HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH RSS TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) All Versions of this Article: jnumed.108.051920v1 49/7/1107    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JNM Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hautzel, H. Articles by Müller, H.-W. Search for Related Content PubMed PubMed Citation Articles by Hautzel, H. Articles by Müller, H.-W.

Assessment of Large-Vessel Involvement in Giant Cell Arteritis with ¹⁸F-FDG PET: Introducing an ROC-Analysis–Based Cutoff Ratio

¹ Department of Nuclear Medicine, Heinrich-Heine-University of Düsseldorf, Düsseldorf, Germany; ² Department of Nuclear Medicine (KME), Research Centre Jülich, Jülich, Germany; and ³ Department of Endocrinology, Diabetology and Rheumatology, Heinrich-Heine-University of Düsseldorf, Düsseldorf, Germany

Correspondence: For correspondence or reprints contact: Hubertus Hautzel, Department of Nuclear Medicine (KME), Research Centre Jülich, Leo-Brandt-Strasse, D-52428 Jülich, Germany. E-mail: h.hautzel{at}fz-juelich.de

In the diagnosis of giant cell arteritis (GCA) with aortic involvement, ¹⁸F-FDG PET has been demonstrated to be a powerful tool. No other imaging method is able to directly detect acute inflammation within the aortic wall. However, because GCA is a rare PET indication, the assessment of GCA with ¹⁸F-FDG PET remains difficult and highly dependent on the experience of the investigator. This study aimed to semiquantify the relationship between aortic and liver uptake and to introduce a receiver operating characteristic (ROC)–based cutoff ratio to allow investigator- and experience-independent GCA diagnosis with optimal sensitivity and specificity. Ratios of aortic wall uptake versus liver uptake were calculated in a group of GCA patients and a control group. These data were assessed in an ROC analysis, and finally, a cutoff-ratio–optimizing strategy was applied. Methods: Twenty-three patients with initially suspected GCA (18 positive for GCA criteria, 5 negative) and 36 matched controls were included. The control subjects underwent PET for oncologic diagnostics. None had intrathoracic or hepatic disease or therapy-related tracer accumulation. Additionally, physiologic liver metabolism was ensured by the presence of normal liver enzymes. After defining regions of interest over the thoracic aorta and the liver, we calculated maximal standardized uptake value ratios. Sensitivities and specificities for cutoff ratios from 0.1 to 2.5 were estimated and were ultimately used to assess an optimal cutoff ratio for separating GCA patients from controls. To further investigate the usefulness of the resulting cutoff ratio, we tested it in a second control group with changed hepatic metabolism and elevated liver enzymes. Results: ROC analysis revealed optimal selectivity for a cutoff ratio of 1.0. This ratio led to a sensitivity of 88.9%, a specificity of 95.1%, and an accuracy of 94.4%. When this aorta-to-liver ratio was applied to the control group with pathologic liver metabolism, the resulting specificity was 95.6%. Conclusion: The ¹⁸F-FDG PET region-of-interest analysis with aorta-to-liver maximal standardized uptake value ratios is a reliable, investigator-independent indicator of GCA not affected by minor inflammation-associated changes in hepatic metabolism. Our results for a cutoff ratio of 1.0 prove that ¹⁸F-FDG PET is a method of high sensitivity and specificity for GCA-related large-vessel inflammation.

Key Words: giant cell arteritis • FDG • PET • ROC analysis • inflammation

COPYRIGHT © 2008 by the Society of Nuclear Medicine, Inc.

Related articles in JNM:

This Month in JNM

JNM 2008 49: 13A-14A. [Full Text]