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Biomedical subjects

S Grosskopf

Publications and source records attributed to S Grosskopf.

11 recordsLinked to original sources
PubMed2001

Ventricular shape visualization using selective volume rendering of cardiac datasets.

In this paper, we present a novel technique of improving volume rendering quality and speed by integrating original volume data and global model information attained by segmentation. The segmentation information prevents object occlusions that may appear when volume rendering is based on local image features only. Thus the presented visualization technique provides meaningful visual results that enable a clear understanding of complex anatomical structures. In the first part, we describe a segmentation technique for extracting the region of interest based on an active contour model. In the second part, we propose a volume rendering method for visualizing the selected portions of fuzzy surfaces extracted by local image processing methods. We show the results of selective volume rendering of left and right ventricle based on cardiac datasets from clinical routines. Our method offers an accelerated technique to accurately visualize the surfaces of segmented objects.

Algorithms↗
PubMed2001

Comparing teaching and non-teaching hospitals: a frontier approach (teaching vs. non-teaching hospitals).

This paper compares teaching and non-teaching hospitals in terms of their provision of patient services. We proceed by comparing the frontiers of the teaching and non-teaching hospitals using a data envelopment (DEA) type approach, which we apply to a sample of 236 teaching hospitals and 556 non-teaching hospitals operating in the US in 1994. Our results suggest that only about 10% of the teaching hospitals can effectively "compete" with non-teaching hospitals based on the provision of patient services.

Data Collection↗
PubMed2000

[3D models for diagnosis and treatment planning in cardiology].

Due to the development new of imaging devices which produce a large number of tomographic slices, advanced techniques for the evaluation of the large amount of data are required. Computer supported extraction of dynamic 3D-models of the patients anatomy from temporal series thus is highly desirable. Since the diagnostician should be able to quickly make sensible decisions based on the models, high accuracy is required within a minimum of time. We present modeling and visualization techniques that are realized within the Cardiac Station. Results for the application of these techniques to cardiac image data demonstrate their usability. Besides giving information about the patients morphology functional parameters can be derived from the data and visualized together with the model. In order to verify the model with the original image data and for the planning of real intervention interaction techniques are presented.

Anatomy, Cross-Sectional↗
PubMed1997

Productivity growth in health-care delivery.

OBJECTIVES: The authors compute and compare productivity growth in the health-care sectors for a sample of Organization for Economic Cooperation and Development countries over the period from 1974 to 1989. The authors compute Malmquist productivity indexes, which allow productivity growth to be decomposed into efficiency changes and technical change. These indexes also allow the use of primary quantity data (recently available from the Organization for Economic Cooperation and Development), rather than expenditure data, which the authors argue reduces bias resulting from distorted prices. METHODS: The authors specify two models. The first model focuses on the hospital sector; inputs include physicians and medical care beds, whereas outputs are the "intermediate" type used in hospital efficiency studies, namely, inpatient days and discharges. RESULTS: For the 19 countries with complete data, the authors found little productivity growth based on this model (with the exception of Denmark, with 15.4% cumulated growth, and the United States, with about 5% from 1974 to 1989). The authors did find, however, that the highest productivity levels are found in the United States (Italy and Finland were also on the frontier of technology in the base period, 1974). The second model uses the same inputs as the first (but in per capita terms), but it specifies simple proxies of health outcomes as outputs: life expectancy of women at age 40 and the reciprocal of the infant mortality rate. CONCLUSIONS: For the 10 countries with complete data for this model, the authors found evidence of much more widespread and rapid productivity growth: Denmark's cumulated growth was close to 33%, with the United States close behind. In both these countries, this growth was due solely to technical change over this period.

Canada↗
PubMed1997

Virtual reality in the operating room of the future.

In cooperation with the Max-Delbrück-Centrum/Robert-Rössle-Klinik (MDC/RRK) in Berlin, the Fraunhofer Institute for Computer Graphics is currently designing and developing a scenario for the operating room of the future. The goal of this project is to integrate new analysis, visualization and interaction tools in order to optimize and refine tumor diagnostics and therapy in combination with laser technology and remote stereoscopic video transfer. Hence, a human 3-D reference model is reconstructed using CT, MR, and anatomical cryosection images from the National Library of Medicine's Visible Human Project. Applying segmentation algorithms and surface-polygonization methods a 3-D representation is obtained. In addition, a "fly-through" the virtual patient is realized using 3-D input devices (data glove, tracking system, 6-DOF mouse). In this way, the surgeon can experience really new perspectives of the human anatomy. Moreover, using a virtual cutting plane any cut of the CT volume can be interactively placed and visualized in realtime. In conclusion, this project delivers visions for the application of effective visualization and VR systems. Commonly known as Virtual Prototyping and applied by the automotive industry long ago, this project shows, that the use of VR techniques can also prototype an operating room. After evaluating design and functionality of the virtual operating room, MDC plans to build real ORs in the near future. The use of VR techniques provides a more natural interface for the surgeon in the OR (e.g., controlling interactions by voice input). Besides preoperative planning future work will focus on supporting the surgeon in performing surgical interventions. An optimal synthesis of real and synthetic data, and the inclusion of visual, aural, and tactile senses in virtual environments can meet these requirements. This Augmented Reality could represent the environment for the surgeons of tomorrow.

