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PubMedDate not supplied

Endoscopic cellular microscopy for in vivo biomechanical assessment of tendon function.

This study explores a novel method to quantify in vivo soft tissue biomechanics from endoscopic confocal fluorescence microscope images of externally loaded biological tissues. A custom algorithm based on normalized cross-correlation is used to track fluorescently labeled cells within soft tissue structures as they deform. Cellular displacements are subsequently reduced to tissue strains by deriving the spatial gradient of the spline smoothed cellular displacement field. The relative performance of the tracking method is verified using a synthetic dataset with known underlying deformation. In biological application of the method, tissue strains are measured in the Achilles tendon of an anesthetized mouse. Over repeated trials, structural strain in the tendon (i.e., the relative change in distance between cells located at view field extremes) is 20.3+/-3.1%, thus establishing the reproducibility of the loading protocol. Analysis of local tendon tissue strains reveal primary engineering strains in the tissue to range from 5 to 55%, signifying a highly inhomogeneous strain state, with complex relative motions of neighboring tendon substructures. In summary, the current work establishes a baseline for a promising experimental method, and demonstrates its technical feasibility.

Animals↗

PubMed2006

Multiple particle tracking in 3-D+t microscopy: method and application to the tracking of endocytosed quantum dots.

We propose a method to detect and track multiple moving biological spot-like particles showing different kinds of dynamics in image sequences acquired through multidimensional fluorescence microscopy. It enables the extraction and analysis of information such as number, position, speed, movement, and diffusion phases of, e.g., endosomal particles. The method consists of several stages. After a detection stage performed by a three-dimensional (3-D) undecimated wavelet transform, we compute, for each detected spot, several predictions of its future state in the next frame. This is accomplished thanks to an interacting multiple model (IMM) algorithm which includes several models corresponding to different biologically realistic movement types. Tracks are constructed, thereafter, by a data association algorithm based on the maximization of the likelihood of each IMM. The last stage consists of updating the IMM filters in order to compute final estimations for the present image and to improve predictions for the next image. The performances of the method are validated on synthetic image data and used to characterize the 3-D movement of endocytic vesicles containing quantum dots.

Algorithms↗

PubMed1981

Acquisition of depth discrimination in a Japanese macaque: a preliminary study.

A training method of depth discrimination in a Japanese monkey was reported. Using a Howard-Dohlman type apparatus, the monkey was required to discriminate the distance of two rods. Observation distance was 785 mm and a tracking method was employed. Difference thresholds measured preliminarily were 23.6 mm and 77.1 mm for binocular and monocular conditions, respectively.

Animals↗

PubMed1994

An algorithm for automatic tracking of nuclear boundaries.

An image segmentation algorithm, based on boundary tracking, was introduced to achieve automatic segmentation of nuclei. This will improve reliability and reproducibility for the computer-assisted grading of routinely stained material, especially from biopsies, which often offer only scanty clinical material. Nuclear grading systems using karyometric features were developed earlier. However, hematoxylin and eosin-stained tissues have proven difficult for automatic segmentation, which is a crucial part of an objective grading system. In this paper we describe an automatic tracking method that traces nuclear boundaries on the basis of edge information and local boundary features. There were two phases to the procedure. First, approximate boundaries were extracted by automatic thresholding; then, boundaries were refined through interactive tracking. The results are encouraging.

Algorithms↗

PubMed1991

The design of CAST (Computer-Aided Speechreading Training).

The underlying theoretical assumptions, goals, design, and implementation of a Computer-Aided Speechreading Training system (CAST) are described as a case study in program design. This computerized speechreading assessment and training system simulates face-to-face intervention and is designed to be one component of a comprehensive aural rehabilitation program for preretirement adults with acquired mild-to-moderate hearing loss. The interactive, automated course consists of eight training lessons, each focusing on a particular viseme that is practiced by a modified discourse tracking method using viseme-specific texts. Three basic speechreading skills are emphasized: visual speech perception, use of linguistic redundancy, and use of feedback between message sender and receiver. These skills are evaluated separately by means of CAST tracking rate, receiver strategy, and inferred error type. Four example case assessments are provided to illustrate the potential applications of CAST as a standardizable rehabilitative tool. An independent program evaluation is provided in a companion paper (Gagné, Dinon, & Parsons, 1991). Comparisons between CAST, face-to-face tracking procedures, and natural discourse are presented and discussed with reference to theoretical and clinical issues in speechreading and program evaluation.

