共查询到20条相似文献,搜索用时 484 毫秒
1.
Quaternion-based strap-down integration method for applications of inertial sensing to gait analysis
Sabatini AM 《Medical & biological engineering & computing》2005,43(1):94-101
The proposed strap-down integration method exploits the cyclical nature of human gait: during the gait swing phase, the quaternion-based
attitude representation is integrated using a gyroscope from initial conditions that are determined during stance by an accelerometer.
Positioning requires double time integration of the gravity-compensated accelerometer signals during swing. An interpolation
technique applied to attitude quaternions was developed to improve the accuracy of orientation and positioning estimates by
accounting for the effect of sensor bias and scale factor drifts. A simulation environment was developed for the analysis
and testing of the proposed algorithm on a synthetic movement trajectory. The aim was to define the true attitude and positioning
used in the computation of estimation errors. By thermal modelling, the changes of bias and scale factor of the inertial sensors,
calibrated at a single reference temperature, were analysed over a range of ±10°C, for measurement noise standard deviations
up to σg = 2.5° s−1 (gyroscope) and σa = 0.05 m s−1 (accelerometer). The compensation technique reduced the maximum root mean square errors (RMSEs) to: RMSEθ=14.6° (orientation) and RMSEd=17.7 cm (positioning) for an integration interval of one gait cycle (an improvement of 3° and 7 cm); RMSEθ=14.8° and RMSEd=30.0 cm for an integration interval of two gait cycles (an improvement of 11° and 262 cm). 相似文献
2.
Schulte E Farina D Rau G Merletti R Disselhorst-Klug C 《Medical & biological engineering & computing》2003,41(3):338-345
The aim of the study was to compare experimentally conduction velocity (CV) estimates obtained with different estimation methods
based on surface electromyogram (EMG) signals detected using five spatial filters. The filters investigated were the longitudinal
single and double differential, transverse single and double differential, and normal double differential. The same surface
EMG signals detected as described in Part 1 were used in this work. CV was estimated with four commonly used delay estimation
techniques, i.e. from the distance between the peak values of two waveforms (with and without polynomial interpolation around
the peak), and by the maximum likelihood estimate (MLE) based on two or more surface EMG channels. The average standard deviation
of CV estimation (for all the MUs and the two muscles together) was 0.61 ms−1 and 0.79 ms−1 for the peak method, with and without interpolation, respectively, and 0.50ms−1 and 0.31 ms−1 for the MLE method, from two and more surface EMG channels, respectively. Moreover, the mean of CV estimates varied by as
much as 1 ms−1 depending on the spatial filter used and the method adopted for CV estimation. Considering the dependence on the spatial
filter only, the average (over all estimation methods) CV estimates obtained with the five spatial filters were 4.32 ms−1 (normal double differential), 4.23ms−1 (longitudinal double differential), 4.61 ms−1 (transverse double differential), 4.64ms−1 (transverse single differential) and 4.03 ms−1 (longitudinal single differential). It was concluded that the comparison of single MU CV values obtained in different studies
is critical if different spatial filters and processing techniques are used for their estimation. Higher estimates of CV were
attributed to a smaller reduction in non-travelling signal components and thus were assumed to be positively biased. 相似文献
3.
Spengler CM Knöpfli-Lenzin C Birchler K Trapletti A Boutellier U 《European journal of applied physiology》2000,81(5):368-374
The aim of the present study was to investigate whether the changes in breathing pattern that frequently occur towards the
end of exhaustive exercise (i.e., increased breathing frequency, f
b, with or without decreased tidal volume) may be caused by the respiratory work itself rather than by leg muscle work. Eight
healthy, trained subjects performed the following three sessions in random order: (A) two sequential cycling endurance tests
at 78% peak O2 consumption (V˙O2peak) to exhaustion (A1, A2); (B) isolated, isocapnic hyperpnea (B1) at a minute ventilation (V˙
E) and an exercise duration similar to that attained during a preliminary cycling endurance test at 78% V˙O2peak, followed by a cycling endurance test at 78% V˙O2peak (B2); (C) isolated, isocapnic hyperpnea (C1) at a V˙
E at least 20% higher than that of the preliminary cycling test and the same exercise duration as the preliminary cycling test,
followed by a cycling endurance test at 78% V˙O2peak (C2). Neither of the two isocapnic hyperventilation tasks (B1 or C1) affected either the breathing pattern or the endurance
times of the subsequent cycling tests. Only cycling test A2 was significantly shorter [mean (SD) 26.5 (8.3) min] than tests
A1 [41.0 (9.0) min], B2 [41.9 (6.0) min], and C2 [42.0 (7.5) min]. In addition, compared to test A1, only the breathing pattern
of test A2 was significantly different [i.e., V˙
E: +10.5 (7.6) l min−1, and f
b: +12.1 (8.5) breaths min−1], in contrast to the breathing patterns of cycling tests B2 [V˙
E: −2.5 (6.2) l min−1, f
b: +0.2 (3.6) breaths min−1] and C2 [V˙
E: −3.0 (7.0) l min−1, f
b: +0.6 (6.1) breaths min−1]. In summary, these results suggest that the changes in breathing pattern that occur towards the end of an exhaustive exercise
test are a result of changes in the leg muscles rather than in the respiratory muscles themselves.
