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PubMed2006

Clouded leopards, the secretive top-carnivore of South-East Asian rainforests: their distribution, status and conservation needs in Sabah, Malaysia.

BACKGROUND: The continued depletion of tropical rainforests and fragmentation of natural habitats has led to significant ecological changes which place most top carnivores under heavy pressure. Various methods have been used to determine the status of top carnivore populations in rainforest habitats, most of which are costly in terms of equipment and time. In this study we utilized, for the first time, a rigorous track classification method to estimate population size and density of clouded leopards (Neofelis nebulosa) in Tabin Wildlife Reserve in north-eastern Borneo (Sabah). Additionally, we extrapolated our local-scale results to the regional landscape level to estimate clouded leopard population size and density in all of Sabah's reserves, taking into account the reserves' conservation status (totally protected or commercial forest reserves), their size and presence or absence of clouded leopards. RESULTS: The population size in the 56 km2 research area was estimated to be five individuals, based on a capture-recapture analysis of four confirmed animals differentiated by their tracks. Extrapolation of these results led to density estimates of nine per 100 km2 in Tabin Wildlife Reserve. The true density most likely lies between our approximately 95 % confidence interval of eight to 17 individuals per 100 km2. CONCLUSION: We demonstrate that previous density estimates of 25 animals/100 km2 most likely overestimated the true density. Applying the 95% confidence interval we calculated in total a very rough number of 1500-3200 clouded leopards to be present in Sabah. However, only 275-585 of these animals inhabit the four totally protected reserves that are large enough to hold a long-term viable population of > 50 individuals.

Animals↗

PubMed1994

How abstract is my thinking as an ethicist in clinical settings?

Answering how abstract my thinking is in practicing applied ethics in clinical settings involves clarifying the idea of abstraction. I see three categories of cases: 1) those I decide automatically, 2) those I feel oblige extra care, and 3) those that force me to abstract thinking in some sense of the word. I use a method for tracking the values at stake in such cases and use it in all three sorts of cases. In consequence, then, to issues about education or training for clinical ethics, I think one needs a method for problem solving that does not seem very abstract but that depends on analyses of some very abstract notions.

Decision Making↗

PubMed2006

Characterization of bacterial growth and the influence of antibiotics by means of UV resonance Raman spectroscopy.

In this work we monitor the bacterial growth of a Bacillus pumilus batch culture by means of UV resonance Raman spectroscopy. Excitation with a wavelength of 244 nm especially enhances the Raman scattering of the aromatic amino acids and the nucleic acid bases and therefore is a good method to track the metabolic changes that occur during bacterial growth. Furthermore, a drug from the fluoroquinolone group is added to the bacterial suspension at the beginning of the exponential growth phase. With the help of chemometrical methods such as hierarchical cluster analysis (HCA) and principal component analysis (PCA) it is possible to visualize the small changes that occur in the UV resonance Raman spectra due to the interaction of the drug with its biological targets DNA and the enzyme gyrase within the bacterial cell.

Anti-Bacterial Agents↗

PubMed2004

Evidence for IHA migration during axial rotation of a lumbar spine segment by using a novel high-resolution 6D kinematic tracking system.

The biomechanical properties of the lumbar spine have long been studied. However, despite its enormous importance, basic functional and morphological properties have been not well understood and require further experimental analysis since data concerning the spatial instantaneous segmental motions are hardly available. This study describes the theoretical background and the technical properties of an innovative method for tracking the instantaneous 3D motion of human spinal segments in vitro at high spatial resolution. This new acquisition system allows to scrutinise closely the location and alignment of the segmental instantaneous helical axis (IHA) and the respective screw pitch as functions of the absolute rotational angle. The required precision of the measuring device was attained (a) by six highly resolving linear inductive displacement sensors in a special spatially configuration (3-2-1), (b) by a method to apply torque and force independently of each other without counteraction, and (c) by suppression of vibrations. The validity and reliability of the experimental set-up and the numerical method of data analysis were tested by subjects of known mechanical properties. In vitro experiments with a human lumbar segment (L3/L4, autopsy material) demonstrated that (a) the IHA migrated during axial rotation from one segmental articulatio zygapophysialis to the other joint, (b) the IHA tilted medial-laterally, and (c) the pitch of the screw altered linearly as a function of the rotational angle. This phenomenon is traced back to the guidance of the articluationes zygapophysiales. The validation of the method allows to map segments of the entire vertebral column. The results can be used as benchmarks for future models of the human spine.

