Coronary Artery Imaging with Multidetector CT: Visualization Issues

Abstract

Noninvasive imaging of the coronary arteries has attracted growing interest in the past few years. One of the possible acquisition techniques is multidetector computed tomography (CT) that produces large three-dimensional (3D) data sets that require visualization techniques for data evaluation. The objective of this article is to increase knowledge of possible 3D visualization techniques together with their advantages and disadvantages for the routine evaluation of cardiac data sets. Common imaging techniques available to the radiologist at standard workstations are multiplanar reformation (MPR), oblique MPR, curved MPR, maximum-intensity projection (MIP), shaded-surface display, and direct volume rendering. Each of these techniques has its advantages and disadvantages for the visualization of the coronary artery tree. Several additions to the basic techniques have been developed to overcome some of their shortcomings. Different clinical examinations, such as stent evaluation, stenosis evaluation, and bypass evaluation, require different visualization techniques. The choice of preferred technique for each clinical study depends on the advantages and disadvantages of the various techniques as described in the literature. Because of the large number of possible settings and projection angles, it is important for users to interactively manipulate the images and review the whole vessel volume rather than just looking at static reformatted images. Errors such as findings of false stenoses can be avoided by means of accurate and appropriate use of software features. This requires training of users both with regard to the capabilities of the software and the background of the different techniques and their possible pitfalls. The authors believe that volume rendering of the whole heart is useful for anatomic evaluation of the coronary arteries. For more detailed observation of specific lesions, slab imaging with volume rendering or MIP is required.

Volume Rendering versus Maximum Intensity Projection in CT Angiography: What Works Best, When, and Why

“…The rendering technique is the computer algorithm used to transform serially acquired axial CT image data into 3D images. There are a number of different methods, but most can be divided into the following two classes: thresholding-or surface-based (binary) techniques; and percentage-or semitransparent volume-based (continuous) techniques (1)(2)(3). The initial selection of the rendering technique greatly affects the quality of the reconstructed images in any 3D application.…”

“…In the MIP algorithm, the highest-attenuation voxels along lines projected through the volume data set are selected (3). The subset of these high-attenuation voxels from the volume is then incorporated into a twodimensional image.…”

“…The capacity to depict soft tissue and vasculature at the same time makes volume rendering useful for tumor staging (35) (Fig 17). One of the challenges of volume rendering is that the user must adjust the display parameters (eg, degree of opacity) to most accurately depict the vasculature (3,36). Because volume rendering is an interactive process, it is vulnerable to interobserver variability (37) and dependent on user mastery in the optimization of rendering parameters.…”

Angiografia coronariana minimamente invasiva através de tomografia com múltiplos detectores

“…Since they are in close contact with the cardiac muscle they present intense motility. These characteristics make the minimally invasive coronary angiography a superlative endeavor, requiring imaging equipment with high spatial and temporal resolution 10 .…”

“…The most common methods include MPR (multiplanar reformation), oblique MPR, curved MPR, MIP (maximum-intensity projection), shaded-surface display and three-dimensional reconstruction (3-D). Considering the large number of settings and projection angles it is important that the images are manipulated so as to visualize the entire vessel volume, taking advantage of the features of each technique 10,11 (fi g.1, 2 and 3).…”