Accepted: 7 October 1999 相似文献
4.
Grönlund C Ostlund N Roeleveld K Karlsson JS 《Medical & biological engineering & computing》2005,43(1):63-70
The paper presents a new approach for simultaneous estimation of muscle fibre conduction velocity (MFCV) and muscle fibre
orientation (MFO) for motor units (MUs) in two-dimensional (2D) multichannel surface electromyography recordings. This is
an important tool for detecting changes and abnormalities in muscle function and structure. In addition, simultaneous estimation
of MFO and MFCV avoids the necessity of manual electrode alignment. The proposed method detected propagating MU action potentials
(MUAPs) in a running time window as moving components in amplitude maps. Thereafter, estimations were obtained by fitting
a three-dimensional function to these maps. The performance was evaluated using synthetic MU signals at 10 dB SNR and authentic
biceps brachii measurements. Results demonstrated MFCV and MFO estimates with standard deviations of less than 0.05 m s−1 and 1° for simulated signals, and less than 0.2 m s−1 and 4° for experimental data. However, standard deviations as low as 0.12 m s−1 and 1.6° from real signals were demonstrated. It was concluded that the method performs as well as, or better than, linear
array multichannel methods when individual propagating MUAPs can be identified, even if electrodes are not aligned with fibre
direction. 相似文献
5.
Carey G 《Behavior genetics》2005,35(5):667-670
Introduced by C.R. Rao in 1945, the intraclass covariance matrix has seen little use in behavioral genetic research, despite
the fact that it was developed to deal with family data. Here, I reintroduce this matrix, and outline its estimation and basic
properties for data sets on pairs of relatives. The intraclass covariance matrix is appropriate whenever the research design
or mathematical model treats the ordering of the members of a pair as random. Because the matrix has only one estimate of
a population variance and covariance, both the observed matrix and the residual matrix from a fitted model are easy to inspect
visually; there is no need to mentally average homologous statistics. Fitting a model to the intraclass matrix also gives
the same log likelihood, likelihood-ratio (LR) χ2, and parameter estimates as fitting that model to the raw data. A major advantage of the intraclass matrix is that only two
factors influence the LR χ2—the sampling error in estimating population parameters and the discrepancy between the model and the observed statistics.
The more frequently used interclass covariance matrix adds a third factor to the χ2—sampling error of homologous statistics. Because of this, the degrees of freedom for fitting models to an intraclass matrix
differ from fitting that model to an interclass matrix. Future research is needed to establish differences in power—if any—between
the interclass and the intraclass matrix. 相似文献
6.
