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Letters to the Editor |
,
Frank Roemer, MD, and
Harry Genant, MD
Department of Diagnostic Radiology, Uniklinikum Schleswig-Holstein, Campus Kiel Arnold-Heller-Strasse 9, Kiel, 24105 Schleswig-Holstein, Germany*
Department of Radiology, University of California, San Francisco e-mail: mohr-a@arcor.de
Editor:
With interest we read the article of Dr Langheinrich and colleagues in the June 2004 issue of Radiology (1). The authors present an interesting new approach for the analysis of atherosclerosis with the use of micro–computed tomography (CT). This method allows for two- and three-dimensional imaging and quantitative analysis. Gray-scale evaluation was used to classify lesions as fibrous, atheromatous, calcified, or lipid-rich. The results of this study are strongly supported by our own experiences with micro-CT, but there are some issues that need to be discussed.
The authors state that micro-CT does not produce artifacts that interfere with image analysis. However, figure 1a clearly shows artifacts around the calcified lesions and a central circular structure. The first may be due to beam hardening, the latter to a detector problem. Both cause attenuation differences, however, and should affect the results if these areas are included in the gray-scale analysis.
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Another advantage of micro-CT is its suitability for experimental vascular stent placement. In contrast to other methods, which can be affected by enormous artifacts (such as at magnetic resonance imaging or ultrasonography) or problems with sample preparation (such as at histologic examination), micro-CT is capable of sufficient imaging. Our experiences demonstrate that it is possible to image postinterventional calcified plaque fractures (Figure).
REFERENCES
Departments of Radiology* and Pathology, Justus-Liebig University of Giessen Klinikstrasse 36, 35385 Giessen, Germany e-mail: alexander.langheinrich@radiol.med.uni-giessen.de
We are grateful for the thoughtful and constructive comments of Dr Mohr and colleagues with regard to our article (1). We are happy that our results are strongly supported by Dr Mohr and colleagues.
The major issue raised appears to be the well-known ring and beam-hardening artifacts. These artifacts did not affect quantitative analysis of vessel wall parameters in our study, such as plaque area, lumen area, media area, vessel wall perimeter, and calcified area. Measurements of relative gray-scale attenuation differences of plaque composition were performed on images without visible and detectable artifacts, as demonstrated in figures 2 and 3 (1).
Extraction of histologic images is a laboratory- and time-consuming job. Up to now, serial sectioning has been difficult because of technical loss of slides (ie, convolving of adjacent slices), compression, or translational displacement. In our opinion, micro-CT offers a more easy and precise generation of a complete three-dimensional data set compared with conventional histologic examination.
First results of evaluation of in-stent restenosis parameters have been published recently (2). In this study, we demonstrated the technical feasibility of micro-CT in the quantification of in-stent restenosis parameters. Because of metal artifacts, we developed perfusion techniques to allow visualization and quantification of vessel wall parameters.
REFERENCES
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