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Results for “tracking methods”

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At least 595 records · Page 33Linked to original sources

PubMed2003

Dynamic tracking of human hematopoietic stem cell engraftment using in vivo bioluminescence imaging.

The standard approach to assess hematopoietic stem cell (HSC) engraftment in experimental bone marrow transplantation models relies on detection of donor hematopoietic cells in host bone marrow following death; this approach provides data from only a single time point after transplantation for each animal. In vivo bioluminescence imaging was therefore explored as a method to gain a dynamic, longitudinal profile of human HSC engraftment in a living xenogeneic model. Luciferase expression using a lentiviral vector allowed detection of distinctly different patterns of engraftment kinetics from human CD34+ and CD34+CD38- populations in the marrow NOD/SCID/beta 2mnull mice. Imaging showed an early peak (day 13) of engraftment from CD34+ cells followed by a rapid decline in signal. Engraftment from the more primitive CD34+CD38- population was relatively delayed but by day 36 increased to significantly higher levels than those from CD34+ cells (P <.05). Signal intensity from CD34+CD38-engrafted mice continued to increase during more than 100 days of analysis. Flow cytometry analysis of bone marrow from mice after death demonstrated that levels of 1% donor cell engraftment could be readily detected by bioluminescence imaging; higher engraftment levels corresponded to higher image signal intensity. In vivo bioluminescence imaging provides a novel method to track the dynamics of engraftment of human HSC and progenitors in vivo.

Animals↗

PubMed2006

Bootstrapped ultrasound calibration.

This paper introduces an enhanced (bootstrapped) method for tracked ultrasound probe calibration. Prior to calibration, a position sensor is used to track an ultrasound probe in 3D space, while the US image is used to determine calibration target locations within the image. From this information, an estimate of the transformation matrix of the scan plane with respect to the position sensor is computed. While all prior calibration methods terminate at this phase, we use this initial calibration estimate to bootstrap an additional optimization of the transformation matrix on independent data to yield the minimum reconstruction error on calibration targets. The bootstrapped workflow makes use of a closed-form calibration solver and associated sensitivity analysis, allowing for rapid and robust convergence to an optimal calibration matrix. Bootstrapping demonstrates superior reconstruction accuracy.

Calibration↗

PubMed2006

Labelling of human mesenchymal stem cells with indium-111 for SPECT imaging: effect on cell proliferation and differentiation.

PURPOSE: Stem cell therapy seems to be a new treatment option within cardiac diseases to improve myocardial perfusion and function. However, the delivery and traceability of the cells represent a problem. Radioactive labelling with 111In could be a method for tracking mesenchymal stem cells (MSCs). However, 111In could influence the viability and differentiation capacity of MSCs, which would limit its use. Therefore, the aim of this study was to evaluate the influence of 111In labelling in doses relevant for SPECT imaging in humans on the viability and differentiation capacity of human MSCs. METHODS AND RESULTS: Human MSCs isolated from bone marrow were incubated with 111In-tropolone (15-800 Bq/cell). The labelling efficiency was approximately 25% with 30 Bq/cell 111In. The MSC doubling time was 1.04+/-0.1 days and was not influenced by 111In within the range 15-260 Bq/cell. Using 30 Bq 111In/cell it was possible to label MSCs to a level relevant for clinical scintigraphic use. With this dose, 111In had no effect on characteristic surface and intracellular markers of cultured MSCs analysed both by flow cytometry and by real-time polymerase chain reaction. Further, the labelled MSCs differentiated towards endothelial cells and formed vascular structures. CONCLUSION: It is possible to label human MSCs with 111In for scintigraphic tracking of stem cells delivered to the heart in clinical trials without affecting the viability and differentiation capacity of the MSCs. This creates an important tool for the control of stem cell delivery and dose response in clinical cardiovascular trials.

Cell Differentiation↗

PubMed2005

Long-term evaluation of motor function following intraneural injection of ropivacaine using walking track analysis in rats.

