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J H Reiber

Publications and source records attributed to J H Reiber.

At least 91 records · Page 5Linked to original sources
PubMed1995

Effect of data compression on quantitative coronary measurements.

Digital coronary and left ventricular angiography demand high transfer rates and very large data storage if all the clinical data are to be achieved. If appropriate compression schemes were available without compromising the quality and resolution of the image data, such demands could be lessened. In this study we compared the influence of different compression factors of the Adaptive Real Time Image Compression (ARTIC) scheme used on the Philips DCI-SX systems on coronary measurements assessed with the Automated Coronary Analysis (ACA) package. Loss-free acquired images of size 512(2) x 8 bits, which had been stored digitally on tape, were reloaded into the DCI with compression factors of 2, 3, and 4; only the factor 2 is loss free. To evaluate the effect of the different data compressions on the accuracy of the measurements, the diameters of a vessel phantom (tube sizes ranging from 0.687 to 5.062 mm) were determined. To evaluate the reproducibility of the results, the intraobserver variability was determined for the different compression factors from 40 coronary obstructions. The differences in the reference diameter measurements of the vessel phantom were -0.03 +/- 0.06 mm, 0.01 +/- 0.07 mm, and 0.04 +/- 0.08 mm for the compression factors 2 (loss free), 3, and 4, respectively. The results were not statistically significantly different. The intraobserver variabilities in the obstruction diameter measurements of the coronary obstructions were -0.04 +/- 0.13 mm, 0.00 +/- 0.14 mm, and 0.02 +/- 0.13 mm for the compression factors 2, 3 and 4, respectively. The intraobserver variabilities in the reference diameter measurements were -0.02 +/- 0.12 mm, 0.01 +/- 0.09 mm, and 0.03 +/- 0.09 mm for the compression factors 2, 3, and 4, respectively. The intraobserver variabilities of the percent diameter stenosis were 0.96 +/- 4.19%, -0.01 +/- 4.88% and -0.04 +/- 4.68% for the compression factors 2, 3, and 4, respectively. None of these differences were statistically significant. Both from a qualitative and quantitative point of view, data compression factors 3 and 4 are acceptable in digital coronary arteriography.

Coronary Angiography↗
PubMed1995

Quantitative analysis of regional left ventricular function after myocardial infarction in the pig assessed with cine magnetic resonance imaging.

To assess the accuracy of quantitative analysis of global and regional wall motion and wall thickening of the left ventricle with cine magnetic resonance (MR), images obtained in eight pigs before and after myocardial infarction were compared with those obtained using gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA)-enhanced multislice spin-echo MR imaging and determination of pathology. The region with abnormal wall motion and wall thickening, as determined with cine MR imaging, identified the same region of infarction as indicated by Gd-DTPA-enhanced spin-echo MR imaging and pathology. Within the infarcted region wall motion and wall thickening analyzed with the centerline method were significantly reduced. We conclude that the use of quantitative analysis of cine MR images accurately determines localization and extent of regional left ventricular dysfunction in the infarcted heart in vivo. This analysis using dedicated software including the centerline method allows sequential assessment of regional left ventricular function in normal and infarcted hearts.

Animals↗
PubMed1995

The influence of image enhancement and reconstruction on quantitative coronary arteriography.

