Biomedical subjects

Kenneth W Clark

Publications and source records attributed to Kenneth W Clark.

9 recordsLinked to original sources

PubMed2005

Image quality assurance in the prostate, lung, colorectal, and ovarian cancer screening trial network of the National Lung Screening Trial.

The National Lung Screening Trial is evaluating the effectiveness of low-dose spiral CT and conventional chest X-ray as screening tests for persons who are at high risk for developing lung cancer. This multicenter trial requires quality assurance (QA) for the image quality and technical parameters of the scans. The electronic system described here helps manage the QA process. The system includes a workstation at each screening center that de-identifies the data, a DICOM storage service at the QA Coordinating Center, and Web-based systems for presenting images and QA evaluation forms to the QA radiologists. Quality assurance data are collated and analyzed by an independent statistical organization. We describe the design and implementation of this electronic QA system, emphasizing issues relating to data security and privacy, the various obstacles encountered in the installation of a common system at different participating screening centers, and the functional success of the system deployed.

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PubMed2005

Respiratory responses to exposures with fine particulates and nitrogen dioxide in the elderly with and without COPD.

Elderly people, with and without chronic obstructive pulmonary disease (COPD), may be susceptible to particulate matter (PM) air pollution. However, the respiratory impacts of inhaled PM combined with copollutant(s) in controlled exposure studies are unclear and warrant investigation since exposures to PMgas mixtures constitute realistic scenarios. Thus, we exposed 6 healthy subjects and 18 volunteers with COPD (mean age 71 yr) on separate days to (a) filtered air (FA); (b) 0.4 ppm NO2; (c) concentrated ambient particles (CAP), predominantly in the fine (PM2.5) size range, at concentrations near 200 microg/m3; and (d) CAP and NO2 together. Each 2-h exposure included exercise for 15 min every half hour. Most respiratory responses, including symptoms, spirometry, and total and differential counts of induced sputum cells, showed no statistically significant responses attributable to separate or combined effects of CAP and NO2. However, maximal mid-expiratory flow and arterial O2 saturation (measured by pulse oximetry) showed small but statistically significant decrements associated with CAP, greater in healthy than COPD subjects. CAP exposure was also associated with decreased percentages of columnar epithelial cells in sputum. The results suggest that the respiratory effect of the PMNO2 mixture may be primarily PM driven since coexposure to NO2 did not significantly enhance the responses. In conclusion, older adults exposed to urban fine particles may experience acute small-airways dysfunction with impaired gas exchange. Healthy subjects appear more susceptible, suggesting that the respiratory effect may be related to efficient penetration and deposition of inhaled toxic particles in distal small airways. More clinical investigation of the elderly population is warranted.

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PubMed2004

Altered heart-rate variability in asthmatic and healthy volunteers exposed to concentrated ambient coarse particles.

Twelve mildly asthmatic and four healthy adults were exposed to filtered air (FA) and concentrated ambient coarse particles (CCP) supplied to a whole-body exposure chamber via a coarse particle concentrator with 15 parallel virtual impactors. Exposures were conducted in a Los Angeles suburb with high levels of motor-vehicle pollution and lasted 2 h with intermittent exercise. Mean CCP concentration was 157 microg/m(3) (range: 56-218 microg/m(3)) measured by continuous monitoring with a tapered-element oscillating microbalance (TEOM). On average, 80% of mass was coarse (2.5-10 microm aerodynamic diameter) and the rest <2.5 microm. Relative to FA, CCP exposure did not significantly alter respiratory symptoms, spirometry, arterial oxygen saturation, or airway inflammation according to exhaled nitric oxide and total and differential cell counts of induced sputum. After CCP exposure, Holter electrocardiograms showed small (p <.05) increases in heart rate and decreases in heart-rate variability, which were larger in healthy than in asthmatic subjects. Cardiac ectopy did not increase. In conclusion, acute exposure to elevated concentrations of ambient coarse particles elicited no obvious pulmonary effects but appeared to alter the autonomic nervous system of the heart in adult volunteers.

Adult↗

PubMed2003

Tools for managing image flow in the modality to clinical-image-review chain.

Web-based clinical-image viewing is commonplace in large medical centers. As demands for product and performance escalate, physicians, sold on the concept of "any image, anytime, anywhere," fret when image studies cannot be viewed in a time frame to which they are accustomed. Image delivery pathways in large medical centers are oftentimes complicated by multiple networks, multiple picture archiving and communication systems (PACS), and multiple groups responsible for image acquisition and delivery to multiple destinations. When studies are delayed, it may be difficult to rapidly pinpoint bottlenecks. Described here are the tools used to monitor likely failure points in our modality to clinical-image-viewing chain and tools for reporting volume and throughput trends. Though perhaps unique to our environment, we believe that tools of this type are essential for understanding and monitoring image-study flow, re-configuring resources to achieve better throughput, and planning for anticipated growth. Without such tools, quality clinical-image delivery may not be what it should.

Data Display↗

PubMed2003

Controlled exposures of healthy and asthmatic volunteers to concentrated ambient fine particles in Los Angeles.

