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Study Objectives: Carotid ultrasound using dedicated 3D systems is more reproducible and better quantifies disease compared to 2D Doppler ultrasound, but 3D system costs limit access Low-cost point-of-care 3D ultrasound (POC 3DUS) can augment any 2D ultrasound This system previously had near-perfect agreement for fetal measurements between novice and expert operators We hypothesized that carotid assessment would not differ between novice-acquired 3DUS interpreted by novices and experts and CT angiography (CTA) interpreted by radiologists Methods: We adhered to STARD criteria Enrollment was by prospective convenience sample at a single medical center;any patient with recent/upcoming head and neck CTA was eligible 2D B mode US acquisitions used a linear probe coupled to a screen capture device or smartphone, plus an orientation sensor and 3D reconstruction software Scans were displayed as 2D stacks and intersecting cardinal planes (Figure) 3DUS were interpreted by medical students (novice), US fellowship trained emergency physicians, and radiologists (expert) CTAs were interpreted by neuroradiologists Readers described NASCET stenosis, plaque, intimal-medial thickness, and minimum luminal cross-sectional area Inter-reader reliability was measured by intraclass correlation coefficient (ICC)/kappa We determined a sample size of 50 subjects for ICC 0 7 (alpha 0 05, power 0 8) and kappa 0 8 3DUS sensitivity/specificity/LRs were estimated with CTA as the reference standard Anonymous patient satisfaction surveys were administered Results: Due to COVID-19, enrollment ended after 30 subjects (144 3DUS, 33 CTAs) Of the 60 arteries imaged, 21 had plaque on clinical CTA interpretation Analysis is still in process Mean 3DUS acquisition and reconstruction times were 13 1 sec (median 12 7, IQR 9 1-17 3) and 7 9 sec (med 8 0, IQR 5 0-10 3) Mean 3DUS interpretation time was 3m, 52s (med 3:06, IQR 2:14-4:49) for the first 497 3DUS reads 13 patient surveys were completed Mean subject willingness to repeat 3DUS was 8 1/10 (med 10, IQR 6 1-10) 2 subjects reported increased discomfort during the exam (mean change 0, med 0, IQR 0-0) 9 of 11 (81 8%) perceived a shorter scan time for 3DUS than for CTA, MRA, and/or 2DUS (2 declined to answer) CTA inter-reader agreement on plaque presence is 11/14 (0 79, 95% CI 0 52-0 92) Expert interpretations of the first 120 3DUS agreed on 55 (0 45, 95% CI 0 37-0 55), disagreed on 35 (0 29, 95% CI 0 22-0 38), and one or both readers were “unsure” on 30 (0 25, 95% CI 0 18-0 33) Of 90 3DUS where both readers answered with certainty, there was 61% raw agreement (95% CI 0 51-0 71) For the first 264 expert 3DUS interpretations, sensitivity is 0 77 (95% CI 0 66-0 87), specificity 0 59 (95% CI 0 50-0 67), +LR 0 47, -LR 0 84, using the original CTA read as reference standard (excluding 42 “unsure”) Conclusion: POC 3DUS is time-efficient with good patient satisfaction and promising sensitivity Potential applications include initial diagnostic evaluation for neurologic symptoms or carotid bruit in low-resource settings [Formula presented]
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