228 AJR:187, July 2006 AJR 2006; 187:228–234 0361–803X/06/1871–228 © American Roentgen Ray Society M E D I C A L I M A G I N G A C E N T U R Y O F Bitar et al. Identification of Complicated Atheroscler otic Plaque by MR Direct Thrombus Imaging Vascular Imaging • Original Research In Vivo Identification of Complicated Upper Thoracic Aorta and Arch Vessel Plaque by MR Direct Thrombus Imaging in Patients Investigated for Cerebrovascular Disease Richard Bitar 1,2 Alan R. Moody 1,2 General Leung 2 Alexander Kiss 3 David Gladstone 4 Demetrios J. Sahlas 4 Robert Maggisano 5 Bitar R, Moody AR, Leung G, et al. Keywords: cardiovascular imaging, hemorrhage, MR arteriography, MRI, peripheral vascular disease DOI:10.2214/AJR.05.1556 Richard Bitar is the recipient of a Canadian Heads of Academic Radiology (CHAR) resident grant and a Canadian Institutes of Health Research (CIHR) fellowship. Received September 1, 2005; accepted after revision October 25, 2005. 1 Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada. 2 Department of Medical Imaging, Sunnybrook Health Sciences Centre, 2075 Bayview Ave., AG46, Toronto, Ontario, Canada M4N 3M5. Address correspondence to A. R. Moody (alan.moody@sunnybrook.ca). 3 Institute for Clinical Evaluative Sciences (ICES), Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. 4 Department of Neurology and Regional Stroke Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. 5 Division of Vascular Surgery, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. OBJECTIVE. The objective of this article was to assess the feasibility of MR direct throm- bus imaging (MRDTI) to evaluate the prevalence and location of complicated upper thoracic aortic and arch vessel plaque in patients referred for evaluation of cerebrovascular disease. SUBJECTS AND METHODS. Patients referred for investigation of cerebrovascular disease by MRI were enrolled. Reasons for referral included transient ischemic attack/amau- rosis fugax, acute infarct, remote infarct, or asymptomatic carotid disease. Of the 348 patients initially scanned, 17 were excluded from the analysis. The final patient population included 331 patients (199 men, 132 women; mean age, 67.7 years). Patients were scanned using MRDTI, a 3D, T1-weighted, fat-suppressed spoiled gradient echo that exploits the T1 shortening effects of methemoglobin, directly visualizing hemorrhage/thrombus in the vessel wall, thus identify- ing complicated plaque. Complicated plaque was defined as a high signal within the athero- sclerotic plaque at least twice the signal intensity of muscle. RESULTS. Forty-three of 331 patients (13%) had complicated upper thoracic aortic ath- erosclerotic disease, arch vessel atherosclerotic disease, or both. The upper thoracic aorta was involved in 36 of 43 patients (83.7%), and the left subclavian artery was involved in 14 of 43 patients (32.6%). Both the right subclavian artery and the brachiocephalic artery were involved in one of 43 patients (2.3%). Complicated carotid plaque was seen in 25 of 43 patients (58.1%). CONCLUSION. MRDTI can be applied in the detection of complicated plaque in the up- per thoracic aorta and arch vessels. Complicated plaque was identified in 13% of the patient population. The upper thoracic aorta was the most common site involved. This technique could be useful for the screening of asymptomatic at-risk patients. therosclerosis is a systemic dis- ease that leads to raised plaques within the vessel wall of arteries such as the aorta, coronaries, and carotids [1]. Knowledge of a patient’s athero- sclerotic load is potentially clinically impor- tant. Atherosclerotic disease in the thoracic aorta has been linked to an increased risk of thromboembolic events (such as embolic stroke or ischemic bowel) and an increased risk of mortality and stroke [2, 3]. The Stroke Council and the Council on Clinical Cardiol- ogy of the American Heart Association (AHA)/American Stroke Association [4] have recommended that patients with cerebral ischemic symptoms have a comprehensive cardiovascular assessment. This statement underscores the need to investigate other vas- cular beds to account for the source of the symptoms experienced by a patient and to make a preoperative assessment of a patient’s potential morbidity and mortality. For exam- ple, knowledge of a patient’s atherosclerotic load may be important in coronary artery sur- gery because severe carotid artery and verte- bral artery stenosis can increase the perioper- ative risk of stroke [5]. Atherosclerotic plaques that lead to mor- bidity and mortality are usually modestly stenotic, often not seen by angiography [6]. The AHA has developed a classification sys- tem for atherosclerotic plaques [7], with intra- plaque hemorrhage and thrombosis as mark- ers that define atherosclerotic plaques as complicated (AHA type VIb/c) and at an in- creased risk of causing symptoms [7]. A study by Kolodgie et al. [8] confirmed the as- sociation in the coronary arteries between in- traplaque hemorrhage and plaque instability. As hemoglobin within intraplaque hemor- rhage matures, it goes through various states, one of which, methemoglobin, causes short- ening of T1 relaxation and results in the high signal intensity seen in T1-weighted imaging A Downloaded from www.ajronline.org by 52.73.204.196 on 05/16/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved