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PubMed2000

Moving to global standards for accreditation processes: the ExPeRT Project in a larger context. External Peer Review Techniques.

The ExPeRT (External Peer Review Techniques) Project, a European Union effort to examine and compare methods of health care evaluation currently in use, includes an assessment of accreditation as one such method. This article contributes to that examination by describing recent work, through the International Society for Quality in Health Care (ISQua), to investigate and to enhance the international comparability of national health care accreditation programs, both existing and newly emerging.

Accreditation↗

PubMedDate not supplied

[Health workforce forecasting carried out by the C.S.D.M. (1964-2004)].

During the last 4 decades, the Centre has performed 16 pieces of forecast on the various health professions in France, the majority being devoted to medical doctors. During the 60's, information were scarce, and calculations on both the inflows of future new graduates and the outflows of future deaths and retirements could not reach an acceptable level of relevance. In 1972, a numerus clausus system was established at the beginning of medical training. Moreover, efforts were deployed to collect better data and improve projection techniques. All these factors contributed to raise strongly the quality of the forecasting work. The discrepancies between the projected and actual trends were narrowing, as showed below: [table: see text] The forecasts were based on the demographic projection techniques and the results obtained showed not only the total number of active physicians in the country but equally the distribution by age groups of this total number. The latter element allows the predictions of the aging process of the medical profession as an impact of the present-day policies concerning medical student intake (numerus clausus).

Female↗

PubMed2004

New laboratory technique measures projected dynamic area of prosthetic heart valves.

BACKGROUND AND AIM OF THE STUDY: Fluid dynamic forces, valve design factors and gravity interactively determine the complex motion of prosthetic heart valve occluders. Although motion has been investigated, in vitro, using high-speed image recording, the technique has significant cost and limitations on resolution. METHODS: The kinematics of mechanical and biological valve occluders in the aortic and mitral positions were assessed by measuring projected dynamic valve area (PDVA). Valves were tested in a pulse duplicator system simulating normal cardiac conditions. To quantify PDVA, light passage through back-illuminated valves was measured by a calibrated photosensor with high-frequency response up to 150 kHz. Ten consecutive cycles were sampled using a PC data acquisition system. The system was calibrated under static conditions using reference areas. RESULTS: Several characteristics can be obtained from PDVA measurement including: maximum and minimum PDVA; rate of change of valve opening and closing PDVA; occluder rebound; and oscillatory open occluder behavior. Biological valves open more rapidly, close more gently, and exhibit no occluder rebound. They are also unaffected by gravity, and vary little in behavior from cycle to cycle compared with mechanical valves. CONCLUSION: A new method for measuring PDVA has been developed. Distinct differences in performance between valves were identified. It is hypothesized that, aside from patient factors and differences in materials, mechanical valves that mimic the PDVA behavior of biological valves, will lead to reduction of thrombogenicity, cavitation and high-intensity transient signals (HITS), and also reduce sound level and regurgitation.

Coronary Circulation↗

PubMed1981

[The use of electrophysiological techniques to project typical psychotropic drug effects: some examples (author's transl)].