Computer Simulation↗
PubMed1993

Evaluating hospital performance with case-mix-adjusted outputs.

In this article, we compared hospital efficiency using a multiple input-output approach in two ways: one way used a straightforward count of inpatient days and outpatient services as outputs; and the second used a case mix-adjusted count of inpatient services and outpatient care as outputs. Our results show that there was no difference when we incorporated the case-mix index, either as a weighting device or as a separate output. However, this result may be due to our having a relatively homogeneous sample, (i.e., large metropolitan hospitals). Variations using this approach may occur when using a more heterogeneous sample, such as comparing hospitals of all sizes or rural versus urban hospitals.

Bed Occupancy↗
PubMed1992

Association of lifestyle and personality characteristics with blood pressure and hypertension: a cross-sectional study in the elderly.

The association between certain lifestyle and personality characteristics and blood pressure in the elderly was assessed in a cross-sectional study of 843 independent living 60-87 year old volunteers. They comprised 338 women and 505 men of whom 35 and 30% respectively were being treated with antihypertensive drugs. Among untreated volunteers, 28% of women and 28% of men had systolic blood pressure greater than 160 or diastolic blood pressure greater than 95. Isolated systolic hypertension was found in 20% of untreated women and 14% of untreated men. Lifestyle factors and personality characteristics associated with blood pressure were similar to those described in younger adult populations, although there were some differences related to gender and whether subjects were being treated for hypertension. Stepwise multiple regression showed that higher blood pressure was associated with greater body mass index (BMI), alcohol intake and coffee drinking and measures of irritability. Increased physical activity, and high values for measures of suspicion and extraversion were negatively related to blood pressure. Age was positively related to systolic, but not to diastolic blood pressure. The presence of hypertension was significantly associated with self-reports of raised cholesterol, diabetes or angina, as well as past history of heart failure, heart attack or stroke. Thus, in this elderly free-living population blood pressures are still significantly associated with behavioural characteristics which could be further investigated as an alternative or adjunct to antihypertensive therapy.

Aged↗
PubMed1992

Postural fall in blood pressure in the elderly in relation to drug treatment and other lifestyle factors.

In a study of 843 independent-living men and women aged between 60 and 87 in Perth, Western Australia, stepwise multiple regression, after correction for initial levels of systolic blood pressure, showed that postural fall in systolic blood pressure was positively related to alcohol intake of more than 20 ml/day, the use of sleeping tablets and higher levels of anxiety on the Spielberger state-trait scale, and negatively related to body mass index. Postural fall in blood pressure was not significantly related to treatment for hypertension, age, sex, patterns of usual physical activity, tea or coffee drinking, or the diagnosis of diabetes mellitus. This analysis is the first to examine the relationship between lifestyle factors and the magnitude of the fall in systolic blood pressure on standing after adjustment for the association between the change in a variable and its initial level. Our analysis suggests the need for further study of the possible role of lifestyle factors such as the use of sleeping tablets and alcohol in postural hypotension in the elderly.

Aged↗
PubMed1989

A randomised double blind comparison of enalapril versus hydrochlorothiazide in elderly hypertensives.

To assess the suitability of therapy with an angiotensin-converting enzyme inhibitor for older hypertensives, a randomised double blind two group comparison of enalapril (10 to 40 mg daily) with hydrochlorothiazide (25 to 100 mg daily) was carried out in 32 untreated and independently living subjects aged 63 to 82 years with pressures on screening greater than 100 mmHg diastolic or greater than 180 mmHg systolic and after two weeks on placebo greater than 90 mmHg diastolic or greater than 160 mmHg systolic. Twenty-five subjects completed the ten weeks of active treatment with the majority in both groups reaching target blood pressures. Four subjects on enalapril and three on hydrochlorothiazide withdrew because of side effects. Eighteen of the 32 patients volunteered troublesome symptoms they attributed to therapy, which in some instances were alleviated by reductions in drug dosage. Small but significant falls in plasma potassium and sodium and increases in plasma urea and uric acid were seen on hydrochlorothiazide only. It was concluded that although in most cases good blood pressure control can be achieved by enalapril with some advantages over other drugs in the elderly, the potential for adverse effects remains significant. Halving usual starting doses of this and other antihypertensives may help to minimise problems in older subjects.

Aged↗
PubMed1987

Measuring hospital performance. A non-parametric approach.

In this paper a technique for assessing the relative performance of firms is introduced and applied to a sample of hospitals in California. Hospitals are compared on the basis of their relative technical efficiency. The reference technology is constructed from observed outputs and inputs (including physicians) using programming techniques, and efficiency is assessed relative to the frontier of the technology using measures similar to those suggested by Farrell. The technique used here imposes no prespecified functional form, allows for multiple outputs and inputs (allowing for differences in case mix), and yields information on the productive performance of individual hospitals. This technique can also be used to determine whether different types of hospitals use different technologies. Our results, although illustrative rather than definitive, suggest that ownership affects 'efficiency' as measured here: public and NFP hospitals have 'different' best practice frontiers, and public hospitals appear to use relatively fewer resources. These results could reflect differences in quality of care by ownership.

California↗