Castellani JW Armstrong LE Kenefick RW Pasqualicchio AA Riebe D Gabaree CL Maresh CM 《European journal of applied physiology》2001,84(1-2):42-47
It is yet unknown how upper body exercise combined with high ambient temperatures affects plasma testosterone and cortisol
concentrations and furthermore, how these hormones respond to exercise in people suffering spinal cord injuries. The purpose
of this study was to characterize plasma testosterone and cortisol responses to upper body exercise in wheelchair athletes
(WA) compared to able-bodied individuals (AB) at two ambient temperatures. Four WA [mean age 36 (SEM 13) years, mean body
mass 66.9 (SEM 11.8) kg, injury level T7–T11], matched with five AB [mean age 33.4 (SEM 8.9) years, mean body mass 72.5 (SEM 13.1) kg] exercised (cross-over design) for
20 min on a wheelchair ergometer (0.03 kg resistance · kg−1 body mass) at 25 °C and 32 °C. Blood samples were obtained before (PRE), at min 10 (MID), and min 20 (END) of exercise. No
differences were found between results obtained at 25 °C and 32 °C for any physiological variable studied and therefore these
data were combined. Pre-exercise testosterone concentration was lower (P < 0.05) in WA [18.3 (SEM 0.9) nmol · l−1] compared to AB [21.9 (SEM 3.6) nmol · l−1], and increased PRE to END only in WA. Cortisol concentrations were similar between groups before and during exercise, despite
higher rectal temperatures in WA compared to AB, at MID [37.21 (SEM 0.14) and 37.02 (SEM 0.08)°C, respectively] and END
[37.36 (SEM 0.16) and 37.19 (SEM 0.10)°C, respectively]. Plasma norepinephrine responses were similar between groups. In conclusion,
there were no differences in plasma cortisol concentrations, which may have been due to the low relative exercise intensities
employed. The greater exercise response in WA for plasma testosterone should be confirmed on a larger population. It could
have been the result of the lower plasma testosterone concentrations at rest in our group.
Accepted: 4 September 2000 相似文献
7.
Para-chloro-2-[18F]fluoroethyl-etomidate: A promising new PET radiotracer for adrenocortical imaging
Isabella Silins Anders Sundin Patrik Nordeman Mahabuba Jahan Sergio Estrada Azita Monazzam Mark Lubberink Franklin Aigbirhio Per Hellman Gunnar Antoni 《International journal of medical sciences》2021,18(10):2187
Introduction: [11C]Metomidate ([11C]MTO), the methyl ester analogue of etomidate, was developed as a positron emission tomography (PET) radiotracer for adrenocortical tumours and has also been suggested for imaging in primary aldosteronism (PA). A disadvantage of [11C]MTO is the rather high non-specific binding in the liver, which impacts both visualization and quantification of the uptake in the right adrenal gland. Furthermore, the short 20-minute half-life of carbon-11 is a logistic challenge in the clinical setting.Objectives: The aim of this study was to further evaluate the previously published fluorine-18 (T1/2=109.5 min) etomidate analogue, para-chloro-2-[18F]fluoroethyl etomidate; [18F]CETO, as an adrenal PET tracer.Methods: In vitro experiments included autoradiography on human and cynomolgus monkey (non-human primate, NHP) tissues and binding studies on adrenal tissue from NHPs. In vivo studies with [18F]CETO in mice, rats and NHP, using PET and CT/MRI, assessed biodistribution and binding specificity in comparison to [11C]MTO.Results: The binding of [18F]CETO in the normal adrenal cortex, as well as in human adrenocortical adenomas and adrenocortical carcinomas, was shown to be specific, both in vitro (in humans) and in vivo (in rats and NHP) with an in vitro Kd of 0.66 nM. Non-specific uptake of [18F]CETO in NHP liver was found to be low compared to that of [11C]MTO.Conclusions: High specificity of [18F]CETO to the adrenal cortex was demonstrated, with in vivo binding properties qualitatively surpassing those of [11C]MTO. Non-specific binding to the liver was significantly lower than that of [11C]MTO. [18F]CETO is a promising new PET tracer for imaging of adrenocortical disease and should be evaluated further in humans. 相似文献
8.
Deepti Mittal Vinod Kumar Suresh Chandra Saxena Niranjan Khandelwal Naveen Kalra 《Medical & biological engineering & computing》2010,48(12):1281-1291
Speckle is a primary factor which degrades the contrast resolution and masks the meaningful texture information present in
an ultrasound image. Its presence severely hampers the interpretation and analysis of ultrasound images. When speckle reduction
technique is applied for visual enhancement of ultrasound images, it is to be kept in mind that blurring associated with speckle
reduction should be less and fine details are properly enhanced. With these points in consideration, the modified speckle
reduction anisotropic diffusion (MSRAD) method is proposed in the present study to improve the visual quality of the ultrasound
images. In the proposed MSRAD method, the four neighboring pixel template in speckle reduction anisotropic diffusion (SRAD)
method of Yu and Acton (IEEE Trans Image Process 11:1260–1270, 2002) have been replaced by a new template of larger number
of neighboring pixels to calculate the diffusion term. To enhance visual quality of ultrasound images, nonquadratic regularization
(Yu and Yadegar, Proceedings of the IEEE international conference on image processing, 2006) is incorporated with MSRAD method
and accordingly changes in parameter settings have been made. The performance of MSRAD method was evaluated using clinical
ultrasound images, interpretation by the medical experts and results of MSRAD method by subjective and objective criteria. 相似文献
9.