In the coming years, cinefilm will gradually be replaced by some digital medium for the archiving of angiographic images. However, not only the question which digital archiving medium will be used in the future is important, but also which images are to be stored. Options are to either archive the raw, unprocessed images, or the enhanced images as they are displayed on the viewing monitor in the catheterization laboratory. In the first case, an off-line workstation will need additional hardware to display the images with the same image quality as they were acquired; in the second case, the question remains whether quantitative analysis programs still provide reliable results. Goal of this study was to investigate the possible effects of image enhancement and reconstruction on the results from quantitative coronary arteriographic (QCA) measurements with the Philips ACA-package (Automated Coronary Analysis). Image enhancement was achieved by an unsharp masking approach; the reconstruction of the original image from the enhanced image was attempted by an iterative deconvolution approach. The evaluation study consisted of two parts; a technical evaluation on eleven phantom tubes with known dimensions, and a clinical evaluation study on 48 coronary lesions. The results of the technical evaluation demonstrate that the measurement errors increase for the smaller vessel sizes (< 1.2 mm) when QCA is applied to reconstructed images. The systematic difference on the smallest phantom tube (0.687 mm) on unprocessed images was limited to 0.050 mm, while it increased to 0.089 mm for the reconstructed images. Moreover, the random differences for the smaller vessel sizes increased for all processed images: for 0.159 mm for the unprocessed image to 0.189 mm for the enhanced and 0.204 mm for the reconstructed image (p < 0.01). For the larger vessels, in general, no significant differences could be observed between the results of the unprocessed and processed images. The results of the clinical evaluation study demonstrate that especially the obstruction diameter is overestimated when QCA is applied to reconstructed images (0.113 mm). Although the measurements on the enhanced images did not show a significant overestimation of the obstruction diameter, the intra-observer random difference was much higher (0.199 mm for the enhanced images versus 0.140 mm for the unprocessed images, p < 0.01). In more general terms, applying QCA on enhanced images increases the random difference values, while reconstructing the original image from the enhanced images increases the systematic errors in the measured diameters. This study has clearly demonstrated that especially the smaller diameter values (< 1.2 mm) are influenced by image enhancement. Therefore, to obtain quantitative results with the desired small values for systematic and random differences, requires that the raw, unprocessed image data be archived.

Computer Systems↗
PubMed1995

Quantification of right ventricular function with magnetic resonance imaging in children with normal hearts and with congenital heart disease.

In clinical treatment of children with congenital heart disease (CHD) assessment of right ventricular (RV) function is important. Available imaging techniques have been of limited value because of technical factors and the complex geometry of the right ventricle. To validate magnetic resonance (MR) imaging measurements of RV function in children, gradient echo MR imaging of both ventricles and MR flow mapping of great vessel and tricuspid flow was performed in 20 children with CHD affecting the right ventricle and in 22 healthy children ranging in age from 5 to 16 years. Close correlation between RV versus LV stroke volumes (r = 0.96) and RV stroke volume versus great artery (r = 0.97) or tricuspid flow (r = 0.97) was observed with small interobserver and intraobserver variability. Results of healthy children were end-diastolic volume: 70 +/- 9 ml/m2, end-systolic volume: 21 +/- 5 ml/m2, and ejection fraction: 70% +/- 4%. In the patient groups clinically important differences were noted. We conclude that MR imaging provides accurate noninvasive measurements of RV function in healthy children and patients with (operated) CHD.

Adolescent↗
PubMed1995

Influence of the selection of angiographic projections on the results of coronary angiographic follow-up trials. International Nifedipine Trial on Antiatherosclerotic Therapy Investigators.

In recent years follow-up trials on coronary artery disease with angiographic end points analyzed quantitatively have gained increasing relevance and popularity. There is no consensus, however, on the method of calculation of progression or regression from multiple angiographic projections. Therefore the influence of the selection of angiographic projections on the outcomes of such trials was investigated with the data of the International Nifedipine Trial on Antiatherosclerotic Therapy. In 348 patients with coronary artery disease, repeated coronary angiograms were compared in multiple identical angiographic projections. Changes in angiographic parameters were averaged over the 1063 stenoses analyzed. Five methods of evaluation of multiple projections in the individual stenoses were applied, resulting in different extents of overall progression, or even regression of coronary artery disease (p < 0.01). It is concluded that in quantitative coronary angiographic follow-up trials changes should be averaged over all angiographic projections available for a stenosis to avoid overestimation of progression or regression.

Analysis of Variance↗
PubMed1995

Automated contour detection and acoustic quantification.

Echocardiographic left and right ventricular sequences are usually interpreted visually, but current quantitation techniques have been found to be tedious, time-consuming and associated with significant inter- and intra-observer variabilities. In an attempt to eliminate these problems, we have developed the Echocardiographic Analysis System (EAS) which uses robust automated border detection techniques both for single frames as well as for sequences. Comparison of LV cross-sectional area with the semi-automated border detection (AUTO) and those assessed from manual tracings (MAN) yielded a systematic difference (MAN-AUTO) of -6.6% (p < 0.001), and a random difference (standard deviation of paired signed differences) of 11.8%. Current developments are directed towards real-time automated border detection with an Accelerator board, integration of Acoustic Quantification (AQ) data as edge information into EAS, and intravascular echocardiographic applications.

Computers↗
PubMed1995

Angiographic findings and catheterization laboratory events in patients with primary coronary angioplasty or streptokinase therapy for acute myocardial infarction.