Computer-Assisted Instruction↗

PubMed2005

Quantum dots to monitor RNAi delivery and improve gene silencing.

A critical issue in using RNA interference for identifying genotype/phenotype correlations is the uniformity of gene silencing within a cell population. Variations in transfection efficiency, delivery-induced cytotoxicity and 'off target' effects at high siRNA concentrations can confound the interpretation of functional studies. To address this problem, we have developed a novel method of monitoring siRNA delivery that combines unmodified siRNA with seminconductor quantum dots (QDs) as multi color biological probes. We co-transfected siRNA with QDs using standard transfection techniques, thereby leveraging the photostable fluorescent nanoparticles to track delivery of nucleic acid, sort cells by degree of transfection and purify homogenously-silenced subpopulations. Compared to alternative RNAi tracking methods (co-delivery of reporter plasmids and end-labeling the siRNA), QDs exhibit superior photostability and tunable optical properties for an extensive selection of non-overlapping colors. Thus this simple, modular system can be extended toward multiplexed gene knockdown studies, as demonstrated in a two color proof-of-principle study with two biological targets. When the method was applied to investigate the functional role of T-cadherin (T-cad) in cell-cell communication, a subpopulation of highly silenced cells obtained by QD labeling was required to observe significant downstream effects of gene knockdown.

Animals↗

PubMed1989

Abnormal optokinetic and perceptual span parameters in cerebellar-vestibular dysfunction and related anxiety disorders.

As prior studies indicated abnormal cerebellar-vestibular-based sensorimotor mechanisms and neurological and ENG diagnostic parameters in anxiety disorders and because ocular fixation and sequential scanning are cerebellar-vestibular-modulated, it appeared reasonable to measure these and related ocular functions in matched samples of anxiety-disordered and control subjects. In this study, the optokinetically-determined fixation, sequential scanning, and perceptual span capacities obtained by means of a newly revised blurring-speed method were significantly lower or impaired in 70 anxiety-disordered patients vs 70 controls. Such data supported further the hypothesis that there may be cerebellar-vestibular predispositions to anxiety disorders and the optokinetically-based tracking method may prove useful in separating a diverse array of CV-determined or related anxiety symptoms from those of other origins. However, independent validation as well as additional studies of anxiety disorders using larger samples vs random or "normal" controls are required before conclusions are justified.

Adolescent↗

PubMed2005

Lattice Boltzmann interface capturing method for incompressible flows.

A lattice Boltzmann interface capturing method for incompressible flows is proposed in this paper. The interface is naturally captured by minimizing the free energy functional. It is easily implemented and does not require interface reconstruction as required by most of the traditional interface tracking methods such as the volume of fluid method. Moreover, the method does not require the isotropic property of the fourth order lattice tensor as do other lattice Boltzmann methods. Thus the D2Q5 (D2 means two dimensional, Q5 means five velocity model) discrete velocity model is applied in the method. The interface profile along the flat interface and coexistence curve can be given analytically. The proposed method is validated for some test cases, and compared to the volume of fluid and level set methods. Numerical results show that the present method performs very well and can generate very sharp interfaces.

Journal Article↗

PubMedDate not supplied

Clinician compliance with primary prevention of tobacco use: the impact of social contingencies.

