Ad den Boer

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.

Geometric Vascular Remodeling After Balloon Angioplasty and β-Radiation Therapy: A Three-Dimensional Intravascular Ultrasound Study

BACKGROUND Endovascular radiation appears to inhibit intimal thickening after overstretching balloon injury in animal models. The effect of brachytherapy on vascular remodeling is unknown. The aim of the study was to determine the evolution of coronary vessel dimensions after intracoronary irradiation after successful balloon angioplasty in humans. METHODS AND RESULTS Twenty-one consecutive patients treated with balloon angioplasty and beta-radiation according to the Beta Energy Restenosis Trial-1.5 were included in the study. Volumetric assessment of the irradiated segment and both edges was performed after brachytherapy and at 6-month follow-up. Intravascular ultrasound images were acquired by means of ECG-triggered pullback, and 3-D reconstruction was performed by automated edge detection, allowing the calculation of lumen, plaque, and external elastic membrane (EEM) volumes. In the irradiated segments, mean EEM and plaque volumes increased significantly (451+/-128 to 490.9+/-159 mm(3) and 201.2+/-59 to 241.7+/-74 mm(3); P=0.01 and P=0.001, respectively), whereas luminal volume remained unchanged (250.8+/-91 to 249.2+/-102 mm(3); P=NS). The edges demonstrated an increase in mean plaque volume (26.8+/-12 to 32. 6+/-10 mm(3), P=0.0001) and no net change in mean EEM volume (71. 4+/-24 to 70.9+/-24 mm(3), P=NS), resulting in a decrease in mean luminal volume (44.6+/-16 to 38.3+/-16 mm(3), P=0.01). CONCLUSIONS A different pattern of remodeling is observed in coronary segments treated with beta-radiation after successful balloon angioplasty. In the irradiated segments, the adaptive increase of EEM volume appears to be the major contributor to the luminal volume at follow-up. Conversely, both edges showed an increase in plaque volume without a net change in EEM volume.

Edge detection versus densitometry in the quantitative assessment of stenosis phantoms: An in vivo comparison in porcine coronary arteries

The aim of this study was the in vivo validation and comparison of the geometric and densitometric technique of a computer-assisted automatic quantitative angiographic system (CAAS system). In six Landrace Yorkshire pigs (45 to 55 kg), precision-drilled phantoms with a circular lumen of 0.5, 0.7, 1.0, 1.4, and 1.9 mm were percutaneously introduced into the left anterior descending or left circumflex coronary artery. Twenty-eight coronary angiograms obtained with the phantom in a wedged intracoronary position could be quantitatively analyzed. Minimal lumen diameter, minimal cross-sectional area, percent diameter stenosis, and cross-sectional area stenosis were automatically measured with both the geometric and densitometric technique and were compared with the known phantom dimensions. When minimal lumen diameter was measured using the geometric approach, a nonsignificant underestimation of the phantom size was observed, with a mean difference of -0.06 +/- 0.14 mm. The larger mean difference observed with videodensitometry (-0.11 +/- 0.20 mm) was the result of the failure of the technique to differentiate the low lumen videodensities of two phantoms of smaller size (0.5 and 0.7 mm) from a dense background. Percent cross-sectional area stenosis measured with the two techniques showed a good correlation with the corresponding phantom measurements (mean difference between percent cross-sectional area stenosis calculated from the quantitative angiographic measurements and the corresponding phantom dimensions was equal to 2 +/- 6% for both techniques, correlation coefficient = 0.93 with both techniques, SEE = 5% with the geometric technique and 6% with the densitometric approach).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary arteriography for quantitative analysis: experimental and clinical comparison of cinefilm and video recordings.

Although use of videotape for the recording of coronary angiograms continues to grow, the validity of quantitative coronary angiographic analysis of video images remains unknown. To estimate the reliability of angiographic images recorded on videotape, experimental and clinical angiograms were recorded simultaneously on both 35 mm cinefilm and super-VHS videotape with normal images and with spatial filtering of the images (edge enhancement) on a digital cardiac imaging system. The experimental angiographic studies were performed with plexiglass blocks and stenosis phantom of 0.5 to 3.0 mm in diameter. The clinical angiograms were recorded in 20 patients undergoing percutaneous transluminal coronary angioplasty (31 frames before and 20 frames after percutaneous transluminal coronary angioplasty). The cinefilm and corresponding videotapes were analyzed off-line with the new version of the coronary angiography analysis system. For the experimental study, measurements of minimal luminal diameter obtained from cinefilm, normal-image videotape, and edge-enhanced videotape were compared with the true phantom diameter. In the clinical study the agreement between measurements obtained from cinefilm and measurements from normal-image videotape and edge-enhanced videotape was examined. In the phantom series the accuracy and precision of quantitative coronary angiography measurement for cinefilm were -0.10 +/- 0.08 mm, for normal-image videotape -0.11 +/- 0.18 mm, and for edge-enhanced videotape -0.10 +/- 0.11 mm (mean +/- SD). In the clinical series, the differences between measurements from cinefilm and normal-image videotape were 0.14 +/- 0.20 mm and from cinefilm and edge-enhanced videotape 0.04 +/- 0.13 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of brachytherapy strategies based on dose-volume histograms derived from quantitative intravascular ultrasound.

