002

Independent component analysis applied to diffusion tensor MRI.

The accuracy of the outcome in a diffusion tensor imaging (DTI) experiment depends on the acquisition scheme as well as the postprocessing methods used. In the present study, the DTI results acquired after applying different combinations of diffusion-weighted (DW) gradient orientations were initially compared. Then, spatially independent component analysis (ICA) was applied to the T(2) and DW images. In all cases a single component was detected that was similar to the map of the trace of the diffusion tensor, but contained a reduced amount of noise. Furthermore, when no correction for eddy current artifacts was used in the image acquisition scheme, the effects of eddy currents were separated by ICA into independent components. After these components were removed, conventional estimation of the diffusion tensor was performed on the modified data. No artifact was contained in the final rotationally invariant scalar quantities that describe the intrinsic diffusion properties. Additionally, independent components that mapped major white matter fiber tracts in the human brain were identified. Finally, the noise included in the original T(2) and DW images was also separated by ICA into independent components. These components were subsequently removed and a reduction of noise in the final DTI results was achieved.

Adult↗
PubMed2004

Discrimination of olives according to fruit quality using Fourier transform Raman spectroscopy and pattern recognition techniques.

Fourier transform Raman spectroscopy combined with pattern recognition has been used to discriminate olives of different qualities. They included samples of sound olives, olives with frostbite, olives that have been collected from the ground, fermented olives, and olive samples with diseases. Milled olives were measured in a dedicated sample cup, which was rotated during spectrum acquisition. A preliminary study of the data set structure was performed using hierarchical cluster analysis and principal component analysis. Two supervised pattern recognition techniques, K-nearest neighbors and soft independent modeling of class analogy (SIMCA), were tested using a "leave-a-fourth-out" cross-validation procedure. SIMCA provided the best results, with prediction abilities of 95% for sound, 93% for frostbite, 96% for ground, and 92% for fermented olives. The olive samples with diseases (too few to define a class) were included in the validation and recognized as not belonging to any class. None of the damaged olive samples was wrongly predicted to the class of sound olives. With this approach a selection of sound olives for the production of high-quality virgin olive oil can be achieved.

Fourier Analysis↗
PubMed1994

The use of ultrasound mean acoustic attenuation to quantify bone formation during distraction osteogenesis performed by the Ilizarov method. Preliminary results in five dogs.

RATIONALE AND OBJECTIVES: Management of distraction during Ilizarov limb lengthening remains primarily clinical and empirical. Estimates of tissue acoustic attenuation were evaluated for their ability to quantify bone formation within the distraction gap. METHODS: Five dogs had tibias lengthened by the method of Ilizarov. Mean acoustic attenuation measurements at multiple positions across the distraction gap were compared with corresponding x-ray computed tomography attenuation measurements. RESULTS: Computed tomography and ultrasound attenuation displayed similar quantitative behavior across the gap. Linear correlation between them ranged from R2 = .878 to R2 = .131. Fibrous interzone width estimates based on computed tomography and ultrasound attenuation measurements were correlated, based on our preliminary data with R2 = .519. These estimates are independent of the width of distraction. CONCLUSIONS: Ultrasound parallels computed tomography as a measure of bone formation within the distraction gap. Future studies are needed to improve acoustic attenuation data acquisition techniques and to evaluate their potential as a tool for optimizing early distraction rates in patients at risk for rate-related complications.

Acoustics↗
PubMed1998

Studies of acute ischemic stroke with proton magnetic resonance spectroscopy: relation between time from onset, neurological deficit, metabolite abnormalities in the infarct, blood flow, and clinical outcome.

BACKGROUND AND PURPOSE: Proton magnetic resonance spectroscopy (MRS) can be used to study metabolite abnormalities in the brains of stroke patients. We have used it to examine the relations between the metabolites in the infarct (N-acetylaspartate [NAA] and lactate) and the time lapse from stroke to MRS, the presenting neurological deficit, infarct size and swelling (on MRI), blood flow to the infarct (estimated by transcranial Doppler ultrasound), and clinical outcome. METHODS: Patients with symptoms of a moderate to large cortical infarct underwent serial proton MRS (Siemens 1.5 Magnetom) within 4 days, from 5 to 10, and from 11 to 35 days after the stroke. A long echo time PRESS single voxel or chemical shift imaging acquisition was used. Transcranial Doppler ultrasound was performed daily in the first week and twice per week thereafter until the final MRS. Clinical features and baseline demographic data were collected independently by a stroke physician and 6-month outcome by postal questionnaire. RESULTS: Fifty patients underwent at least 1 MRS examination. Reduced NAA in the infarct within the first 4 days was related to the clinical stroke syndrome, more extensive infarction, more severely reduced blood supply to the infarct, and the presence of lactate. The presence of lactate was related to large infarcts and reduced NAA. Swelling in the infarct was most closely associated with large infarcts and reduced blood supply but not reduced NAA or the presence of lactate. Clinical outcome was most closely related to the extent of the infarct (more than to the clinical syndrome)--the larger the infarct the worse the outcome--but not to the metabolite concentrations alone. CONCLUSIONS: The reduction in NAA (but not the presence of lactate) in a visible infarct was related to the reduction in blood flow to the infarct, which in turn was related to infarct extent and clinical outcome.