BACKGROUND: The purpose of this study was to evaluate catheterization laboratory events and angiographic findings in patients randomly assigned to undergo primary coronary angioplasty or to receive intravenous streptokinase for acute myocardial infarction. METHODS: We analysed angiographic data in 301 patients with acute myocardial infarction, randomly assigned to undergo primary coronary angioplasty without antecedent thrombolytic therapy or to receive intravenous streptokinase therapy. Follow-up coronary angiography was preferably performed after 3 months. All angiograms were analysed with a quantitative coronary analysis system. RESULTS: Of the 152 patients assigned to angioplasty treatment, 140 underwent this procedure with a success rate of 97%. The residual diameter stenosis of the infarct-related vessel immediately after angioplasty was 27 +/- 15% and there were major events in 14% of the patients in the catheterization laboratory. At follow-up angiography after a mean interval of 92 days in the angioplasty assigned patients, a diameter stenosis of 35 +/- 22% was observed in this group. The restenosis rate was 28% and the reocclusion rate 5%. A Thrombolysis in Myocardial Infarction (TIMI) grade 2 flow immediately after angioplasty was predictive for reocclusion at follow-up (P = 0.001). In the streptokinase assigned patients (149) the infarct-related vessel was patent at follow-up angiography after a mean of 22 days in 66% of the patients with a mean residual diameter stenosis of 77 +/- 20%. CONCLUSION: Primary coronary angioplasty is a highly effective and safe reperfusion modality for patients with acute myocardial infarction. However, TIMI grade 2 flow through the infarct-related vessel immediately after angioplasty is a predictor of reocclusion.

Adult↗
PubMed1995

Comparison between regional myocardial perfusion reserve and coronary flow reserve in the canine heart.

Diameter stenosis and flow reserve are indices of morphological and functional severity of coronary artery stenosis. Flow reserve can be determined at coronary arterial or at myocardial level. In the presence of functional collateral circulation, coronary flow reserve and myocardial perfusion reserve may differ. We studied coronary flow, coronary flow reserve and myocardial perfusion reserve in an open chest dog model with intact collateral circulation, before and after induction of coronary artery stenosis. Coronary flow was determined with perivascular ultrasonic flow probes and myocardial perfusion reserve from digital angiographic images, in the stenotic as well as the adjacent non-stenotic coronary arteries. Before induction of a stenosis, a significant correlation existed between coronary flow reserve and myocardial perfusion reserve of the left anterior descending (r = 0.59; P < 0.005) and the left circumflex arteries (r = 0.84, P < 0.005). In stenotic arteries, coronary flow reserve and myocardial perfusion reserve decreased significantly (P < 0.005), but in the adjacent non-stenotic arteries coronary flow reserve was not affected. Myocardial perfusion reserve in the non-stenotic adjacent left anterior descending artery decreased significantly (P < 0.05) and no correlation was found between coronary flow reserve and myocardial perfusion reserve, whereas in the adjacent non-stenotic left circumflex artery there was no statistically significant decrease (4.1 +/- 1.6 --> 3.5 +/- 1.4) but there was a good correlation between coronary flow reserve and myocardial perfusion reserve (r = 0.85; P < 0.005). This study demonstrates that, in the presence of a stenosis and functioning collateral circulation, coronary flow reserve is not a reliable predictor of myocardial perfusion reserve; both parameters provide mutually complementary information.

Angiography, Digital Subtraction↗
PubMed1995

Automated and accurate assessment of the distribution, magnitude, and direction of pincushion distortion in angiographic images.

RATIONALE AND OBJECTIVES: Pincushion distortion continues to be a potential problem for the accurate assessment of arterial and catheter dimensions from x-ray angiograms. The authors investigate whether the distortion of state-of-the-art intensifiers is yet small enough to be neglected, and whether the rotation/angulation of the x-ray system plays a significant role. METHODS: The location and degree of distortion from x-ray images of a centimeter grid, which is positioned against the input screen of the image intensifier, are assessed automatically using image processing techniques. A value for the maximum amount of change in the distortion vector field is derived that allows the estimation of the maximum relative error associated with a diameter measurement uncorrected for pincushion distortion. RESULTS: The accuracy of the algorithm itself was assessed by rotating and translating the centimeter grid under the image intensifier at anteroposterior position. For the distortion vector length, the standard deviation in the measurement of the distortion areas was found to be 3.7 cm2 (1.3% of the total area). For the gradient values, the standard deviation was 2.2 cm2 or 0.75% of the total image intensifier area. In the second evaluation study, the centimeter grid was fixed onto the input screen of the image intensifier, and the gantry was rotated to span all possible positions of the system. In this case, the changes in measured areas were often much larger (up to 51.25 cm2 for a 9-inch image intensifier, equivalent to 15.6% of the total image intensifier area) than the standard deviations that had been found in the first evaluation study. CONCLUSIONS: The distortion is highly dependent upon the actual spatial position of the image intensifier, and correcting for pincushion distortion may therefore introduce larger errors than leaving the measurements uncorrected.

