Cardiothoracic ratio in postmortem computed tomography: reliability and threshold for the diagnosis of cardiomegaly
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ORIGINAL ARTICLE
Cardiothoracic ratio in postmortem computed tomography: reliability and threshold for the diagnosis of cardiomegaly Sebastian Winklhofer • Nicole Berger • Thomas Ruder • Marina Elliott • Paul Stolzmann • Michael Thali • Hatem Alkadhi • Garyfalia Ampanozi
Accepted: 5 October 2013 / Published online: 31 October 2013 Ó Springer Science+Business Media New York 2013
Abstract The aim of this study was to evaluate the reliability of the cardiothoracic ratio (CTR) in postmortem computed tomography (PMCT) and to assess a CTR threshold for the diagnosis of cardiomegaly based on the weight of the heart at autopsy. PMCT data of 170 deceased human adults were retrospectively evaluated by two blinded radiologists. The CTR was measured on axial computed tomography images and the actual cardiac weight was weighed at autopsy. Inter-rater reliability, sensitivity, and specificity were calculated. Receiver operating characteristic curves were calculated to assess enlarged heart weight by CTR. The autopsy definition of cardiomegaly was based on normal values of the Zeek method (within a range of both, one or two SD) and the Smith method (within the given range). Intra-class correlation coefficients demonstrated excellent agreements (0.983) regarding CTR measurements. In 105/170 (62 %) cases the CTR in PMCT
S. Winklhofer N. Berger T. Ruder P. Stolzmann M. Thali G. Ampanozi Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, University of Zurich, Winterthurerstrasse 190/52, CH-8057 Zurich, Switzerland S. Winklhofer (&) N. Berger P. Stolzmann H. Alkadhi Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Raemistrasse 100, CH-8091 Zurich, Switzerland e-mail: [email protected] T. Ruder Institute of Diagnostic, Interventional, and Pediatric Radiology, University Hospital Bern, Freiburgstrasse, CH-3010 Bern, Switzerland M. Elliott Department of Archaeology, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
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was [0.5, indicating enlarged heart weight, according to clinical references. The mean heart weight measured in autopsy was 405 ± 105 g. As a result, 114/170 (67 %) cases were interpreted as having enlarged heart weights according to the normal values of Zeek within one SD, while 97/170 (57 %) were within two SD. 100/170 (59 %) were assessed as enlarged according to Smith’s normal values. The sensitivity/specificity of the 0.5 cut-off of the CTR for the diagnosis of enlarged heart weight was 78/71 % (Zeek one SD), 74/55 % (Zeek two SD), and 76/59 % (Smith), respectively. The discriminative power between normal heart weight and cardiomegaly was 79, 73, and 74 % for the Zeek (1SD/2SD) and Smith methods respectively. Changing the CTR threshold to 0.57 resulted in a minimum specificity of 95 % for all three definitions of cardiomegaly. With a CTR threshold of 0.57, cardiomegaly can be identified with a very high specificity. This may be useful if PMCT is used by forensic pathologists as a screening tool for medico
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