Sending specialist reports to GPs using EDI.

This paper describes a project in which specialist reports are sent to general practitioners using EDI. The reports were protocolled to better meet the wishes of the GPs. This also made it possible to achieve a further structurization of the existing EDI-message, using free-text qualifiers. Future developments of specialist-GP communication are discussed, specifically regarding the integration of their electronic medical records. It is concluded that EDI can and will play an important role in this.

Extraction, preparation, and presentation of patient classification-data for the benefit of management overviews.

In the Free University Hospital, the nursing staff enters data daily into the computerized patient classification system. The computer calculates and gives a retrospective overview of the patient workload per day and per nursing unit. The present system does not comply with the information needs of the middle and higher management. This is due to differences in the manner of working on the various nursing units. For these reasons, the patient classification data was extracted from the central HIS database and copied to a PC environment. Here, the data was further ordered and processed to produce overviews for the nursing management. This was done by developing a user friendly interface with the spreadsheet program QuattroPro.

How critical is frame selection in quantitative coronary angiographic studies?

To analyse quantitatively a coronary arterial segment from a cineangiogram, an end-diastolic or neighbouring frame is usually selected. However, different cardiologists may select other (although usually neighbouring) frames, even when the same selection criteria are followed. It is also possible that the frames are selected from different cardiac cycles. In this study the effects of such phase shifts on the reproducibility of the quantitative measurements were studied. In a total of 38 consecutive patient films obtained at a filmspeed of 25 frames s-1, the frame phi demonstrating the severity of a lesion optimally as judged by a senior cardiologist, the three preceding frames, the three following frames and one frame exactly one cycle prior to or following frame phi were selected; frame phi was always chosen in the end-diastolic phase of the cardiac cycle. In each film one coronary arterial segment with a focal lesion was analysed quantitatively in these total of 8 frames with the Cardiovascular Angiography Analysis System (CAAS). No significant differences were found in the mean difference and the standard deviations of the differences (variabilities) in the obstruction diameter, interpolated reference diameter, percent diameter stenosis, extent of the obstruction and area of atherosclerotic plaque obtained in the various frames with respect to frame phi. Therefore, it may be concluded that the selection of a cineframe for quantitative analysis in the end-diastolic phase of the cardiac cycle is not very critical.(ABSTRACT TRUNCATED AT 250 WORDS)

Variabilities in measurement of coronary arterial dimensions resulting from variations in cineframe selection.

To quantitatively analyze a coronary arterial segment from a cineangiogram, an end-diastolic or neighboring cineframe is usually selected, such that a possibly existing coronary lesion is visualized optimally, as judged by the cardiologist. However, different cardiologists may select different (although usually neighboring) frames, even when following the same selection criteria. It is also possible that the frames are selected from different cardiac cycles. In this study the effects of such phase shifts on the reproducibility of the quantitative measurements were studied. In a total of 38 consecutive patient films obtained at a filmspeed of 25 frames/sec, the frame 0 demonstrating the severity of a lesion optimally, as judged by a senior cardiologist, the three preceding frames, the three following frames and one frame exactly one cycle prior to or following frame 0 were selected; frame 0 was always chosen in the end-diastolic phase of the cardiac cycle. In each film one coronary arterial segment with a focal lesion was analyzed quantitatively in these eight frames with the Cardiovascular Angiography Analysis System (CAAS). No significant differences were found in the mean difference and the standard deviations of the differences (variabilities) in the obstruction diameter, interpolated reference diameter, percent diameter stenosis, extent of the obstruction and area of atherosclerotic plaque obtained in the various frames with respect to frame 0. Therefore, it may be concluded that the selection of a cineframe for quantitative analysis in the end-diastolic phase of the cardiac cycle is not very critical; in other words, the obstruction measurements are not time-dependent for frames in the end-diastolic phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative angiography of the left anterior descending coronary artery: correlations with pressure gradient and results of exercise thallium scintigraphy.

To evaluate, during cardiac catheterization, what constitutes a physiologically significant obstruction to blood flow in the human coronary system, computer-based quantitative analysis of coronary angiograms was performed on the angiograms of 31 patients with isolated disease of the proximal left anterior descending coronary artery. The angiographic severity of stenosis was compared with the transstenotic pressure gradient measured with the dilation catheter during angioplasty and with the results of exercise thallium scintigraphy. A curvilinear relationship was found between the pressure gradient across the stenosis (normalized for the mean aortic pressure) and the residual minimal area of obstruction (after subtracting the area of the angioplasty catheter). This relationship was best fitted by the equation: normalized mean pressure gradient = a + b . log [obstruction area], r = .74. The measurements of the percent area of stenosis (cutoff 80%) and of the transstenotic pressure gradient (cutoff 0.30) obtained at rest correctly predicted the occurrence of thallium perfusion defects induced by exercise in 83% of the patients.

Assessment of short-, medium-, and long-term variations in arterial dimensions from computer-assisted quantitation of coronary cineangiograms.