BACKGROUND: This study evaluated clinicians' compliance with delivering written advice and information against tobacco use (prevention prescriptions) to adolescent patients. METHODS: Clinicians in 77 orthodontic offices were trained (and asked) to provide anti-tobacco counseling and prescriptions to 10- to 18-year-olds for 2 years. Each of eight prescriptions was provided for distribution to adolescent patients. Information concerning prescription-tracking methods and operant learning theory variables such as modeling and feedback was obtained using a cross-sectional interview of clinical staff. The proportion of prescriptions written was regressed on possible "determinants." Analyses were replicated for two time periods. RESULTS: Mean anti-tobacco prescription compliance was 66 and 73% for two separate time periods. Multiple regression analyses were computed for the first (R = 0.45, F(7,63) = 2.29, P < 0.001) and second (R = 0.48, F(7,63) = 2.76, P < 0.001) time periods. Prescription tracking and praise from patients were significant correlates for the first time period; praise and modeling were significant for the second time period. Twenty and twenty-three percent, respectively, of the variance in office prescription rate was explained. CONCLUSIONS: Results suggest that compliance with primary prevention procedures may be influenced by feedback from patients, staff modeling, and formal office tracking information.

Adolescent↗

PubMed2004

Registering the response of tissues exposed to an interferential electric current stimulation.

Electrotherapy is a treatment method in which an electric stimulus is used to achieve physiological changes in the body. When increasing the level of the electric stimulus, three sensory, three motor and a pain response can be found. In this paper the three sensory threshold levels (1st just noticeable weak tingling sensation, 2nd a very fine but definite tingling and 3rd moderate strong tingling) were studied with an interferential electric current stimulus. The interferential electric current can be achieved by summing two alternating currents with little different frequencies with each other. As a current source, the study used a value intended for interferential electric current therapy. The threshold value measurements were performed on 5 days to 6 volunteers. The method of limits is a frequently used technique for determining sensory thresholds where ascending or descending stimuli is used and the observer reports of the appearance or disappearance of the sensation, respectively. A Bekesy's algorithm is a threshold tracking method with a variable stimulus. They were used for controlling the interferential electric current stimulus, and hence, for studying the,thresholds. By using the method of limits, the measurements were done at three sensory threshold levels at interferential frequencies deltaf of 10 Hz, 30 Hz, 50 Hz, and 100 Hz caused by two sine waves, one with a frequency between 2490 Hz and 2400 Hz, and the other constant 2500 Hz. In the method based on Bekésy's algorithm the interferential frequency deltaf was increased from 1 Hz to 100 Hz by changing the first frequency from 2499 Hz to 2400 Hz and the measurement was repeated for all three sensory thresholds. The sensory thresholds for interferential current stimuli seem to be quite unaffected by the interferential electric current frequency among the healthy test persons, and no distinct interferential electric current frequencies at which the threshold values should be measured were found in this study.

Adult↗

PubMed2002

Automated 3-D echocardiography analysis compared with manual delineations and SPECT MUGA.

A major barrier for using 3-D echocardiography for quantitative analysis of heart function in routine clinical practice is the absence of accurate and robust segmentation and tracking methods necessary to make the analysis automatic. In this paper, we present an automated three-dimensional (3-D) echocardiographic acquisition and image-processing methodology for assessment of left ventricular (LV) function. We combine global image information provided by a novel multiscale fuzzy-clustering segmentation algorithm, with local boundaries obtained with phase-based acoustic feature detection. We then use the segmentation results to fit and track the LV endocardial surface using a 3-D continuous transformation. To our knowledge, this is the first report of a completely automated method. The protocol is evaluated in a small clinical case study (nine patients). We compare ejection fractions (EFs) computed with the new approach to those obtained using the standard clinical technique, single-photon emission computed tomography multigated acquisition. Errors on six datasets were found to be within six percentage points. A further two, with poor image quality, improved upon EFs from manually delineated contours, and the last failed due to artifacts in the data. Volume-time curves were derived and the results compared to those from manual segmentation. Improvement over an earlier published version of the method is noted.

Algorithms↗

PubMed2005

A finite-element method model of soft tissue response to impulsive acoustic radiation force.