Dr E. Marzec 《Medical & biological engineering & computing》2001,39(5):558-561
The dielectric method has been applied to study the relaxation mechanisms of non-irradiated and γ-irradiated keratin-water
systems in the electric field frequency range of 101–105 Hz and at temperatures from 22 to 190°C. Measurements were performed for keratin samples containing 3% water by mass at room
temperature. The doses of γ-irradiation were 5, 50 and 200 kGy. The influence of water and γ-irradiation on the dielectric
behaviour of keratin was negligible up to 120°C but significant in the temperature range of 140–190°C. In the first temperature
range, the motion of polar side chains was characterised by a low activation energy of 11 kJ mol−1, while longer relaxation times varied from 418 to 155 ms. In the range 140–190°C, the release of the strongly bound water
in keratin samples irradiated with doses of 0–50 kGy was evidenced by the high value of the activation energy of 84 kJ mol−1 and shorter relaxation times varying from 43 to 3 ms. The value of the activation energy decreased to 55 kJ mol−1 for keratin samples irradiated with 200 kGy as a result of degradation of the hydrogen bond between the water and polar groups
of the main chain of the macromolecule. The results presented may be useful in bio-electrical impedance analysis, for physiological
and clinical research. The method applied in vivo should permit detection of changes in the stratum corneum induced by water,
ionising radiation, cosmetics and diseases such as fibromyalagia or diabetic foot ulcers. 相似文献
10.
The detection of pulsatile blood flow velocity through one section of a curved branching frog mesenteric microvessel during
a flow cycle, by analysis of a sequence of videomicroscopic images recorded at a frame rate 25 frames s−1, is presented. From these data, 64 sequential digitised frames of 128×128 pixels and 256 grey level were selected. By processing
sequential pairs of frames by image velocimetry, the corresponding displacement vector was calculated. Dividing this by the
frame rate gave the vector velocity. The same procedure was repeated for all frames, and the corresponding maximum (0.36–0.38
mm s−1), minimum (0.0–0.025 mm s−1) and other velocity values were obtained and plotted. The preliminary data analysis showed that the separation between two
velocity maxima was about 20 video frames, which corresponded to one cardiac cycle of time interval 0.8 s. 相似文献
11.
In blood from the portal vein of anaesthetized rats the levels of histamine and putrescine were 2–3-fold lower compared to
arterial blood. Putrescine concentration was increased severalfold and the difference between portal and arterial blood abolished
in animals pretreated with the specific diamine oxidase inhibitor aminoguanidine. Histamine concentration was 40% lower in
portal compared to arterial blood in animals treated with the mast cell degranulator compound 48/80. In animals pretreated
with aminoguanidine, compound 48/80 enhanced the level of histamine and no difference was observed between arterial and portal
blood. The amounts of intravenously injected [14C]-labeled histamine was about 15% lower in portal compared to arterial blood. The uptake of [14C]-putrescine from the small intestine was estimated. In urine from animals pretreated with aminoguanidine the concentration
of [14C]-putrescine was more than 40-times higher than in control animals corresponding to a calculated uptake of about 7% in aminoguanidine
treated animals. Our results suggest that intestinal diamine oxidase clears the blood from diamines and prevents luminal uptake
of putrescine.
accepted by W. Lorenz 相似文献
12.
Rangaraj M. Rangayyan Thanh M. Nguyen Fábio J. Ayres Asoke K. Nandi 《Journal of digital imaging》2010,23(5):547-553
The effect of pixel resolution on texture features computed using the gray-level co-occurrence matrix (GLCM) was analyzed
in the task of discriminating mammographic breast lesions as benign masses or malignant tumors. Regions in mammograms related
to 111 breast masses, including 65 benign masses and 46 malignant tumors, were analyzed at pixel sizes of 50, 100, 200, 400,
600, 800, and 1,000 μm. Classification experiments using each texture feature individually provided accuracy, in terms of
the area under the receiver operating characteristics curve (AUC), of up to 0.72. Using the Bayesian classifier and the leave-one-out
method, the AUC obtained was in the range 0.73 to 0.75 for the pixel resolutions of 200 to 800 μm, with 14 GLCM-based texture
features using adaptive ribbons of pixels around the boundaries of the masses. Texture features computed using the ribbons
resulted in higher classification accuracy than the same features computed using the corresponding regions within the mass
boundaries. The t test was applied to AUC values obtained using 100 repetitions of random splitting of the texture features from the ribbons
of masses into the training and testing sets. The texture features computed with the pixel size of 200 μm provided the highest
average AUC with statistically highly significant differences as compared to all of the other pixel sizes tested, except 100 μm. 相似文献
13.