Algorithms↗
PubMed1995

Quantitative analysis of computed tomography scans of the lungs for the diagnosis of pulmonary emphysema. A validation study of a semiautomated contour detection technique.

RATIONALE AND OBJECTIVES: To develop an analytic software package based on automated contour detection for the objective and reproducible assessment of emphysema from computed tomography (CT) scans. METHODS: A semiautomated technique was developed for the definition of lung contours in CT cross-sections followed by the assessment of pulmonary CT parameters describing the disease state. For 78 images, the semiautomated contour detection was performed and compared with contours drawn by an experienced radiologist by calculating the systematic area difference (bias) and differences in pulmonary CT parameters such as the mean lung density (MLD). In addition, intraobserver and interobserver variabilities were determined in a subset of 15 images. RESULTS: The areas enclosed by the semiautomatically detected contours were slightly larger than the manual ones (bias < 2.1%). The biases in the observer studies were smaller in the semiautomated versus the manual case (0.3% vs. 1.3%). The standard deviation of the MLD differences with a manual analysis was larger by a factor of five than in the semiautomated case. On average, manual analysis required 2 minutes, 18 seconds per lung; this time was reduced to 11.5 to 29 seconds with the semiautomated approach, depending on the respiration state. CONCLUSIONS: The semiautomated approach is preferred over the manual approach because of its higher consistency and its shorter analysis time.

Adult↗
PubMed1994

Catheter sizes for quantitative coronary arteriography.

In quantitative coronary arteriography (QCA), the outer diameter of the contrast catheter is used almost exclusively as the calibration device. Since the true outer diameter of these catheters are smaller than the French sizes listed by the manufacturer, it has been advocated to measure the actual sizes with a precision micrometer. However, this represents a significant effort in the organizations of the QCA Angiographic Core Laboratories and of the participating cardiac catheterization laboratories. In the Dutch REGRESS trial on regression/progression of coronary artery disease, we have measured a total of 2,104 catheters from four different manufacturers. In 2,048 of the 2,104 catheters the variabilities in the measurements were 0.02-0.03 mm, which represents an error of only 1% of the average catheter sizes. In the remaining 56 catheter measurements, the variability was 0.04 mm. From these data we may conclude that from now on the stated mean values can be used for calibration purposes. This has important practical consequences for running clinical trials and QCA Core Laboratory operations.

Calibration↗
PubMed1994

Postmortem validation of the automated coronary analysis (ACA) software package.

Goal of this study was to compare the quantitative coronary arteriographic (QCA) results obtained with the Philips DCI/ACA analytical software package with those from postmortem casts in an animal experimental setting. Standard digital coronary arteriograms were obtained from 6 mongrel dogs. After the imaging procedure, the dogs were sacrificed and casts were made of the coronary trees by filling the vessels with a mixture of radio-opaque barium and silicone gel at a fixed pressure of 100 mmHg. Vessel diameters were measured from the digital arteriograms at a total of 118 selected locations with the ACA package. Thin slices were cut from the casts at these same measurement locations and the areas of the cross sections were obtained by manual tracing of the outline of each slice in an approximately 40 x magnified image. From these cross-sectional areas, cast diameters were derived using the formula for circular cross-sections. Cast diameters ranged in size from 0.69 to 3.30 mm. The systematic error between the measurements was found to be 0.058 mm; (p < 0.015) and the standard deviation of the signed difference 0.255 mm; the correlation coefficient was r = 0.91. The largest error sources are supposed to be the slight differences in the selection of identical positions in the X-ray images and on the casts, and the 'out-of-plane' magnification for a number of vessel locations. This postmortem study demonstrates that the diameters of coronary vessels can be measured from digital arteriograms with the DCI/ACA package with a high degree of accuracy and precision.

Animals↗