Biomechanical Phenomena↗

PubMed2001

In-vitro assessment of a registration protocol for image guided implant dentistry.

In this study a computer aided navigation technique for accurate positioning of oral implants was assessed. An optical tracking system with specially designed tools for monitoring the position of surgical instruments relative to the patient was used to register 5 partially or completely edentulous jaw models. Besides the accuracy of the tracking system, the precision of localizing a specific position on 3-dimensional preoperative imagery is governed by the registration algorithm which conveys the coordinate system of the preoperative computed tomography (CT) scan to the actual patient position. Two different point-to-point registration algorithms were compared for their suitability for this application. The accuracy was determined separately for the localization error of the position measurement hardware (fiducial localization error-FLE) and the error as reported by the registration algorithm (fiducial registration error-FRE). The overall error of the navigation procedure was determined as the localization error of additional landmarks (steel spheres, 0.5 mm diameter) after registration (target registration error-TRE). Images of the jaw models were obtained using a high resolution CT scan (1.5 mm slice thickness, 1 mm table feed, incremental scanning, 120 kV, 150 mAs, 512 x 512 matrix, FOV 120 mm). The accuracy of the position measurement probes was 0.69 +/- 0.15 mm (FLE). Using 3 implanted fiducial markers, FRE was 0.71 +/- 0.12 mm on average and 1.00 +/- 0.13 mm maximum. TRE was found to be 1.23 +/- 0.28 mm average and 1.87 +/- 0.47 mm maximum. Increasing the number of fiducial markers to a total of 5 did not significantly improve precision. Furthermore it was found that a registration algorithm based on solving an eigenvalue problem is the superior approach for point-to-point matching in terms of mathematical stability. The experimental results indicate that positioning accuracy of oral implants may benefit from computer aided intraoperative navigation. The accuracy achieved compares well to the resolution of the CT scan used. Further development of point-to-point/point-to-surface registration methods and tracking hardware has the potential to improve the precision of the method even further. Our system has potential to reduce the intraoperative risk of causing damage to critical anatomic structures, to minimize the efforts in prosthetic modelling, and to simplify the task of transferring preoperative planning data precisely to the operating room in general.

Algorithms↗

PubMed1999

Dynamic characteristics of laser-Doppler flux data.

Methods for tracking the dynamics of the blood flow microcirculation obtained by laser-Doppler flowmetry (LDF) technique are described. It was shown that LDF signals have complex dynamics. It was mainly characterized by fractal structures and chaos, though multiperiodic, trend-like and stochastic components were also established. Procedures for (i) describing the dynamic structure and (ii) tracking the dynamic changes in time of LDF data are proposed. Examples illustrating the efficiency of these procedures are given using both simulated and LDF data collected in experiments with reactive hyperemia. Irrespective of the universality of the methods, the procedures should be specified according to the problem-oriented clinical and experimental studies.

Algorithms↗

PubMed2003

Pulmonary nodule detection using chest CT images.

PURPOSE: Automated methods for the detection of pulmonary nodules and nodule volume calculation on CT are described. MATERIAL AND METHODS: Gray-level threshold methods were used to segment the thorax from the background and then the lung parenchyma from the thoracic wall and mediastinum. A deformable model was applied to segment the lung boundaries, and the segmentation results were compared with the thresholding method. The lesions that had high gray values were extracted from the segmented lung parenchyma. The selected lesions included nodules, blood vessels and partial volume effects. The discriminating features such as size, solid shape, average, standard deviation and correlation coefficient of selected lesions were used to distinguish true nodules from pseudolesions. With texture features of true nodules, the contour-following method, which tracks the segmented lung boundaries, was applied to detect juxtapleural nodules that were contiguous to the pleural surface. Volume and circularity calculations were performed for each identified nodule. The identified nodules were sorted in descending order of volume. These methods were applied to 827 image slices of 24 cases. RESULTS: Computer-aided diagnosis gave a nodule detection sensitivity of 96% and no false-positive findings. CONCLUSION: The computer-aided diagnosis scheme was useful for pulmonary nodule detection and gave characteristics of detected nodules.

Diagnosis, Computer-Assisted↗

PubMed2004

Does name-based HIV reporting deter high-risk persons from HIV testing? Results from San Francisco.