BACKGROUND: There is a paucity of data regarding neurologic function following nerve injury. Our objective was the long-term evaluation of motor function following intraneural injection of ropivacaine in rats using the sciatic function index (SFI), derived from walking track analysis. METHODS: Rats were randomly assigned to one of four groups of 13 animals each. A needle was inserted under magnification into the left sciatic nerve and 0.2 ml of normal saline, formalin 15%, ropivacaine 0.2 or 0.75% were injected intraneurally. The right side was sham operated. Walking track analysis was performed the day before and on days 1, 4, 7, 11, 15, 18, 21, and 67 following intraneural injection. At the end of the experiment (day 67) a semi-quantitative evaluation of neuropathologic changes was performed by three independent observers. RESULTS: Animals treated with saline and ropivacaine (0.2 and 0.75%) had no detectable impairment of motor function at any time point. In contrast, rats treated with formalin had a complete loss of motor function immediately after the intraneural injection, which persisted until day 21 and returned to normal by day 67. Important histopathologic changes (score=2) with excellent inter-observer agreement were seen only in the group treated with formalin. This applied to both axonal degeneration and Schwann cell density evaluations. CONCLUSIONS: These findings suggest that intraneural injections of ropivacaine at concentrations routinely used in clinical practice appear to have no deleterious effect on sciatic nerve motor function in this experimental rat model.

Amides↗

PubMed2005

Tracing problem solving in real time: fMRI analysis of the subject-paced Tower of Hanoi.

Previous research has found three brain regions for tracking components of the ACT-R cognitive architecture: a posterior parietal region that tracks changes in problem representation, a prefrontal region that tracks retrieval of task-relevant information, and a motor region that tracks the programming of manual responses. This prior research has used relatively simple tasks to incorporate a slow event-related procedure, allowing the blood oxygen level-dependent (BOLD) response to go back to baseline after each trial. The research described here attempts to extend these methods to tracking problem solving in a complex task, the Tower of Hanoi, which involves many complex steps of cognition and motor actions in rapid succession. By tracking the activation patterns in these regions, it is possible to predict with intermediate accuracy when participants are planning a future sequence of moves. The article describes a cognitive model in the ACT-R architecture that is capable of explaining both the latency data in move generation and the BOLD responses in these three regions.

Adolescent↗

PubMedDate not supplied

High-LET pion dose contours under the LAMPF biomedical channel by plastic track detector scanning.

Cellulose-nitrate plastic track detectors have been tested as high spatial-resolution dosimeters at the Biomedical Channel of the Clinton P. Anderson Meson Physics Facility (LAMPF) at the Los Alamos Scientific Laboratory during pilot clinical trials with negative pi mesons (pions). Six plots of dose contours are presented. Reliable macrodosimetry with track detectors would in principle require detector calibration for the particular conditions of geometry and beam parameters in every case but it is interesting that absolute dose values, estimated from data taken with a quite different calibration geometry, were within 20% of agreement with dose values obtained by electronic dosimetry methods. The track detectors measure only the high linear energy transfer (LET) components produced by the pion beam; it is these components which are of special interest in the negative-pion therapy program. Plastic track detectors appear to have many favorable properties for pion dosimetry.

Elementary Particles↗

PubMed2004

Comparison of contrast-enhanced with non-contrast endosonography in the diagnostics of anal fistulas.