Information about health effects from controlled exposure to particulate matter (PM) air pollution is relatively limited but potentially critical in urban locations such as Los Angeles, where abundant mobile sources generate combustion-related particles. Nonsmoking healthy (n = 12) and asthmatic (n = 12) volunteers, age 18-45 yr, were exposed to concentrated ambient particulates (CAP) in the fine (PM(2.5)) size range at an average concentration of 174 micro g/m(3) (range 99-224), and to filtered air (FA). Exposures used a two-stage Harvard virtual-impactor concentrator and whole-body chamber and lasted 2 h with alternating rest-exercise periods. Neither group showed significant (p <.05) changes in spirometry or routine hematologic measurements attributable to CAP exposure, relative to FA. Both groups showed CAP-related decreases of columnar cells in postexposure induced sputum, slight changes in certain mediators of blood coagulability and systemic inflammation, and modest increases in parasympathetic stimulation of heart rate variability. Systolic blood pressure decreased in asthmatics and increased in healthy subjects during CAP exposure relative to FA. Cardiovascular (but not respiratory) symptoms increased slightly with CAP in both groups. In summary, the urban fine PM exposures elicited different biologic endpoints with statistically significant differences between CAP and FA. The observed changes in blood inflammation and heart-rate variability were consistent with systemic (rather than respiratory) effects reported from other laboratory and epidemiologic studies. Further studies involving other biologic endpoints, PM size modes, and risk factors will be needed to clarify these results.

Adult↗

PubMed2002

Challenges in image acquisition and distribution for clinical image service.

We have developed a centralized application for acquiring images from multiple picture archiving and communication systems (PACS) and distributing images to a clinical image web server and other repositories. Our flexible strategy addresses a number of administrative challenges associated with delivering images into clinical, research, and test environments. DICOM images flow from PACSs and modalities to a UNIX-based "distributor" application, which relays them to one or more destinations. Image volume and transmission times were collected and analyzed. Three distributors receive an average of 34 gigabytes of image data per day. Images are sent concurrently to two web-based image servers, one used clinically by physicians and one used for testing. Transmission of certain classes of studies is prioritized for key physician groups. Delivery to research systems is also supported. Acquiring images from multi-vendor PACS for distribution to a web server for clinical image viewing is a challenging task. Centralizing the acquisition and distribution process reduces both the administrative effort and the impact on clinical operations associated with maintaining dynamic clinical, testing, and research environments.

Computer Communication Networks↗

PubMed2002

Planning and implementing image delivery to outpatient specialty clinical practices in a large medical center.

Softcopy image viewing using web-based technologies has been deployed to 3 specialty outpatient practices - Lung Center, Neurosurgery, Orthopedic Surgery - where films remain available. Physicians and staff use Philips Easyweb (a web-based image browser) and BJC HealthCare ClinDesk (a Java-based electronic patient record) clients in patient examination rooms and physician workrooms to retrieve images from a Mitra image server. Practice-specific planning and training preceded deployment; on-site training and support came with deployment; on-site and telephone support are available as needed. Softcopy viewing generally is accepted although a few physicians continue to use films. The unavailability of studies performed before the introduction of the image server remains an issue until the server builds a suitable archive. Softcopy-based clinical-image viewing can be supported with web-based technologies, but effective practice-specific planning, training, and technical support are crucial to successful deployment to those accepting softcopy image viewing.

Data Display↗

PubMed2002

Observer study involving laser-digitized versus CCD-digitized images.

We compared laser- and CCD-digitized images for perceived image quality differences in a radiologist-observer study. Films of 50 two- and three-view studies (ankles, chests, c-spines, shoulders) were digitized on calibrated laser (Kodak Lumisys 75) and CCD (VIDAR SIERRA Plus) digitizers. Six radiologists independently compared digitized images on twin high-resolution monochrome monitors. Matching images were randomly presented on left/right monitors to support blinded comparisons. Observers scored image quality (for several diagnostic criteria) as "no different," left or right image "slightly" or "significantly" different. Of 7324 responses, 77.8% scored "no different" and 21.9% "slightly different" (5.9% favoring CCD, 16.0% favoring laser). In only 0.3% did observers score "significantly different." The Lumisys laser images were assessed as only slightly better than VIDAR SIERRA CCD images. Digitizer equipment-selection decisions can, therefore, be considered on the basis of price, reliability, support, ease-of-use, etc., rather than solely on the basis of image quality.

Ankle↗

PubMedDate not supplied

Exposures of elderly volunteers with and without chronic obstructive pulmonary disease (COPD) to concentrated ambient fine particulate pollution.

The elderly and individuals who have chronic obstructive pulmonary disease (COPD) may be sensitive to particulate matter (PM) air pollution. We evaluated short-term health responses of 13 elderly volunteers with COPD and 6 age-matched healthy adults to controlled exposures of ambient PM pollution in suburban Los Angeles. Using a Harvard particle concentrator and a whole-body chamber, we exposed each person on separate occasions to approximately 200 microg/m(3) concentrated ambient particles (CAP) less than 2.5 mum in diameter and to filtered air (FA). Each exposure lasted 2 h with intermittent mild exercise. We found no significant effects of CAP on symptoms, spirometry, or induced sputum. A significant negative effect of CAP on arterial oxygenation (measured by pulse oximetry) immediately postexposure was more pronounced in healthy subjects. Peripheral blood basophils increased after CAP in healthy but not in COPD subjects. In both groups, red cell counts increased slightly 1 day after exposure to FA but not to CAP. Preexposure ectopic heartbeats were infrequent in healthy subjects, but increased modestly during/after CAP exposure relative to FA. Ectopic beats were more frequent in COPD subjects, but decreased modestly during/after CAP relative to FA. Heart-rate variability over multi-hour intervals was lower after CAP than after FA in healthy elderly subjects but not in COPD subjects. Thus, in this initial small-scale study of older volunteers experimentally exposed to ambient PM, some acute cardiopulmonary responses were consistent with effects reported from epidemiologic studies. Unexpectedly, individuals with COPD appeared less susceptible than healthy elderly individuals. Further investigation of older adults is warranted to understand the pathophysiology and public health significance of these findings.

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