Gerhard Koning

Comparison of accuracy and precision of quantitative coronary arterial analysis between cinefilm and digital systems

In this chapter we have compared the accuracy and precision of two state-of-the-art analytical software packages for quantitative coronary arteriography (QCA) developed in our laboratory. The two packages are the QCA package (Versions 1.11 and 1.2) on the film-based Cardiovascular Measurement System (CMS), and the ACA package (Version 1.0) on the Philips Digital Cardiac Imaging System (DCI). In these studies the accuracy is defined as the systematic error described in terms of the mean signed difference between actual and measured values of phantoms or catheters, or between the values from repeated measurements; ideally the systematic errors should be as small as possible. The precision or random error is described in terms of the standard deviation of these signed differences; ideally these random errors should be as small as possible as well. In this chapter four comparative studies have been described.

State of the Art in Quantitative Coronary Arteriography as of 1996

In this chapter the important developments which have led to the third generation in quantitative coronary arteriographic (QCA) analytical software are presented, as well as current developments in the fields of image compression and storage. The conventional QCA approaches with automated contour detection techniques based on Minimum Cost contour detection Algorithms (MCA) have been well established and validated. However, further improvements in the calculations of the diameter and reference diameter functions were needed, especially for complex morphology and for stent applications. The development of the Gradient Field Transform (GFTR) approach for the quantitation of complex lesions represents a major step forward in QCA. With the advent of the cineless catheterization laboratory, the issue of image compression has become of major relevance. Phantom studies with lossy JPEG image compression at 5122 matrix size demonstrate that the compression factor (CF) should not exceed the level of 10. On the other hand, if JPEG and LOT lossy compression schemes (CF’s of 5,8 and 12) are applied to routinely acquired coronary angiographic image results, QCA measurements demonstrate that all three compression factors lead to significantly increased random differences in the measurements. These results suggest that even the JPEG and LOT compression ratio of 5 is not acceptable for QCA. Finally, an extensive QCA study has demonstrated that S-VHS video tape is unacceptable for QCA and should be excluded from quantitative angiographic clinical trials.

Quantitative coronary ultrasound: state of the art

Intravascular Ultrasound (IVUS) provides real-time high resolution images of the arterial wall. By performing a three-dimensional reconstruction, it permits an advanced assessment of the vessel, lumen and wall morphology. Recently, the straight stacking of the IVUS images has been extended by a geometrically correct orientation of the images in 3D space, using biplane angiographic images. Quantification of IVUS images, both in 2D and 3D, requires segmentation of the images. Automated segmentation of IVUS images for quantitative analysis reduces the required time and the subjectivity of boundary tracing. Different segmentation approaches for 2D and 3D IVUS are discussed, including the commercially available packages for analysis of IVUS images. Furthermore different approaches for the 3D reconstruction including the use of biplane angiographic images are discussed. This chapters finishes with a discussion about the future directions of IVUS including the developments in the area of RF-data analysis and the developments of new devices.

Issues in the performance of quantitative coronary angiography in clinical research trials

Quantitative coronary analysis remains the classical and most commonly used tool to assess the results of coronary pharmacological or mechanical intervention. The authors review the methodology of this type of analysis, highlighting the pros and cons of previous recommendations. Special interest has been devoted to catheter calibration and the choice of angiographic views for optimal measurement and reliability. Significant additional information in terms of acute gain, late loss or restenosis rate is not gained by the use of averaged orthogonal measurements as compared to the more simple single view approach. Also calibration procedures can be simplified by using tables of mean measured values for various types of catheters instead of measuring each catheter with a precision micrometer and by doing calibration measurements on contrast filled instead of flushed catheters. Moreover, specific in vitro and in vivo criteria have been proposed and tested for acceptance of catheter type and size in QCA analyses. Based on these criteria only catheters of sufficient size (6F or greater) and approved for QCA are recommended.

Angiographic core laboratory analyses of arterial phantom images: Comparative evaluations of accuracy and precision

Quantitative coronary arteriography (QCA) is commonly regarded as a reproducible and accurate method of assessing coronary anatomy. Centralized, quantitative core laboratory analysis of clinical study images has consequently become the standard for determining interval change in coronary anatomy. QCA systems and laboratory methods, however, are known to vary among core facilities and the effect of such differences on the variability of quantitative assessments among angiographic core laboratories (ACL) has not been studied. We evaluated QCA variability among seven active ACL, using four differing QCA systems by comparing analyses performed on a common set of phantom cinefilm images. Phantom analyses were performed in an automated, un-edited fashion on images of a plexiglass arterial phantom containing eleven precision drilled lumens (0.68-5.06 mm). Phantom images were acquired under varying radiographic conditions (5″ and 7″ image intensifier magnifications at 70 and 90 kV with uniform (scatter medium) and non-uniform (patient anatomy) backgrounds). Over the range of phantom diameters, analysis differences from actual luminal dimensions ranged widely (+ 0.42 to −0.45 mm) among ACL.

Current and future developments in QCA and image fusion with IVUS

Although quantitative coronary arteriography (QCA) has been around now for quite some time, research and development continue to take place along several directions. First of all, the imaging medium has changed from the traditional 35 mm analog cinefilm to the digital world with the CD-R as the preferred carrier. This required adaptations of the basic contour detection algorithms. Stimulated by these same changes, digital review stations or DICOM-Viewers have been developed. In addition, third-generation QCA algorithms have been designed and implemented, and applied to quantitate complex morphology and radiopaque stents.

Quantitative Cardiovascular Image Analysis: Current Status and what are Realistic Expectations for the Future?

Cardiology is typically an image oriented specialty. Single still images, but much more so dynamic and increasingly three-dimensional image sequences, play a major role in clinical decision making and clinical research trials. Of major interest is always the state of the coronary arteries and of the left ventricular function. In this chapter an overview is given of the various quantitative approaches using automated edge detection techniques which have been developed in our departments to: 1) assess the severity of disease of coronary obstructions from x-ray arteriography and intravascular ultrasound; and 2) assess the global and regional left ventricular function from x-ray angiography, echocardiography and magnetic resonance (MR) imaging. Also, the possibilities of MR flow velocity mapping are presented. In addition, for each modality and application a short description is given of the future developments and expectations. Finally, it is recognized that the automated combination of the data from the different imaging modalities (i.e. image fusion) will be a topic of major research in the future. As a current and practical example, the image fusion of biplane x-ray arteriography and 3D intravascular ultrasound is discussed.