The objective of this paper is to compare the accuracy of standard, non-contrast endosonography (EAS) with contrast-enhanced endosonography (CE-EAS) in the diagnosis of anal fistulas. The group consisted of 126 patients (mean age: 43.1 years) with the clinical diagnosis of anal fistula. For anal endosonography, a Bruel & Kjaer unit with a 7.0-MHz transducer was used with a 3% solution of hydrogen peroxide as the contrast agent (1, 2, 3). In each case, EAS and CE-EAS diagnoses of the type and complexity of anal fistula, as well as the location of the internal opening, were determined. Results showed that CE-EAS was significantly more accurate in diagnosing the type of anal fistulas than NC-EAS (97 vs. 94%, respectively; P=02275), and in differentiating simple from complex tracks (92 vs. 75%, respectively; P<0.00001). CE-EAS was much more accurate in patients with recurrent fistulas (57 vs. 92%, respectively; P<0.00006), whereas in a subgroup of primary tracks, both methods were of comparable accuracy. Sensitivities of CE-EAS and EAS for internal opening were 89 and 65%, respectively. The conclusion of this paper is that CE-EAS significantly increases the accuracy of standard non-contrast EAS and is especially beneficial for the differentiation between simple and complex tracks.

Adolescent↗

PubMed2001

Clustering of cardiovascular risk factors in type 2 diabetes mellitus: prognostic significance and tracking.

AIM: Little attention has been paid to the prognostic significance and tracking effect of risk factor clusters characteristic of type 2 diabetes mellitus. We studied the clustering of eight cardiovascular risk factors (smoking, high body mass index, elevated systolic blood pressure, high serum, low density lipoprotein (LDL) cholesterol, high serum LDL triglycerides, low serum, high density lipoprotein (HDL) cholesterol, high fasting blood glucose and high plasma insulin concentration) and their effect on the prognosis and the tracking effect. METHODS: This study is a population-based prospective follow-up of newly diagnosed type 2 diabetic subjects (n = 133, aged 45-64 years) in Eastern Finland. The following end points were used: all-cause mortality, cardiovascular mortality, and incidences of first myocardial infarction and first stroke. Furthermore, we studied the 'tracking effect' of the risk factor clusters during the 10-year follow-up period. RESULTS: When the clustering of risk factors typical of type 2 diabetes mellitus was taken into account, all-cause mortality increased from 28.6% to 50.0% (p < 0.05) and cardiovascular disease mortality increased from 14.3% to 50.0% (p < 0.01) depending on the number of risk factors present. The incidence of first myocardial infarction increased from 0% to 40.0% (p < 0.05) as the number of risk factors increased from 0 to 5. In survivors, the proportion of individuals with no risk factors decreased and the proportion on individuals with three to four risk factors increased during the 10-year follow-up period despite the high mortality among the group with many risk factors. CONCLUSIONS: The risk factor clusters among type 2 diabetic subjects are of great predictive value and when not aggressively treated, show a relentless increase despite selective mortality.

Blood Glucose↗

PubMed2003

Using self-report and adverse event measures to track health's impact on productivity in known groups.

The use of survey data to measure and monitor health and productivity differences between groups is an issue of increasing importance. This article examines the capacity of productivity self-reports (derived from surveys) and adverse event measures (derived from administrative sources) to differentiate groups with a priori known characteristics. A replication strategy is used to test the contributions that productivity self-reports make, alone as well as above and beyond measures of adverse events, to the discrimination of 5 pairs of groups classified by clinical, job type, and demographic criteria. These tests are conducted on representative samples of the active, largely blue-collar employee population at International Truck and Engine Corporation. The results show that both productivity self-reports and adverse event measures differentiate and track known groups. Even in the presence of highly significant effects from adverse event measures, self-reports improve the assessment of productivity. We conclude that: 1) although the joint use of self-reports and adverse event measures is the better approach, practitioners can use self-reports with the expectation that this method will track group differences in health and productivity when adverse event measures are not available; and 2) survey self-reports make unique and independent contributions when adverse events measures are used.

Absenteeism↗

PubMed2002

Tracking transplanted stem cell migration using bifunctional, contrast agent-enhanced, magnetic resonance imaging.