OBJECTIVE: Name-based HIV reporting has been recommended as a method to track the HIV epidemic but may deter or delay at-risk persons from HIV testing. Previous studies of a deterrent effect of HIV reporting were not conducted in areas with high HIV infection rates and politically active populations. METHODS: In a cross-sectional survey, men who have sex with men (MSM) recruited from gay bars, heterosexuals recruited from the sexually transmitted disease clinic, and injection drug users (IDUs) recruited from street venues were administered a face-to-face anonymous questionnaire. RESULTS: Ninety-four percent of the 118 MSM, 76% of the 99 heterosexuals, and 97% of 105 IDUs surveyed were tested. Six percent of MSM, 9% of heterosexuals, and none of the IDUs correctly identified California's HIV reporting regulations. Of the 75 (25%) participants who thought California had a name-based HIV reporting system, 2 were never tested and 23 had not been tested in the past 12 months. None of those who had never been tested and 2 of those who had not been tested in the past 12 months cited fear of being reported as a reason for not testing recently. CONCLUSION: Fear of reporting is an infrequently cited reason for deterring or delaying testing.

AIDS Serodiagnosis↗

PubMed2005

Noninvasive estimation of tissue temperature via high-resolution spectral analysis techniques.

We address the noninvasive temperature estimation from pulse-echo radio frequency signals from standard diagnostic ultrasound imaging equipment. In particular, we investigate the use of a high-resolution spectral estimation method for tracking frequency shifts at two or more harmonic frequencies associated with temperature change. The new approach, employing generalized second-order statistics, is shown to produce superior frequency shift estimates when compared to conventional high-resolution spectral estimation methods Seip and Ebbini (1995). Furthermore, temperature estimates from the new algorithm are compared with results from the more commonly used echo shift method described in Simon et al. (1998).

Algorithms↗

PubMed2002

Measurement of the thermal coefficients of rewritable phase-change optical recording media.

We describe a method to estimate the heat capacity of the substrate, the dielectric layer, and the phase-change layer of phase-change optical recording media as well as the thermal conductivity of the phase-change layer in its crystalline state. Measurements were carried out on spinning disks with the beam of light focused and locked onto the groove track. The method relies on the identification of the solid-to-liquid phase transition that occurs in the phase-change layer and takes advantage of the dependence of thermal diffusion on track velocity and irradiation time.

Journal Article↗

PubMed2003

Three-dimensional guide-wire reconstruction from biplane image sequences for integrated display in 3-D vasculature.

Using three-dimensional rotational X-ray angiography (3DRA), three-dimensional (3-D) information of the vasculature can be obtained prior to endovascular interventions. However, during interventions, the radiologist has to rely on fluoroscopy images to manipulate the guide wire. In order to take full advantage of the 3-D information from 3DRA data during endovascular interventions, a method is presented that yields an integrated display of the position of the guide wire and vasculature in 3-D. The method relies on an automated method that tracks the guide wire simultaneously in biplane fluoroscopy images. Based on the calibrated geometry of the C-arm, the 3-D guide-wire position is determined and visualized in the 3-D coordinate system of the vasculature. The method is evaluated in an intracranial anthropomorphic vascular phantom. The influence of the angle between projections, distortion correction of the projection images, and accuracy of geometry knowledge on the accuracy of 3-D guide-wire reconstruction from biplane images is determined. If the calibrated geometry information is used and the images are corrected for distortion, a mean distance to the reference standard of 0.42 mm and a tip distance of 0.65 mm is found, which means that accurate guide-wire reconstruction from biplane images can be performed.

Algorithms↗

PubMed2000

DPM, a fast, accurate Monte Carlo code optimized for photon and electron radiotherapy treatment planning dose calculations.

