C. J. Kooijman

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.

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 μm, 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.

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.

Is transluminal coronary angioplasty mandatory after successful thrombolysis? Quantitative coronary angiographic study.

Percutaneous transluminal coronary angioplasty has been advocated as a mandatory procedure to prevent reocclusion after successful thrombolysis in acute myocardial infarction. This study describes our experience with both procedures over a 12 month period. Out of 105 patients catheterised in the acute phase of myocardial infarction, 64 were recanalised with 250 000 units of streptokinase, while in 25 patients recanalisation could not be achieved. In the remaining 16, the infarct related vessel was patent at the time of the procedure. Eighteen of the 78 patients who had a patent infarct related vessel at the end of the recanalisation procedure underwent transluminal angioplasty immediately afterwards. Post lysis angiograms were analysed quantitatively with a computerised measurement system. The contours of the relevant arterial segments were detected automatically. Reference diameter, minimal obstruction diameter, length of the lesions, and percentage diameter stenosis were averaged from multiple views. In 31% of our patients a diameter stenosis of less than 5O0/o was found whereas one of 70% or more was seen in only 19%. Eleven stenotic lesions, recanalised at the acute stage, reoccluded in the short term, and in the long term eight other patients sustained a reinfarction in the same myocardial territory. Seventeen of these 19 recanalised lesions had a diameter stenosis of 580/o or more. In view of these results, we felt justified in combining recanalisation and angioplasty in 18 patients selected from the most recent admissions. In these patients, the mean diameter stenosis decreased from 590/o to 30% and mean pressure gradient from 41 to 8 mmHg. Late follow up showed reocclusion in one

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.

Approaches towards standardization in acquisition and quantitation of arterial dimensions from cineangiograms

Computer-based techniques have been and are being developed to obtain objective and reproducible parameters about the extent and severity of coronary artery disease from coronary cineangiograms. To evaluate changes in arterial dimensions over time repeated cineangiographies need to be performed and analyzed. However, the qualities of both the angiographic investigation and the computer analysis are hampered by various sources of variation.

Computer-Aided Quantitation Of The Severity Of Coronary Obstructions From Single View Cineangiograms

The computer-aided quantitative analysis of co-ronary obstructions from digitized coronary cineangiograms is described. First, the assessment of the percentage diameter reduction from single view angiograms is discussed. This method requires the delineation of the contours of the artery and the analysis of the diameter function. Next, a densitometric method is described to transform the brightness values in the digital image into cali-brated X-ray absorption profiles, thus creating the possibility to assess percentage area reduction of obstructions from single views.

Structural Analysis Of The Coronary Arterial Tree

Computer-aided analysis of coronary cine-angiograms provides ways to extract information about the structure of the coronary arterial tree from these films. The delineation of the coronary tree in sin-gle frames will be described, as well as the assessment of local contraction patterns from two ortho-gonal cine-angiograms. The procedure to detect the coronary tree consists of a gated background subtraction method, followed by a region growing process. The Hilditch-skeleton forms the basis for the construction of an attributed binary tree, where the nodes correspond with bifurcations in the arterial system. Minimum-cost tree-matching procedures on two series of attributed binary trees from two orthogonal cine-angiograms are used for the assessment of local epicardial contraction patterns.

Progression to Complete Coronary Obstruction Without Myocardial Infarction in Patients Who Are Candidates for Percutaneous Transluminal Angioplasty: A 90-Day Angiographic Follow-Up

From September 1980 to September 1982, 153 patients were chosen as good candidates for elective percutaneous transluminal coronary angioplasty (PTCA). All had disabling but stable angina pectoris and proximal stenosis of a major coronary artery suitable for balloon dilation.

ARTERY DETECTION AND ANALYSIS IN CINE-ANGIOGRAMS

A coronary cine-angiogram is a sequence of roentgen absorption images, where each frame represents the two-dimensional projection of the coronary arterial system at a given instant in the cardiac cycle. New developments in our laboratory in the field of quantitative coronary angiography have been directed towards frame-to-frame analysis of the entire coronary tree. In the first frame of a series of cineframes to be analyzed, a tentative centerline of a major vessel is found with a controlled tracing routine, followed by minimum cost contour detection. In subsequent frames the segmentation process is guided by utilizing a priori information, represented in terms of a structured model of the arterial system. As a result of this guidance, user interaction may be reduced to a minimum. The controlled maxtracing procedure has been found to be useful in other applications as well, e.g. in retinal angiography, as illustrated in this paper.