The ability to track stem cell transplants in the brain by in vivo neuroimaging will undoubtedly aid our understanding of how these cells mediate functional recovery after neural transplantation. One major challenge for the development and refinement of stem cell transplantation is to map the spatial distribution and rate of migration in situ. Here we report a method for tracking transplanted stem cells in the ischemia-damaged rat hippocampus by magnetic resonance imaging (MRI). Before transplantation, stem cells were labeled in vitro either with a novel bifunctional contrast agent, gadolinium rhodamine dextran (GRID), identifiable by both MRI and fluorescence microscopy, or with PKH26, visible exclusively under fluorescence microscopy. At different time points following engraftment, the brains were evaluated by both histology and ex vivo MR imaging. Transplanted stem cells were identified by MRI only if prelabeled with GRID, whereas fluorescence microscopy detected transplanted cells using either label. The distribution of GRID-labeled stem cells identified by MRI corresponded to those detected using fluorescence microscopy. These results demonstrate that GRID-enhanced MRI can reliably identify transplanted stem cells and their migration in the brain.

Animals↗

PubMed2000

Angiogenesis monitored by perfusion with a space-filling microbead suspension.

Numerous laboratories are focusing efforts on delivering gene products to induce or prevent the development of new blood vessels in adults, with the hope of rescuing ischemic tissues, circumventing cardiac bypass surgery, or inhibiting tumor growth. Current approaches to the assessment of vascular continuity involve the introduction of either dyes or fluorescent microspheres to track blood flow. However, dyes and dextrans are subject to leakage when vessels are hyperpermeable, a situation that may occur in studies of tumor vasculature and during efforts to stimulate therapeutic angiogenesis. Furthermore, the microspheres that are used for flow studies do not allow a comprehensive visual analysis of vascular continuity. Here we report a method for the visual assessment of microvascular continuity in mouse muscle under circumstances in which vessels are leaky. The approach involves perfusion of the vasculature with fluorescent beads that are much smaller than those used for flow studies. The suspension behaves like a fluid and completely fills the vessels, yet the beads do not leak from VEGF-permeablized capillaries and remain localized in histological sections. Use of beads with the proper fluorescence emission wavelengths allows immunofluorescent colocalization with vessel-specific markers. We compare this improved method with other methods for tracking vascular continuity involving dextrans and larger beads. This approach should aid in the dynamic study of tumor angiogenesis and the evaluation of efforts to deliver angiogenic factors.

Animals↗

PubMed1995

Feasibility and accuracy of a postcard diary system for tracking healthcare utilization of community-dwelling older persons.

OBJECTIVE: To test the feasibility of and to validate a self-report weekly postcard diary of health care utilization. DESIGN: Case-series and validation study. SETTING: Community-based sample of fee-for-service and health maintenance organization (HMO) patients. PARTICIPANTS: A convenience sample of 24 community-dwelling older persons who had failed a self-administered screen and were eligible for a study of outpatient comprehensive geriatric assessment consultation. MEASUREMENTS: Subjects completed and mailed in a weekly postcard diary documenting medical, counseling, or rehabilitation therapy visits. If a subject did not respond within 10 days after the end of the week, a telephone call was placed to gather the information. For a subset of 10 subjects who were HMO enrollees, all records were reviewed to determine accuracy of the postcard diaries. RESULTS: Of the 24 subjects enrolled, one HMO enrollee dropped out following hip surgery after 4 weeks of completing diaries. The remaining 23 subjects (96% of total entered) provided complete information for 12 weeks. Telephone follow-up to either obtain or clarify utilization information was required for 22% of subjects. For the subset of 10 HMO subjects, seven underreporting, two overreporting, and one incorrect day errors were detected-a total of 10 errors representing 9% of diaries and 1.3% of patient-days. Kappa as a measure of agreement between the two methods (self-report and chart review) was 0.82 (P < .0001). Compared with chart review, the diary report was 75.0% sensitive and 99.8% specific. Positive and negative predictive values were 91.3% and 99.2%, respectively. CONCLUSION: These findings suggest that a postcard diary system with telephone follow-up is both a feasible and reasonably accurate method of tracking health care utilization by community-dwelling older persons, although a small percentage will be unable to adhere to this method.