We propose a method to do constrained parameter estimation and inference from neuroimaging data using general linear model
(GLM). Constrained approach precludes unrealistic hemodynamic response function (HRF) estimates to appear at the outcome of
the GLM analysis. The permissible ranges of waveform parameters were determined from the study of a repertoire of plausible
waveforms. These parameter intervals played the role of prior distributions in the subsequent Bayesian analysis of the GLM,
and Gibbs sampling was used to derive posterior distributions. The method was applied to artificial null data and near infrared
spectroscopy (NIRS) data. The results show that constraining the GLM eliminates unrealistic HRF waveforms and decreases false
activations, without affecting the inference for “realistic” activations, which satisfy the constraints. 相似文献
14.
J. Fröhlich T. Kullmer A. Urhausen R. Bergmann W. Kindermann 《European journal of applied physiology》1989,59(1-2):98-103
Summary Twenty-four top-level body builders [13 anabolic steroid users (A); 11 non-users (N)] and 11 performance-matched controls
(C) were examined to determine the effect on lipids, lipoproteins and apolipoproteins of many years of body building with
and without simultaneous intake of anabolic steroids and testosterone. After an overnight fast, triglycerides (TG), total
cholesterol (TOTC), high density lipoprotein cholesterol (HDLC), low density lipoprotein cholesterol (LDLC), the HDLC subfractions
HDL2C and HDL3C, as well as apolipoprotein A-I (Apo A-I), apolipoprotein A-II (Apo A-II) and apolipoprotein B (Apo B) were determined. Both
A and N, compared to C, showed significantly lower HDLC and higher LDLC concentrations, with the differences between A and
C clearly pronounced. In a subgroup of 6 body builders taking anabolic steroids at the time of the study, HDLC, HDL2C, HDL3C, Apo A-I and Apo A-II were all significantly lower and LDLC was significantly higher than in a second subgroup of 7 body
builders who had discontinued their intake of anabolic steroids at least 4 weeks prior to the study. In some single cases
HDLC was barely detectable (2–7 mg·dl−1). The TG and TOTC remained unchanged. The present findings suggest that many years of body building among top-level athletes
have no beneficial effect on lipoproteins and apolipoproteins. Simultaneous use of anabolic steroids results in part in extreme
alterations in lipoproteins and apolipoproteins, representing an atherogenic profile. After discontinuing the use of anabolic
steroids, the changes in lipid metabolism appear to be reversible. 相似文献
15.
This study evaluated whether the heart rate (HR) response to exercise depends on body position and on the active muscle mass.
The HR response to ergometer rowing (sitting and using both arms and legs) was compared to treadmill running (upright exercise
involving mainly the legs) using a progressive exercise intensity protocol in 55 healthy men [mean (SD) height 176 (5) cm,
body mass 71 (6) kg, age 21 (3) years]. During rowing HR was lower than during running at a blood lactate concentration of
2 mmol·l–1 [145 (13) compared to 150 (11) beat·min–1, P<0.05], 4 mmol·l–1 [170 (10) compared to 177 (13) beat·min–1, P<0.05], and 6 mmol·l–1 [182 (10) compared to 188 (10) beat·min–1, P<0.05]. Also during maximal intensity rowing, HR was lower than during maximal intensity running [194 (9) compared to 198 (11) beat·min–1, P<0.05]. These results were accompanied by a higher maximal oxygen uptake during rowing than during running [rowing compared
to running, 4.50 (0.5) and 4.35 (0.4) l·min–1, respectively, P<0.01]. Thus, the oxygen pulse, as an index of the stroke volume of the heart, was higher during rowing than during running
at any given intensity. The results suggest that compared to running, the seated position and/or the involvement of more muscles
during rowing facilitate venous return and elicit a smaller HR response for the same relative exercise intensity.