Acute Disease↗
PubMed2006

Reliability and validity of bilateral thigh and foot accelerometry measures of walking in healthy and hemiparetic subjects.

OBJECTIVE: Measures of walking ability in large clinical trials are usually limited to a timed short-distance walk and the distance walked in a fixed time. A new integrated system of 5 accelerometers was tested for reliability and compared to a footswitch system to determine if the accelerometers offered a practical option for the acquisition of spatiotemporal gait parameters. METHODS: Leg accelerations and decelerations were defined in relation to simultaneous kinematic and electromyographic data acquired from a healthy subject. Eight healthy adults and 6 independent ambulators with hemiparetic stroke walked 15 m at 2 different speeds wearing both the accelerometers and footswitches. Twelve healthy subjects walked at 5 different speeds repeated 3 times on each of 2 days wearing the accelerometers. Walking speed, cadence, stride length, and single- and double-limb support, swing, and stance times were calculated. RESULTS: No differences (t test, P > 0.2) were found between footswitch and accelerometer variables when comparing all left or right legs in healthy subjects and all paretic or unaffected legs in stroke subjects. A 2-way nested ANOVA model (speed, left and right legs, trial, and session) with the accelerometers at walking speeds from 0.5 to 1.8 m/s revealed high reproducibility of all measures. CONCLUSIONS: The accelerometry system provided reliable and valid spatiotemporal measures of gait for the upper range of speeds likely to be targeted for rehabilitation interventions in ambulatory subjects.

Acceleration↗
PubMed1979

A practical application of computer pattern recognition research: the Abbott ADC-500 differential classifier.

The ADC-500 is a new blood cell differential classifier manufactured by Abbott Laboratories. It performs 500-cell leukocyte differentials on both normal and abnormal cells, evaluates red cell morphology and estimates platelet sufficiency at a rate of 40 to 50 samples per hour in stand-alone operation. The ADC-500 system consists of a spinner which prepares a uniform blood monolayer on a slide, a stainer which reproducibly stains the slide with Wright's stain, an encoder which attaches an instrument and human readable identification to the slide and an analyzer which accepts a stack of up to 50 slides, evaluates these slides and prints the results and the slide identification on report forms. The system's analysis rate, which represents a 5- to 10-fold increase over other commercially available differential counters, requires a number of specialized techniques for its realization. One key to this performance is the development of a high speed X-Y slide positioning stage which can move to a new cell and settle in 50 msec. Another is the high degree of parallelism used in the system structure and the pipelining of the data processing. A third is the development of uniform and repeatable sample preparation modules. Within the analyzer module, the autofocus, white cell acquisition and high resolution cell analysis systems are independent and operate in parallel. At the same time within the high resolution cell analysis system, one cell is acquired; the digitized image of a second processed; and a third is classified using pattern recognition techniques. All of these tasks, except focus, are under the control of a minicomputer system. Tests of the system reveal good accuracy and an improvement in precision due to the increase in the number of counted cells.

Blood Cells↗
PubMed1993

Acquisition of hormone-independent growth in MCF-7 cells is accompanied by increased expression of estrogen-regulated genes but without detectable DNA amplifications.

A hormone-independent but hormone-responsive subpopulation (MCF7/MIII) of the hormone-dependent MCF-7 human breast cancer cell line (R. Clarke et al., Proc. Natl. Acad. Sci. USA 86: 3649-3653, 1989) was further passaged in ovariectomized nude mice and re-established in vitro as the continuous cell line MCF7/LCC1. The lag time to the appearance of proliferating tumors in ovariectomized animals is significantly reduced in MCF7/LCC1 when compared with MCF7/MIII cells. In gel denaturation/renaturation analysis of tumor, genomic DNA does not reveal significant differences in the pattern of detectable DNA amplifications between parent MCF-7 cells and MCF7/LCC1 cells. In the absence of estrogen, steady-state levels of phosphoinositol turnover are similar in both MCF-7 and MCF7/LCC1 cells, but turnover is increased by estrogen only in MCF-7 cells. MCF7/MIII and MCF7/LCC1, but not MCF-7 cells, express a high baseline level of the estrogen-regulated pS2 mRNA. The baseline level of expression of progesterone receptor protein, but not mRNA, is higher in MCF7/LCC1 when compared with either MCF-7 or early passage MCF7/MIII cells. However, while the estrogen receptor is also an estrogen-regulated gene, MCF7/MIII and MCF7/LCC1 cells retain estrogen receptor levels equivalent to the parental MCF-7 cells. These data indicate that progression to hormone independence can occur without major gene amplifications or a high constitutive induction of phosphoinositide metabolism. Thus, DNA amplifications may be acquired during the early initiation and/or promotional events of carcinogenesis. Significantly, acquisition of a hormone-independent but responsive phenotype in human breast cancer is associated with perturbations in the expression of specific estrogen-regulated genes.

Animals↗