Several groups are studying acoustic radiation force and its ability to image the mechanical properties of tissue. Acoustic radiation force impulse (ARFI) imaging is one modality using standard diagnostic ultrasound scanners to generate localized, impulsive, acoustic radiation forces in tissue. The dynamic response of tissue is measured via conventional ultrasonic speckle-tracking methods and provides information about the mechanical properties of tissue. A finite-element method (FEM) model has been developed that simulates the dynamic response of tissues, with and without spherical inclusions, to an impulsive acoustic radiation force excitation from a linear array transducer. These FEM models were validated with calibrated phantoms. Shear wave speed, and therefore elasticity, dictates tissue relaxation following ARFI excitation, but Poisson's ratio and density do not significantly alter tissue relaxation rates. Increased acoustic attenuation in tissue increases the relative amount of tissue displacement in the near field compared with the focal depth, but relaxation rates are not altered. Applications of this model include improving image quality, and distilling material and structural information from tissue's dynamic response to ARFI excitation. Future work on these models includes incorporation of viscous material properties and modeling the ultrasonic tracking of displaced scatterers.

Acoustics↗

PubMed2005

A semiautomated technique for evaluation of uterine peristalsis.

PURPOSE: To evaluate the capability of a newly developed semiautomatic analysis technique for evaluation of uterine peristalsis in comparison with visual assessment. MATERIALS AND METHODS: Cine magnetic resonance (MR) images were obtained from 16 normal volunteers in periovulatory phase. Sixty-eight studies were evaluated by both visual evaluation and by a semiautomated computer assisted software. The software was developed by applying an automated contour tracking method and enables objective analysis of frequency, amplitude, velocity, and direction. Assessments were based on: 1) the recognition of peristalsis, 2) peristaltic direction and frequency, and 3) the way of recognizing peristaltic direction. The data obtained by both modalities were compared with those of previously reported ultrasound (US) findings. RESULTS: Uterine peristalsis was identified in all studies by both objective and visual analyses. There was no significant difference in the identification of peristalsis, recognition of peristaltic directions, or peristaltic frequency (P > 0.05). Data were well in accordance with those in US literature. Peristaltic direction was recognized either by configuration change in the endometrium or by conduction of low signal intensity in the subendometrial myometrium and there was statistically no difference. CONCLUSION: Evaluation of uterine peristalsis by the semiautomatic analysis accorded well with the results obtained visual assessments and previous US findings.

Adult↗

PubMed2002

Quantifying signaling-induced reorientation of T cell receptors during immunological synapse formation.

Productive T cell recognition of antigen-presenting cells (APCs) is normally accompanied by the formation of a cell-cell contact called the "immunological synapse." Our understanding of the steps leading up to this formation has been limited by the absence of tools for analyzing 3D surfaces and surface distributions as they change over time. Here we use a 3D fluorescence quantitation method to show that T cell receptors are recruited in bulk within the first minute after the onset of activation and with velocities ranging from 0.04 to 0.1 microm/s; a speed significantly greater than unrestricted diffusion. Our method reveals a second feature of this reorientation: a conformational change as the T cell pushes more total membrane into the interface creating a larger contact area for additional receptors. Analysis of individual T cell receptor velocities using a single-particle tracking method confirms our velocity measurement. This method should permit the quantitation of other dynamic membrane events and the associated movement of cell-surface molecules.

Animals↗

PubMed2006

Can measurement of the intima-media thickness of the carotid artery improve the diagnostic value of exercise stress tests?

OBJECTIVE: The diagnostic value of the exercise electrocardiogram (ECG) for the detection of coronary artery disease is hampered by a high proportion of equivocal results, especially in asymptomatic patients. The intima-media thickness of the carotid artery correlates well with the degree of atherosclerosis, also in other vascular beds, such as the coronary arteries. The aim of this study is to evaluate whether measurements of intima-media thickness can improve the diagnostic value of stress ECG in the detection of coronary artery disease. METHODS: Patients without a history of vascular disease and with equivocal exercise stress ECG results were included. The intima-media thickness was measured with high resolution echography at the posterior wall of the common carotid artery, using an automated edge-tracking method. The diagnosis of coronary artery disease was based on the presence of reversible perfusion defects on exercise MIBI-scintigrams. RESULTS: A total of 90 patients (46 men, 44 women) with a mean age of 53.7 years were included. The MIBI-scintigraphy was positive in 17. There was no difference in mean intima-media thickness between MIBI positive and MIBI negative patients (635.76 +/- 84.56 microm and 643.89 +/- 107.06 microm, respectively, p = 0.8). Using multiple regression analysis, neither intima-media thickness measurements, nor classic risk factors could predict the result of MIBI-scintigraphy. Intima-media thickness was mainly influenced by age and hypertension. CONCLUSIONS: In this study, neither intima-media thickness measurements, nor classic risk factors could improve the diagnostic value of stress ECG in the detection of coronary artery disease. In case of equivocal stress results, additional cardiovascular imaging techniques remain recommended.