Electronic Publication 相似文献
16.
O. E. Osadchii V. M. Pokrovskii O. G. Kompaniets A. N. Kurzanov 《Bulletin of experimental biology and medicine》1997,124(5):1056-1058
The effects of neurotensin and its analog [d-Trp11]-neurotensin were studied on Wenckebach arrhythmia and atrioventricular dissociation provoked by vagal volley stimulation.
In both cases the antiarrhythmic effect of neurotensin was observed, which was mediated by activation of cardiac β-adrenoreceptors
and manifested 40–60 sec after its administration. The neurotensin analog had no cardioprotective activity, but when applied
before neurotensin, it demonstrated antagonism to the protective effect of natural neurotensin.
Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 11, pp. 495–497, November, 1997 相似文献
17.
Computer simulations were carried out to appraise three new criteria for the estimation of baroreflex sensitivity (BRS) using
the tranfer function method. The major goal was to identify a computation procedure able to overcome the intrinsic limitations
of the classical coherence criterion. Four representative shapes of the gain function and three different average agains (2,
5 and 8 ms(mmHg)−1) in the lowfrequency (LF) band (0.04–0.15 Hz) were considered. The signal-to-noise ratio was made to vary so that the peak
coherence in the LF band changed from 0.15 to 0.9 All simulation parameters were derived from previous observations in healthy
subjects and heart disease patients. The error of the estimated gain function was obtained from its confidence interval. BRS
was computed as average gain in the LF band: (a) including in the average only those points having error≤ threshold (criterion
1, C1); (b) calculating the mean error in the band and accepting BRS measurements only when this error was ≤ threshold (criterion
2, C2); (c) including in the average all points, regardless of the error (criterion 3, C3). The three criteria were compared
in terms of measurability (percentage of measured BRS) and accuracy (bias and SD of BRS). Using C1 and C2, measureability
dropped to 10% when the peak cohrence in the LF band decreased, respectively, to 0.18–0.41 and to 0.26–0.53, depending on
the shape and strength of the gain. In this condition (lower bound of measureability), worst bias and SD (average gain: 8
ms(mmHg)−1) were, respectively, 0.8 ms(mmHg)−1 and 3.3 ms(mmHg)−1 (C1), and 0.1 ms(mmHg)−1 and 1.0 ms(mmHg)−1 (C2), C3, by definition, always ensured 100% measurability and showed bias and SD comparable with, or even lower than, C1
and C2, within the common range of measurable BRS. In the extreme condition of 0.15 coherence, bias and SD were, respectively,
1.7 ms(mmHg)−1 and 2.3 ms(mmHg)−1 (average gain: 8 ms(mmHg)−1). Hence, error checking (C1 and C2) dramatically reduced measurability and did not improve accuracy of BRS measurements compared
with performing no error check (C3). In conditions of low signal-to-noise ratio and/or impaired baroreflex gain, leading to
markedly reduced coherence, the simple average of the gain function in the LF band allows BRS to be estimated with accuracy
adequate for clinical purposes. 相似文献
18.
Miklós Tóth Philip Little Fabian Arnberg Jenny Häggkvist Jan Mulder Christer Halldin Balázs Gulyás Staffan Holmin 《Brain structure & function》2016,221(3):1279-1290
Adequate estimation of neuroinflammatory processes following ischemic stroke is essential for better understanding of disease mechanisms, and for the development of treatment strategies. With the TSPO (18 kDa translocator protein) positron emission tomography (PET) radioligand [11C]PBR28, we monitored longitudinally the inflammatory response post-transient cerebral ischemia in rats, using a recently developed rat stroke model that produces isolated focal cortical infarcts with clinical relevance in size and pathophysiology. Six Sprague–Dawley rats were subjected to 90 min transient endovascular occlusion of the M2 segment of the middle cerebral artery (M2CAO). Animals were imaged with a nanoScan® PET/MRI system at 1, 4, 7 and 14 days after M2CAO with a bolus injection of [11C]PBR28. In the infarct region, we found a significantly increased uptake of [11C]PBR28 on day 4, 7 and 14 compared to day 1 as well as compared to the contralateral cortex. No significant increase was detected in the contralateral cortex during the 14 days of imaging. The activation in the infarct region gradually decreased between day 4 and day 14. In an additional group of animals (n = 26), immunofluorescence studies were performed with antibodies for activated microglia/monocytes (Cd11b), phagocytes (Cd68), astrocytes (glial fibrillary acidic protein) and TSPO. The TSPO immunofluorescence signal indicated reactive microgliosis post injury, corresponding to PET findings. The present clinically relevant animal model and TSPO PET ligand appear to be well suited for studies on neuroinflammation after ischemic stroke. 相似文献
19.