Aged↗

PubMed1989

A new calculational method to assess the therapeutic potential of Auger electron emission.

This paper discusses a new computer code to estimate the efficacy of Auger electron sources in cancer therapy. Auger electron emission accompanies the decay of many radionuclides already commonly used in nuclear medicine, for example; 99mTc and 201Tl. The range of these electrons is in general sub-cellular, therefore, the toxicity of the source depends on the site of decay relative to the genetic material of the cell. Electron track structure methods have been used which enable the study of energy deposition from Auger sources down to the Angstrom level. A figure for the minimum energy required per single strand break is obtained by fitting our energy deposition calculations for 125I decays in a model of the DNA to experimental data on break lengths from 125I labeled plasmid fragments. This method is used to investigate the efficiency of double strand break production by other Auger sources which have potential value for therapy. The high RBE of Auger sources depends critically on the distance between the source and target material. The application of Auger emitters for therapy may necessitate a carrier molecule that can append the source to the DNA. Many DNA localizing agents are known in the field of chemotherapy, some of which could be carrier molecules for Auger sources; the halogenated thymidine precursors are under scrutiny in this field. The activation of Auger cascades in situ by high energy, collimated X ray and neutron beams is also assessed.

DNA, Neoplasm↗

PubMed2005

An information fusion framework for robust shape tracking.

Abstract-Existing methods for incorporating subspace model constraints in shape tracking use only partial information from the measurements and model distribution. We propose a unified framework for robust shape tracking, optimally fusing heteroscedastic uncertainties or noise from measurement, system dynamics, and a subspace model. The resulting nonorthogonal subspace projection and fusion are natural extensions of the traditional model constraint using orthogonal projection. We present two motion measurement algorithms and introduce alternative solutions for measurement uncertainty estimation. We build shape models offline from training data and exploit information from the ground truth initialization online through a strong model adaptation. Our framework is applied for tracking in echocardiograms where the motion estimation errors are heteroscedastic in nature, each heart has a distinct shape, and the relative motions of epicardial and endocardial borders reveal crucial diagnostic features. The proposed method significantly outperforms the existing shape-space-constrained tracking algorithm. Due to the complete treatment of heteroscedastic uncertainties, the strong model adaptation, and the coupled tracking of double-contours, robust performance is observed even on the most challenging cases.

Algorithms↗

PubMed2004

Tracking regression and progression of atherosclerosis in human carotid arteries using high-resolution magnetic resonance imaging.

BACKGROUND AND PURPOSE: Magnetic resonance imaging (MRI) can accurately and reproducibly measure the volume of atherosclerotic plaque in human carotid arteries. Atherosclerotic plaques may either progress or regress over time, depending on individual risk factors and treatment regimens. This study was designed to determine if regression or progression of human carotid atherosclerosis in patients receiving statin therapy over 24 months can be detected by high-resolution MRI. METHODS: In 11 subjects who had undergone unilateral carotid endarterectomy and were on statin therapy, volumes for total carotid artery, concentric wall (normal wall), eccentric wall (plaque), and lumen were quantified at 0, 16 and 24 months using a 1.5-T human imager equipped with 6-cm phased array coils. RESULTS: The interobserver mean coefficient of variation (CV) was lowest for the lumen volume (3.1%) and highest for the plaque volume (9.8%). The interscan mean CV was lowest for the total artery volume (3.2%) and highest for the plaque volume (9.9%). As much as 26% regression and 35% progression were observed in individual subject's carotid artery eccentric wall (plaque) volumes over time. Mean eccentric wall volume increased 5% by 16 months and 8% by 24 months. Mean total wall volume increased slightly at both 16 and 24 months (+1.2% and +1.8%). CONCLUSIONS: High-resolution MRI provides a noninvasive reproducible method of tracking changes in carotid atherosclerosis. This pilot study detected changes in individual subjects at both 16 and 24 months. MRI tracking of changes in atherosclerotic plaques should prove useful in assessing vascular disease risk and monitoring the efficacy of interventions designed to induce regression or retard progression.

