Acoustic shadowing impairs accurate characterization of XXXX in carotid ultrasound examinations.

@entity1 @entity75 @entity601 @entity2270 @entity850 @entity543
OBJECTIVE: Duplex ultrasonography (DUS) has been the mainstay for diagnosing @entity543 and is often the sole diagnostic modality used prior to intervention. Highly calcified plaque, however, results in an acoustic shadow (AcS) that obscures the vessel lumen and inhibits the sonographer's ability to obtain Doppler velocity measurements. It is unknown whether DUS can accurately determine the degree of @entity543 in these settings. METHODS: From July 2012 to December 2013, all @entity1 with AcS on DUS measuring >= 5  mm in the @entity2270 were cross-referenced with multidetector computed tomographic angiography ( @entity601 -CTA) images of the neck to define the study population. After standardizing the @entity601 -CTA windows, percent @entity850 was determined by cross-sectional area reduction using two separate previously described methods based on North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trial (ECST) criteria. DUS waveform parameters in the internal carotid artery near the AcS were then compared with these @entity601 -CTA measurements to determine the accuracy of DUS in characterizing the severity of @entity543 . RESULTS: During this period, 8517 DUS studies were performed at the Massachusetts General Hospital, 550 of which had AcS, for an incidence of 6.45%. There were 92 lesions with a concomitant @entity601 -CTA; however, seven were excluded because of poor study quality, because >= 6  months had elapsed between DUS and @entity601 -CTA, or because the @entity1 had undergone carotid reconstruction between studies. Of the 85 remaining lesions, DUS characterized 17 as severe (peak systolic velocity [PSV] >250  cm/s), 31 as moderate (PSV  = 151-250  cm/s), and 37 as mild (PSV  <=150  cm/s) stenoses using PSV criteria. PSV weakly correlated with CTA-NASCET (r  = 0.361; P  = .004) and CTA-ECST (r  = 0.306; P  = .004) percent @entity850 . Using PSV >250  cm/s as the predictor of >70% @entity850 , and a >= 70% cutoff by both CTA-ECST and CTA-NASCET methods as the reference measure, DUS sensitivity ranged from 22.7% to 32.5%, specificity from 89.4% to 91.1%, positive predictive value from 88.2% to 76.4%, and negative predictive value from 25% to 60.2%. A subgroup analysis of lesions identified as non-severe by DUS revealed that waveforms with lower deceleration were associated with severe @entity850 on CTA. CONCLUSIONS: In the presence of AcS, DUS alone is inadequate to accurately determine the degree of @entity543 with sensitivity, specificity, and negative predictive values far below that needed for clinical decision-making. @entity601 -CTA may be necessary for improved characterization of plaque in these @entity75 . Further studies are needed to determine DUS parameters that may identify @entity1 who should undergo further evaluation with @entity601 -CTA to characterize the true severity of the @entity850 .