Image registration and motion estimation play central roles in many fields, including RADAR, SONAR, light microscopy, and
medical imaging. Because of its central significance, estimator accuracy, precision, and computational cost are of critical
importance. We have previously presented a highly accurate, spline-based time delay estimator that directly determines sub-sample
time delay estimates from sampled data. The algorithm uses cubic splines to produce a continuous representation of a reference
signal and then computes an analytical matching function between this reference and a delayed signal. The location of the
minima of this function yields estimates of the time delay. In this paper we describe the MUlti-dimensional Spline-based Estimator
(MUSE) that allows accurate and precise estimation of multi-dimensional displacements/strain components from multi-dimensional
data sets. We describe the mathematical formulation for two- and three-dimensional motion/strain estimation and present simulation
results to assess the intrinsic bias and standard deviation of this algorithm and compare it to currently available multi-dimensional
estimators. In 1000 noise-free simulations of ultrasound data we found that 2D MUSE exhibits maximum bias of 2.6 × 10−4 samples in range and 2.2 × 10−3 samples in azimuth (corresponding to 4.8 and 297 nm, respectively). The maximum simulated standard deviation of estimates
in both dimensions was comparable at roughly 2.8 × 10−3 samples (corresponding to 54 nm axially and 378 nm laterally). These results are between two and three orders of magnitude
better than currently used 2D tracking methods. Simulation of performance in 3D yielded similar results to those observed
in 2D. We also present experimental results obtained using 2D MUSE on data acquired by an Ultrasonix Sonix RP imaging system
with an L14-5/38 linear array transducer operating at 6.6 MHz. While our validation of the algorithm was performed using ultrasound
data, MUSE is broadly applicable across imaging applications. 相似文献
20.
The thermoregulatory responses of ten paraplegic (PA; T3/4-L4) and nine able-bodied (AB) upper body trained athletes were
examined at rest and during prolonged arm-cranking exercise and passive recovery. Exercise was performed for 90 min at 80%
peak heart rate, and at 21.5 (1.7)°C and 47.0 (7.8)% relative humidity on a Monark cycle ergometer (Ergomedic 814E) adapted
for arm exercise. Mean peak oxygen uptake values for the PA and AB athlete groups were 2.12 (0.41) min−1 and 3.19 (0.38) l · min−1, respectively (P<0.05). At rest, there was no difference in aural temperature between groups [36.2 (0.4)°C for both groups]. However, upper
body skin temperatures for the PA athletes were approximately 1.0 °C warmer than for the AB athletes, whereas lower body skin
temperatures were cooler than those for the AB athletes (1.3 °C and 2.7 °C for the thigh and calf, respectively). Upper and
lower body skin temperatures for the AB athletes were similar. During exercise, blood lactate peaked after 15 min of exercise
for both groups [3.33 (1.26) mmol · l−1 and 4.30 (1.03) mmol · l−1 for the PA and AB athletes, respectively, P<0.05] and decreased throughout the remainder of the exercise period. Aural temperature increased by 0.7 (0.5)°C and 0.6 (0.4)°C
for the AB and PA athletes, respectively. Calf skin temperature for the PA athletes increased during exercise by 1.4 (2.8)°C
(P<0.05), whereas a decrease of 0.8 (2.0)°C (P<0.05) was observed for the AB athletes. During the first 20 min of recovery from exercise, the calf skin temperature of the
AB athletes decreased further [−2.6 (1.3)°C; P<0.05]. Weight losses and changes in plasma volume were similar for both groups [0.7 (0.5) kg and 0.7 (0.4) kg; 5.4 (4.9)%
and 9.7 (6.2)% for the PA and AB athletes, respectively]. In conclusion, the results of this study suggest that the PA athletes
exhibit different thermoregulatory responses at rest and during exercise and passive recovery to those of upper body trained
AB athletes. Despite this, during 90 min of arm-crank exercise in a cool environment, the PA athletes appeared to be at no
greater thermal risk than the AB athletes.
Accepted: 7 May 1997 相似文献