Aged↗

PubMed2007

White matter fiber tracking computation based on diffusion tensor imaging for clinical applications.

Fiber tracking allows the in vivo reconstruction of human brain white matter fiber trajectories based on magnetic resonance diffusion tensor imaging (MR-DTI), but its application in the clinical routine is still in its infancy. In this study, we present a new software for fiber tracking, developed on top of a general-purpose DICOM (digital imaging and communications in medicine) framework, which can be easily integrated into existing picture archiving and communication system (PACS) of radiological institutions. Images combining anatomical information and the localization of different fiber tract trajectories can be encoded and exported in DICOM and Analyze formats, which are valuable resources in the clinical applications of this method. Fiber tracking was implemented based on existing line propagation algorithms, but it includes a heuristic for fiber crossings in the case of disk-shaped diffusion tensors. We successfully performed fiber tracking on MR-DTI data sets from 26 patients with different types of brain lesions affecting the corticospinal tracts. In all cases, the trajectories of the central spinal tract (pyramidal tract) were reconstructed and could be applied at the planning phase of the surgery as well as in intraoperative neuronavigation.

Adolescent↗

PubMed2005

Image-based cardiac gating for three-dimensional intravascular ultrasound imaging.

Three-dimensional (3-D) intravascular ultrasound (US), or IVUS, provides valuable insight into the tissue characteristics of the coronary wall and plaque composition. However, artefacts due to cardiac motion and vessel wall pulsation limit the accuracy and variability of coronary lumen and plaque volume measurement in 3-D IVUS images. ECG-gated image acquisition can reduce these artefacts but it requires recording the ECG signal and may increase image acquisition time. The goal of our study was to reconstruct a 3-D IVUS image with negligible cardiac motion and vessel pulsation artefacts, by developing an image-based gating method to track 2-D IVUS images over the cardiac cycle. Our approach involved selecting 2-D IVUS images belonging to the same cardiac phase from an asynchronously-acquired series, by tracking the changing lumen contour over the cardiac cycle. The algorithm was tested with IVUS images of a custom-built coronary vessel phantom and with patient images. The artefact reduction achieved using the image-gating approach was > 86% in the in vitro images and > 80% in the in vivo images in our study. Our study shows that image-based gating of IVUS images provides a useful method for accurate reconstruction of 3-D IVUS images with reduced cardiac motion artefact.

Algorithms↗

PubMed2001

Recurrent fuzzy neural network control for piezoelectric ceramic linear ultrasonic motor drive.

In this study, a recurrent fuzzy neural network (RFNN) controller is proposed to control a piezoelectric ceramic linear ultrasonic motor (LUSM) drive system to track periodic reference trajectories with robust control performance. First, the structure and operating principle of the LUSM are described in detail. Second, because the dynamic characteristics of the LUSM are nonlinear and the precise dynamic model is difficult to obtain, a RFNN is proposed to control the position of the moving table of the LUSM to achieve high precision position control with robustness. The back propagation algorithm is used to train the RFNN on-line. Moreover, to guarantee the convergence of tracking error for periodic commands tracking, analytical methods based on a discrete-type Lyapunov function are proposed to determine the varied learning rates of the RFNN. Then, the RFNN is implemented in a PC-based computer control system, and the LUSM is driven by a unipolar switching full bridge voltage source inverter using LC resonant technique. Finally, the effectiveness of the RFNN-controlled LUSM drive system is demonstrated by some experimental results. Accurate tracking response and superior dynamic performance can be obtained because of the powerful on-line learning capability of the RFNN controller. Furthermore, the RFNN control system is robust with regard to parameter variations and external disturbances.

Journal Article↗