A long existing hypothesis, i.e. that the EEG effects, in lead O2A2, of typical psychotropic drugs are substance class specific, when given as single oral dosages to healthy volunteers, is discussed. Using the technique of pharmacoelectroencephalograhpy, five typical representatives of neuroleptics, anxiolytics, antidepressives, psychostimulants (Fig. 2) as well as placebo were investigated in 75 volunteers, each receiving one representative of each substance class in a double blind 5-fach change over latin square design (Fig. 3). A five minute EEG record for lead O2A2 was obtained pre, 1 h and 3 hrs post drug intake unter RR (Relaxed Recording) conditions. Typical samples of th EEG records are shown in Figs. 4--7. Parametrisation was done using power spectrum analysis. Then 3 x 7 target variables were formed--six relative power values in predetermined frequency bands and the total power between 1.5 and 30.0 Hz for 3 occasions of measurement (Fig. 4--7). Using a (five-group) linear discriminant analysis the substance effects on the EEG were transformed into 5 probability measures for the five substance classes (Fig. 4--7). The present paper should provide a demonstration of some typical examples, using single subjects, of the projection of substance effects onto an electrophysiological level using a vector of 21 components (7 target variables for 3 occasions of measurement) as can be seen from Table 1. Furthermore, the transformation into probability measures of the five substance classes are shown in Table 2. Table 3 shows five examples of projections of substance effects, which do not fit into the classifications to which they belong. An attempt is made to explain, whether single target variables from the power spectrum can contribute differently to the discrimination between single substances of different substance classes. Within the accepted system of 4 psychotropic drug classes, the following variables seem to be of importance: a) The benzodiazepine anxiolytics show a marked increase in beta F1 (12.0--18.0 Hz) power and activity and, related to sedation, an increase in delta F-power and a decrease in alpha-power; b) The psychostimulants of the amphetamine type show an increase in total power and alpha-power, an increase in the power of the frequency ranges near to the alpha-band (slow beta, fast theta) and a decrease in delta F (1.5--5.5 Hz)-power, when delta F-power is high in the pre-values, indicating a stabilization in vigilance; c) The neuroleptics show a marked increase in theta F (5.5--8.5 Hz)-power, some increase in the delta F--and a decrease in the beta F1-and beta F3-power; d) Tricyclic antidepressants show an interaction between delta F-theta F-, alpha- and beta-power, in the sense of a dissociative shift in vigilance.

Adult↗

PubMed2000

The oblique radiographic technique for bone height measurements on edentulous mandibles: a preclinical study and an introduction to the clinical use.

OBJECTIVE: The aim of this study was to quantify the effect of mandibular angulation, position, and shape of the edentulous mandible on the distortion of its image on lateral oblique radiographs in a preclinical study. Suggestions for the clinical use of this technique are made. STUDY DESIGN: Five edentulous dry mandibles were used, varying in size from small to wide and equipped with metal bars in and on top of the mandible. The mandibles were radiographed at 9 different positions by tilting the mandible around the intercondylar axis and by using the oblique projection technique in a cephalostat. RESULTS: The length of the images of the metal bars varied significantly when we tilted the mandibles from 20 degrees to -20 degrees. As a result of the effects of magnification and distortion, the image size varied from between 0.96% and 1.06% of the real size. Neither the size of the mandible nor the position of the bars was related to the degree of magnification. CONCLUSION: The oblique projection technique has limited geometric errors in depicting the edentulous mandible. For evaluative bone height measurements in patients with extremely resorbed mandibles treated with dental implants, it is a promising technique if the patient (specifically the mandible) can be positioned reproducibly in the apparatus.

Analysis of Variance↗

PubMed2005

Priorities in optimisation of medical X-ray imaging--a contribution to the debate.

A simplistic approach to optimising medical imaging is to use the lowest effective dose to the patient that does not jeopardise a correct diagnosis. With limited resources and over 1000 different types of X-ray examinations, it is not always easy to set the right priorities and to decide how to perform the optimisation. Recent research shows that the 'Rose model' for the detection of specific structures does not hold for realistic backgrounds. A reasonable conclusion regarding methods for optimisation is therefore not to use contrast-detail phantoms. Phantoms producing clinically realistic background images or real clinical images-modified with respect to quantum noise levels-are preferred. The images should be evaluated using visual grading or receiver operating characteristic methods. The quality of many common X-ray investigations, performed with projection techniques, is not limited by quantum noise. For these, the radiation dose to the patient can be lowered without seriously affecting the outcome of the detection task. For computed tomography (CT) investigations, the obscuring effect of anatomical structures and anatomical noise is less pronounced than in projection techniques. For CT, true optimisation in terms of a trade-off between radiation dose and image quality is therefore more likely to be effective. Both the number of CT examinations performed per year and the effective dose per examination are increasing owing to the technical advances in CT--jointly leading to a steady increase in the collective dose from CT examinations. Moreover, the smaller influence of the anatomical background in CT gives a high correlation between detection tasks and radiation dose. Thus, a reasonable view to take on which examinations to optimise is to give priority to CT examinations. The recommended distribution of a full working week for optimisation, based on the relative lifetime risk of lethal cancer from diagnostic X rays and the total collective dose from CT, is to use three out of five days to optimise CT examinations, of which one day should be devoted to paediatric CT.