A computer-assisted technique has been developed to assess absolute coronary arterial dimensions from 35 mm cineangiograms. The boundaries of optically magnified and video-digitized coronary segments and the intracardiac catheter are defined by automated edge-detection techniques. Contour positions are corrected for pincushion distortion. The accuracy and precision of the edge detection procedure as assessed from cinefilms of contrast-filled acrylate (Perspex) models were -30 and 90 micrometers, respectively. The variability of the analysis procedure itself in terms of absolute arterial dimensions was less than 0.12 mm, and in terms of percentage arterial narrowing for coronary obstructions less than 2.74%. Short-, medium-, and long-term variability measurements were assessed from repeated coronary angiographic examinations performed 5 min, 1 hr, and 90 days apart, respectively. For all studies the mean differences in absolute diameters were less than 0.13 mm. The variability in obstruction diameter ranged from 0.22 mm for the best-controlled study (medium-term) to 0.36 mm for the least-controlled study (long-term); variability in reference diameter ranged from 0.15 to 0.66 mm, respectively. It is concluded that the biological variations are a source of major concern and that further attempts toward standardization of the angiographic procedure are seriously needed.

Assessment of dimensions and image quality of coronary contrast catheters from cineangiograms.

In the quantitative assessment of coronary arterial dimensions from coronary cineangiograms, the contrast catheter is usually used as a scaling device, requiring the definition of the catheter contours by semi- or fully automated contour detection procedures. The image quality of the x-ray radiated catheter is dependent on the catheter material, concentration of the contrast agent in the catheter, and kilovoltage of the x-ray source. The effects of these variables on the image quality and accuracy of the size-measurement of the filmed catheters were studied for four different catheter materials: woven dacron (wd), polyvinylchloride (pv), polyurethane (pu), and nylon. The following parameters were studied: measured size, image contrast, and average brightness gradient along the edges of the displayed catheters. The average differences of the angiographically measured size with the true size for the wd, pv, pu, and nylon catheters were +0.2, -3.2, -3.5, and +9.8%, respectively. The image contrast at various fillings of the catheters was roughly identical for the wd, pv, and pu catheters, and significantly lower for the nylon catheter. Image gradient was highest for the wd catheter, followed by the pv and pu catheters, and lowest for the nylon catheter. From these data it may be concluded that the woven dacron catheter is most suitable for quantitative coronary angiographic studies. The polyvinylchloride and polyurethane catheters perform about equally well but slightly less than the woven dacron catheter. The nylon catheter should not be used for such quantitative studies.

Assessment of percutaneous transluminal coronary angioplasty by quantitative coronary angiography: diameter versus densitometric area measurements.

Cineangiograms of 138 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) were analyzed with a computer-based coronary angiography analysis system. The results before and after dilatation are presented. In a first study group (120 patients), the severity of the obstructive lesions derived from the automatically detected contours was evaluated in absolute terms and in percent-diameter reduction. In a second group of patients, 18 coronary lesions were selected for their extreme severity and symmetric aspect before angioplasty as assessed from multiple views. In the second group, the densitometric percent-area stenosis was used to assess the changes in cross-sectional area after PTCA and was compared with the circular percent-area stenosis computed from the diameter measurements. Before PTCA, a good agreement exists between the densitometric percent-area stenosis and the circular percent-area stenosis. After PTCA, important discrepancies between these 2 types of measurements are observed. It is suggested that these discrepancies in results after PTCA can be accounted for by asymmetric morphologic changes in luminal cross section, which cannot be assessed accurately from diameter measurements in a single-plane view.

Coronary artery dimensions from cineangiograms methodology and validation of a computer-assisted analysis procedure.

To evaluate the efficacy of modern therapeutic procedures in the catheterization laboratory, the effects of vasoactive drugs, as well as the effects of short and long term interventions on the regression or progression of coronary artery disease, an objective and reproducible technique for the assessment of coronary artery dimensions was developed. This paper describes the methodology of such a computer-assisted analysis system, as well as the results from a validation study on the accuracy and precision. A region in a 35 mm cineframe encompassing a selected arterial segment is optically magnified and converted into video format by means of a specially constructed cinevideo converter and digitized for subsequent analysis by computer. Contours of the arterial segment are detected automatically on the basis of first and second derivative functions. Contour data are corrected for pincushion distortion; arterial dimensions are presented in mm, where the calibration factor is derived from a computer-processed segment of the contrast catheter. The accuracy and precision of the edge detection procedure as assessed from cinefilms of perspex models (%-D stenosis =/<70 percent) filled with contrast agent were -30 and 90 mum, respectively. The variablity of the analysis procedure by itself in terms of absolute arterial dimensions was less than 0.12 mm, and in terms of percentage arterial narrowing for coronary obstructions less than 2.74 percent. It is concluded that this system allows the measurement of coronary arterial dimensions in an objective and highly reproducible way.