PURPOSE We present in this paper the comparison, by simulation, of different treatment strategies based either on beta- or gamma-sources, both with and without a centering device. Ionizing radiation to prevent restenosis is an emerging modality in interventional cardiology. Numerous clinical studies are presently being performed or planned, but there is variability in dose prescription, and both gamma- and beta-emitters are used, leading to a wide range of possible dose distributions over the arterial vessel wall. This paper discusses the potential merits of dose-volume histograms (DVH) based on three-dimensional (3-D) reconstruction of electrocardiogram (ECG)-gated intravascular ultrasound (IVUS) to compare brachytherapy treatment strategies. MATERIALS AND METHODS DVH describe the cumulative distribution of dose over three specific volumes: (1) at the level of the luminal surface, a volume was defined with a thickness of 0.1 mm from the automatically detected contour of the highly echogenic blood-vessel interface; (2) at the level of the IVUS echogenic media-adventitia interface (external elastic lamina [EEL]), an adventitial volume was computed considering a 0.5-mm thickness from EEL; and (3) the volume encompassed between the luminal surface and the EEL (plaque + media). The IVUS data used were recorded in 23 of 31 patients during the Beta Energy Restenosis Trial (BERT) conducted in our institution. RESULTS On average, the minimal dose in 90% of the adventitial volume was 37 +/- 16% of the prescribed dose; the minimal dose in 90% of the plaque + media volume was 58 +/- 24% and of the luminal surface volume was 67 +/- 31%. The minimal dose in the 10% most exposed luminal surface volume was 296 +/- 42%. Simulations of the use of a gamma-emitter and/or a radioactive source train centered in the lumen are reported, with a comparison of the homogeneity of the dose distribution. CONCLUSIONS It is possible to derive DVH from IVUS, to evaluate the dose delivered to different parts of the coronary wall. This process should improve our understanding of the mechanisms of action of brachytherapy.

Videodensitometry in percutaneous coronary interventions: a critical appraisal of its contributions and limitations

The rapid development of percutaneous coronary revascularization techniques, such as balloon angioplasty, atherectomy and stenting, has created new demands for quantitative angiography. These include the need for reducing the time dedicated to quantitative analysis during interventional procedures, as well as obtaining reliable measurements in unfavorable conditions, such as in vascular segments with complex luminal morphology resulting from percutaneous intervention [1–5]. The role that videodensitometry may play in the solution of these problems has barely been explored and is still unclear, although from a theoretical point of view it may offer at least two major potential contributions [6]. Firstly, when videodensitometry is used measurements can be performed from any angiographic projection, facilitating data collection and avoiding cumbersome and time-consuming analysis in orthogonal angiographic projections. Secondly, since luminal cross sectional area is calculated directly from the densitometric profile, no assumptions on luminal morphology are required, a fact that may contribute to a more realistic appraisal of the result of the intervention. The reliability of these appealing features in clinical practice, although supported by the theoretical background of the technique and by experimental work, is still controversial [7–15].

Does coronary lumen morphology influence vessel cross-sectional area estimation? An in vitro comparison of intravascular ultrasound and quantitative coronary angiography

Over the last 10 years quantitative coronary angiography has clearly emerged as the gold standard coronary imaging modality. However, despite the objectivity and reproducibility of coronary luminal measurements provided by quantitative angiographic analysis systems, a number of important limitations have been identified through their application to interventional procedures [1]. In particular, complex coronary lesions (for example, thrombus containing or ulcerated lesions) or the modifications in luminal geometry caused by percutaneous interventions, may yield inaccurate and unreliable luminal measurements [1–6]. These pitfalls of quantitative coronary angiography have been highlighted in recent years through the emergent clinical application of intracoronary ultrasound and angioscopy. Intravascular ultrasound imaging itself continues to undergo rapid evolution and has been advanced by its proponents as having a superior capacity for demonstrating luminal morphology, especially after coronary interventions [7–9].

Quantitative Digital Angiographic Techniques

There is an increasing demand for the objective and reproducible assessment of coronary arterial dimensions and for the functional significance of coronary obstructions to study the efficacy of new recanalization techniques in the catheterization laboratory, to evaluate new approaches to achieve regression or no-growth of coronary atherosclerosis and also as a means for diagnostic and therapeutic decision making during the cardiac catheterization procedure. This last application requires the use of digital cardiac imaging systems with the capability to store the images online on real-time disks; at the present time, the other applications are usually evaluated off-line from 35mm cinefilm.