A new Monte Carlo (MC) algorithm, the 'dose planning method' (DPM), and its associated computer program for simulating the transport of electrons and photons in radiotherapy class problems employing primary electron beams, is presented. DPM is intended to be a high accuracy MC alternative to the current generation of treatment planning codes which rely on analytical algorithms based on an approximate solution of the photon/electron Boltzmann transport equation. For primary electron beams, DPM is capable of computing 3D dose distributions (in 1 mm3 voxels) which agree to within 1% in dose maximum with widely used and exhaustively benchmarked general-purpose public-domain MC codes in only a fraction of the CPU time. A representative problem, the simulation of 1 million 10 MeV electrons impinging upon a water phantom of 128(3) voxels of 1 mm on a side, can be performed by DPM in roughly 3 min on a modern desktop workstation. DPM achieves this performance by employing transport mechanics and electron multiple scattering distribution functions which have been derived to permit long transport steps (of the order of 5 mm) which can cross heterogeneity boundaries. The underlying algorithm is a 'mixed' class simulation scheme, with differential cross sections for hard inelastic collisions and bremsstrahlung events described in an approximate manner to simplify their sampling. The continuous energy loss approximation is employed for energy losses below some predefined thresholds, and photon transport (including Compton, photoelectric absorption and pair production) is simulated in an analogue manner. The delta-scattering method (Woodcock tracking) is adopted to minimize the computational costs of transporting photons across voxels.

Algorithms↗

PubMed2004

A comparison of infraclavicular nerve block versus general anesthesia for hand and wrist day-case surgeries.

BACKGROUND: General anesthesia (GA) and brachial plexus block have been used successfully for surgery on the upper extremities. Controversy exists as to which method is more suitable in outpatients undergoing hand and wrist surgery. The authors hypothesized that infraclavicular brachial plexus block (INB) performed with a short-acting local anesthetic would result in shorter time to discharge home as compared with "fast-track" GA. METHODS: After obtaining written informed consent, 52 patients (aged 18-65 yr, American Society of Anesthesiologists physical status I-III) were randomly assigned to receive either an INB or GA under standardized protocols (INB = 3% 2-chloroprocaine + HCO3 + epinephrine 1:300000, followed by propofol sedation; GA = 12.5 mg dolasetron, propofol induction, followed by laryngeal mask airway insertion and desflurane for maintenance; 0.25% bupivacaine for wound infiltration). At the conclusion of the procedure, nurses blinded to the study goals and the anesthetic technique used a modified Aldrete score to decide whether patients could bypass the postanesthesia care unit. Additional data were collected regarding time to postoperative pain, ambulation, home readiness, and incidence of adverse events. RESULTS: More patients in the INB group (79%) met the criteria to bypass the postanesthesia care unit compared with patients in the GA group (25%; P < 0.001). Compared with patients in the GA group, fewer patients in the INB group had pain (visual analog scale score > 3) on arrival to the postanesthesia care unit (3% vs. 43%; P < 0.001). None of the patients in the INB group requested treatment for pain while in the hospital, compared with 48% of patients in the GA group (P < 0.001). Patients in the INB group were able to ambulate earlier (82 +/- 41 min) compared with those in the GA group (145 +/- 70 min; P < 0.001). Time to home readiness and discharge times were shorter for patients in the INB group (100 +/- 44 and 121 +/- 37 min) compared with those in the GA group (203 +/- 91 and 218 +/- 93 min; P < 0.001). Adverse events (e.g., nausea, vomiting, sore throat) occurred less frequently in patients undergoing INB as compared with those undergoing GA. CONCLUSION: Infraclavicular brachial plexus block with a short-acting local anesthetic was associated with time-efficient anesthesia, faster recovery, fewer adverse events, better analgesia, and greater patient acceptance than GA followed by wound infiltration with a local anesthetic in outpatients undergoing hand and wrist surgery.

Adolescent↗

PubMedDate not supplied

Regions of interest tracking in temporal scans based on statistical analysis of gray scale and edge properties and registration of images.

Precise measurement of T1 is needed for its use in temperature monitoring in vivo. Movement of tissue relative to fixed regions of interest can result in large variations in apparent T1, with consequent substantial errors in the measured temperature. This paper evaluates methods of tracking regions of interest as tissue moves during a study in an effort to minimize errors from this cause. Tracking techniques evaluated are based on maintaining constant gray scale levels, locating nearby edges and maintaining position relative to them, and global image registration.

Algorithms↗

PubMed2004

Motion tracking in MR-guided liver therapy by using navigator echoes and projection profile matching.

