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Quantitative validation of a threshold for distinguishing free-floating ICA thrombus thrombus from complex plaque. Lum, Cheemun . · Iancu D. · Torres C, Thornhill, R. · Dowlatshahi, D. · Ottawa Stroke Research Group Neuroradiology Section The Ottawa Hospital, University of Ottawa,
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Quantitative validation of a threshold for distinguishing free-floating ICA thrombus thrombus from complex plaque Lum, Cheemun.·Iancu D.·Torres C, Thornhill, R.·Dowlatshahi, D.· Ottawa Stroke Research GroupNeuroradiology Section The Ottawa Hospital, University of Ottawa, Ottawa Hospital Research Institute
Background • Rounded filling defects at ICA origin=“doughnut sign” Patient 2 Patient 1
Background • > 90 % of patients with thrombus at ICA develop neurologic sequelae; hence prompt diagnosis is necessary 3
Background • Which filling defects are thrombus (FFT) vs plaque? Patient 2
Background • Resolution of filling defect with treatment using heparin/antiplatelet Pre-Rx Post-Rx ~ 1 wk
No resolution after medical therapy Patient 1 Diagnosis: complex plaque
Background • Luminal filling defects at the ICA origin imaged in the workup of stroke/TIA may be ulcerated plaque or free-floating thrombus (FFT) • Accurate identification critical potential distal embolization • paucity of imaging literature on FFT and its evolution, mostly single case reports • Controversy exists acute management: urgent endarterectomy versus medication • we treat possible FFT with antiplatelets or anticoagulation and perform imaging to evaluate evolution
Purpose • Filling defects identified at the ICA origin for the work-up of stroke/TIA may be due to an ulcerated plaque or free-floating thrombus (FFT). • Accurate identification of FFT is of critical importance because of the potential for distal embolization. • Prior research has suggested that the cranial-caudal extent of the filling defect seen at CT angiography (CTA) suggests a diagnosis of FFT rather than plaque. • The purpose of our study was to validate a previously described quantitative measurement for distinguishing FFT from complex plaque in the ICA.
Materials & Methods • Our PACS archive between February 2013 and July 2014 was searched retrospectively for reports with the key words "free floating" thrombus in the ICA. • Follow-up imaging reports were reviewed. Patients without follow-up imaging were excluded. • The cranial-caudal length of the filling defect was measured by an experienced neuroradiologist.
Materials & Methods • Filling defects which resolved completely or near completely on follow-up imaging were defined as FFT. • Filling defects which remained static on follow-up imaging were classified as complex plaque. • Patient demographics, imaging features and clinical data were collected and analyzed using univariate statistics. • We evaluated the diagnostic performance of a 3.8 mm thresholdfor diagnosing FFT.
Results • There were 22 patients identified as possible FFT of which three were excluded for lack of imaging follow up leaving 19 patients for analysis. • There were 16 males (84%) and three females (16%) with a mean age of 65 years.
Results • Median follow-up imaging was performed at 6 days. Mean length of filling defect was 9.3 versus 4.9 mm (p=0.43) in patients with FFT versus plaque. • A threshold of 3.8 mm had the following diagnostic test characteristics: • Sensitivity = 82.35% (CI: 56.55% - 95.99%)) • Specificity = 50.00% (CI: 8.17% to 91.83%) • Positive Predictive Value = 93.33% (CI: 67.98% to 98.89%) • Negative Predictive Value = 25.00% (CI: 4.12% to 79.66%)
Conclusions • Suspected cases of FFT seen at imaging with a threshold of 3.8 mm length had a high positive predictive value in this validationcohort. • Filling defects shorter than 3.8 mm may still represent FFT; however, the clinical consequences of these smaller thrombi are unclear. • A prospective study is warranted for further evaluation.
References • Menon BK, Singh J, Al-Khataami A, Demchuk AM, Goyal M,Calgary CTA Study Group (2010) The donut sign on CT angiography:an indicator of reversible intraluminal carotid thrombus? Neuroradiology 52(11):1055–1056, Epub 2010 Jul 13. • Jaberi A, Lum C, Stefanski P, Thornhill RE, Dowlatshahi D. Computed tomography angiography evaluation of internal carotid artery free-floating thrombus-single-center diagnosis, false-positives, and follow-up. Emerg Radiol. 2012 Mar 31. • Jaberi A, Lum C, Torres C, Iancu D, Thornhill R, Momoli F, Petrcich W, Dowlatshahi D. Computed Tomography Angiography Intraluminal Filling Defect is Predictive of Internal Carotid Free Floating Thrombus. Neuroradiology 2014 Jan;56(1):15-23. • Rebecca E. Thornhill, Cheemun Lum, Arash Jaberi, Pawel Stefanski, Carlos Torres, MD , Franco Momoli, William Petrcich, Dar Dowlatshahi. Can Shape analysis differentiate free-floating internal carotid artery thrombus from atherosclerotic plaque in patients evaluated with CTA for stroke or transient ischemic attack? Acad Radiol. 2014 Mar;21(3):345-54.