Adult↗

PubMedDate not supplied

Automated local maximum-intensity projection with three-dimensional vessel tracking.

Despite the simplicity and widespread acceptance of the maximum-intensity-projection (MIP) technique for displaying three-dimensional (3D) magnetic resonance angiographic data, several disadvantages are associated with MIP as it is applied to all of the 3D data. These include elevated noise level, reduced contrast between small vessels and background tissue, and the inability to distinguish arteries from veins. The authors have developed a 3D vessel tracking method combined with a local MIP around a given vessel to complement conventional MIP and alleviate these problems. The method is referred to as a traveling MIP (TMIP). TMIP was evaluated in both patients and healthy volunteers. The results indicate that TMIP provides better contrast between vessels and background tissue, better lumen definition, and better vascular visualization than either MIP or vessel tracking alone.

Algorithms↗

PubMed2001

Homotypic cell-cell contacts stimulate the motile activity of rat prostate cancer cells.

OBJECTIVE: To characterize the effect of homotypic cell-to-cell collisions upon the motile activities of two rat prostatic cancer cell lines of markedly different metastatic potential. MATERIALS AND METHODS: The movements of strongly and weakly metastatic MAT-LyLu and AT-2 cells, respectively, were recorded under an inverted microscope at 37 degrees C. The motile activities of the cells at various cell densities were characterized quantitatively by computer-aided tracking methods and image analysis. The following variables were assessed: speed of movement, final displacement, coefficient of movement efficiency, diffusion constant and positive flow. RESULTS: MAT-LyLu and AT-2 cells showed only limited motile activity in sparse cultures where there was little contact amongst the cells. However, under these and all other subsequent conditions tested, the motile activity of the MAT-LyLu cells was higher than the AT-2 cells. As the density of the cultured cells was increased (leading to more cell-to-cell contacts) there was a significant increase in motility. This effect was more pronounced for the AT-2 than for the MAT-LyLu cells, resulting in visible acceleration of movement by direct physical contact among the colliding cells. The motile activities of the tumour cells was only slightly affected by conditioned media. CONCLUSION: Homotypic collisions between migrating prostatic cancer cells can strongly stimulate their motility. The effect of increased contact is greater on the weakly metastatic cells, such that at high cell density, the difference in the motilities of weak and strong metastatic cells is greatly reduced.

Animals↗

PubMed2004

Mechanical properties of Xenopus egg cytoplasmic extracts.

Cytoplasmic extracts prepared from Xenopus laevis eggs are used for the reconstitution of a wide range of processes in cell biology, and offer a unique environment in which to investigate the role of cytoplasmic mechanics without the complication of preorganized cellular structures. As a step toward understanding the mechanical properties of this system, we have characterized the rheology of crude interphase extracts. At macroscopic length scales, the extract forms a soft viscoelastic solid. Using a conventional mechanical rheometer, we measure the elastic modulus to be in the range of 2-10 Pa, and loss modulus in the range of 0.5-5 Pa. Using pharmacological and immunological disruption methods, we establish that actin filaments and microtubules cooperate to give mechanical strength, whereas the intermediate filament cytokeratin does not contribute to viscoelasticity. At microscopic length scales smaller than the average network mesh size, the response is predominantly viscous. We use multiple particle tracking methods to measure the thermal fluctuations of 1 microm embedded tracer particles, and measure the viscosity to be approximately 20 mPa-s. We explore the impact of rheology on actin-dependent cytoplasmic contraction, and find that although microtubules modulate contractile forces in vitro, their interactions are not purely mechanical.

Actins↗