Adult↗

PubMed1999

The human vector magnetogastrogram and magnetoenterogram.

Electrical activity in the gastrointestinal system produces magnetic fields that may be measured with superconducting quantum interference device magnetometers. Although typical magnetometers have detection coils that measure a single component of the magnetic field, gastric and intestinal magnetic fields are vector quantities. We recorded gastric and intestinal magnetic fields from nine abdominal sections in nine normal human volunteers using a vector magnetometer that measures all three Cartesian components of the magnetic field vector. A vector projection technique was utilized to separate the magnetic field vectors corresponding to gastric and intestinal activity. The gastric magnetic field vector was oriented in a cephalad direction, consistent with previously observed data, and displayed oscillatory characteristics of gastric electrical activity (f = 3.03 +/- 0.18 cycles/min). Although the small bowel magnetic field vector showed no consistent orientation, the characteristic frequency gradient of the small bowel electrical activity was observed. Gastric and intestinal magnetic field vectors were oriented in different directions and were thus distinguished by the vector projection technique. The observed difference in direction of gastric and intestinal magnetic field vectors indicates that vector recordings dramatically increase the ability to separate physiological signal components from nonphysiological components and to distinguish between different physiological components.

Analog-Digital Conversion↗

PubMed1977

Basic principles of computed axial tomography.

Computer tomography (CT) is a radiological imaging method which yields transverse tomographic images reflecting with high accuracy the spatial distribution of x-ray attenuation in the part examined. The contrast resolution achieved by CT permits the visualization of soft tissue structure heretofore invisible with conventional radiographic procedure. The CT image is reconstructed by a computer applied algorithm, from a series of x-ray attenuation measurements obtained at different angles around the subject, by means of radiation detectors; The signal to noise ratio for these measurements is optimized by reducing the contribution of scattered radiation and of system noise. The CT principle of image reconstruction is also applicable in nuclear medicine imaging, with the goal of achieving contrast improvement and quantitative assessment of radionuclide distribution over conventional "projection" techniques. In this application, however, the attenuation of the radiation in the tissue interposed between the radionuclide and the detector must be taken into account to yield quantitatively accurate images. Furthermore, the variation of the field of view of the collimator as a function of distance contributes another unwanted variable to the reconstruction process. A mathematically rigorous tomographic reconstruction which would account for these variables is unavailable for gamma ray-emitting radionuclides, although approximate solutions of that problem have led to the satisfactory images of the head. Images of larger inhomogeneous organs are less quantitative. The detection of coincidence annihilation counting of positron-emitting radionuclides allows the accurate correction for the attenuation of that radiation in tissues and permits depth independent collimation which renders these radionuclide particularly suitable for their imaging by CT. A number of CT devices designed for the imaging of positron emitting radionuclides are yielding nuclear medicine images of quality and potential clinical usefulness unequaled by more conventional projection techniques.

Radionuclide Imaging↗

PubMed1977

Densitometric analysis of experimentally produced periapical radiolucencies.

Artificial periapical lesions were created in a mounted dried human mandible. These lesions were radiographed by means of a reproducible projection technique. A penetrometer was projected on the same radiographs as the dental and bony structures. The developing process was standardized. The radiographs were evaluated by means of densitometric analysis. The densitometer readings of the dental and bony structures on the radiographs were converted to a millimeters-of-aluminum-equivalents scale by means of the densitometer readings of the penetrometer images on the same radiographs. The measurements on the radiographs were presented in graphs and isodensitometric images. Areas where bone was removed could be reproducibly distinguished by densitometric analysis from areas where no bone was removed. For this purpose, the densitometric analysis of periapical radiographs proved to very useful, whereas the interpretations of the same radiographs by ten dentists differed greatly.

Densitometry↗

PubMed1956