Evaluation of a Computed Tomography Coronary Angiography Scan - Advantages and Disadvantages of Different Post-processing Techniques

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Computed tomography coronary angiography (CTCA) is increasingly performed worldwide. For the interpretation of the acquired data set, different post-processing techniques are available, such as multiplanar reformation, maximum-intensity projections, direct volume rendering, virtual coronary angioscopy or the angiographic view. Each of these techniques shows certain advantages and disadvantages during application and image interpretation. Thus, a combination of post-processing techniques for the interpretation of CTCA studies should be used. When starting to perform and interpret CTCA, a systematic approach is mandatory for accurate diagnosis. We developed a practical algorithm in our institution for the interpretation of CTCA studies with special emphasis on interpretation steps to avoid a false-negative or false-positive diagnosis. In this article we discuss the strengths and weaknesses of the different post-processing techniques available for
evaluation of CTCA and provide a systematic approach for interpreting a CTCA study, with an emphasis on how to avoid false-positive and false-negative classifications.

Keywords Computed tomography, coronary angiography, coronary arteries, interpretation, post-processing techniques

Disclosure: The authors have no conflicts of interest to declare.
Received: 19 April 2010 Accepted: 12 August 2010 Citation: European Cardiology, 2010;6(4):10├óÔé¼ÔÇ£4
Correspondence: Sebastian Leschka, Institute of Radiology, General Hospital Saint Gall, Rorschacherstrasse 95, 9007 St Gallen, Switzerland. E: sebastian.leschka@kssg.ch


Computed tomography coronary angiography (CTCA) has entered the level of daily clinical practice in many institutions worldwide. All studies previously performed on the diagnostic accuracy of CTCA have shown a high negative predictive value, indicating a high ability of this method to exclude relevant coronary artery disease.1├óÔé¼ÔÇ£3 However, CTCA is highly demanding not just of the technology, but also of the interpreters of the CTCA data sets. For the inexperienced reader a relevant coronary lesion could be easily missed or a non-relevant stenosis could be overestimated as a significant lesion, particularly in the presence of severe calcified deposits. In addition, artefacts might be mistaken for real lesions, resulting in avoidable false-positive classifications. It is of utmost importance that a CTCA study is correctly interpreted as the reported high negative predictive value of CTCA is one of the main strengths of this method, and a patient with a negative scan result will frequently not undergo further cardiac diagnostics. On the other hand, any false-positive results at CTCA result in further invasive work-up, which would have been avoided if the CTCA interpretation had been correct.

With improvements in spatial resolution, CTCA data sets have become increasingly large with about 1,000├óÔé¼ÔÇ£5,000 images per examination. Therefore, simple transverse scanning of such data sets by interactively moving up and down a stack of axial slices is impractical and favours a shift towards volume imaging and 3D image display.4 Thus, the interpreter of a CTCA data set should be familiar with the advantages and disadvantages of the available post-processing techniques. Some of these post-processing techniques have a large number of possible parameters that may be tuned to obtain the best visualisation for a given data set. Interpretation of CTCA requires interactive manipulation and browsing of images. Therefore, the interpreter of CTCA can improve his or her reading by understanding the principles of the individual post-processing techniques and by learning to interact with his workstation.

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