RATIONALE AND OBJECTIVES: Image registration in magnetic resonance (MR) image-guided liver therapy enhances surgical guidance by fusing preoperative multimodality images with intraoperative images, or by fusing intramodality images to correlate serial intraoperative images to monitor the effect of therapy. The objective of this paper is to describe the application of navigator echo and projection profile matching to fast two-dimensional image registration for MR-guided liver therapy. MATERIALS AND METHODS: We obtain navigator echoes along the read-out and phase-encoding directions by using modified gradient echo imaging. This registration is made possible by masking out the liver profile from the image and performing profile matching with cross-correlation or mutual information as similarity measures. The set of experiments include a phantom study with a 2.0-T experimental MR scanner, and a volunteer and a clinical study with a 0.5-T open-configuration MR scanner, and these evaluate the accuracy and effectiveness of this method for liver therapy. RESULTS: Both the phantom and volunteer study indicate that this method can perform registration in 34 ms with root-mean-square error of 1.6 mm when the given misalignment of a liver is 30 mm. The clinical studies demonstrate that the method can track liver motion of up to approximately 40 mm. Matching profiles with cross-correlation information perform better than with mutual information in terms of robustness and speed. CONCLUSION: The proposed image registration method has potential clinical impact on and advantages for MR-guided liver therapy.

Echo-Planar Imaging↗

PubMed2003

Recovery, visualization, and analysis of actin and tubulin polymer flow in live cells: a fluorescent speckle microscopy study.

Fluorescent speckle microscopy (FSM) is becoming the technique of choice for analyzing in vivo the dynamics of polymer assemblies, such as the cytoskeleton. The massive amount of data produced by this method calls for computational approaches to recover the quantities of interest; namely, the polymerization and depolymerization activities and the motions undergone by the cytoskeleton over time. Attempts toward this goal have been hampered by the limited signal-to-noise ratio of typical FSM data, by the constant appearance and disappearance of speckles due to polymer turnover, and by the presence of flow singularities characteristic of many cytoskeletal polymer assemblies. To deal with these problems, we present a particle-based method for tracking fluorescent speckles in time-lapse FSM image series, based on ideas from operational research and graph theory. Our software delivers the displacements of thousands of speckles between consecutive frames, taking into account that speckles may appear and disappear. In this article we exploit this information to recover the speckle flow field. First, the software is tested on synthetic data to validate our methods. We then apply it to mapping filamentous actin retrograde flow at the front edge of migrating newt lung epithelial cells. Our results confirm findings from previously published kymograph analyses and manual tracking of such FSM data and illustrate the power of automated tracking for generating complete and quantitative flow measurements. Third, we analyze microtubule poleward flux in mitotic metaphase spindles assembled in Xenopus egg extracts, bringing new insight into the dynamics of microtubule assemblies in this system.

Actins↗

PubMedDate not supplied

Sensitivity distributions of impedance cardiography using band and spot electrodes analyzed by a three-dimensional computer model.

Impedance cardiography (ICG) offers a safe, noninvasive, and inexpensive method to track stroke volume estimates over long periods of time. Several modified ICG measurement configurations have been suggested where for convenience or improved performance the standard band electrodes are replaced with electrocardiogram electrodes. This report assesses the sensitivity of the conventional and three modified ICG methods in detecting regional conductivity changes in the simulated human thorax. The theoretical analyses of the measurement sensitivity employ the reciprocity theorem and the lead field theory with a highly detailed, anatomically accurate, three-dimensional computer thorax model. This model is based on the finite-difference element method and the U.S. National Library of Medicine's Visible Human Man anatomy data. The results obtained indicate that the conventional four-band ICG is not specifically sensitive to detect conductivity changes in the region of the heart, aortas, and lungs. Analyzed modified electrode configurations do not reproduce exactly the measurement sensitivity distribution of the conventional four-band ICG. Thus, although the signals measured with modified spot arrangements may appear similar to the four-band configuration, the distribution of the signal origin may not be the same. Changing from band to spot electrodes does not overcome the methodological problems associated with ICG.

Biomedical Engineering↗

PubMed2001

Periodic tallies by regulatory boards: a vital tool for tracking supply in the psychology workforce.

Regulatory boards in psychology and other mental health professions are in key positions to address workforce supply issues. Board data provide real time estimates of the growth within the health professions they regulate. The authors recommend that periodic tallies of the psychology workforce be undertaken through surveys of psychology boards. This will require that boards adopt efficient and standard methods for tracking licensees. Better data from boards would provide longitudinal and cross-jurisdictional comparisons that may enhance efforts to balance supply and demand in the professional workforce and the distribution of psychologists.

Data Collection↗