Abstract 3772: High Precision and Accuracy of B-flow Ultrasound Morphometry of Internal Carotid Artery Stenosis: Improved Non-invasive Stenosis Grading

Abstract

Background: Evaluation of various imaging modalities for grading internal carotid artery (ICA) stenosis can be performed by comparison of minimal lumen diameters (MLD) as well as percent ICA-stenosis calculated with a healthy distal reference segment (NASCET method). The new B-Flow (BF) ultrasound (US) imaging method displays stenosis in a similar fashion as reference methods like catheter angiography (A) and multi-slice CT-angiography (MS CTA). Aim: to evaluate the accuracy of MSCTA by using multiplanar reformation (MPR) for measuring ICA stenosis compared with of A as well as accuracy and precision of BF-US compared with MSCTA at corresponding projections and locations. Methods and patients: CTA of ICA were compared with A in 37 low to high grade ICA stenoses of patients screened by doppler US velocity criteria. CTA were compared with US in 80 ICA stenoses of 63 patients in a similar fashion at identical projections. Diameters of stenosed ICA were rendered coaxial on CTA. A was made with AXIOM (Siemens, Germany), MSCTA with SOMATOM (Siemens, Germany); Ultrasound Logic 9 with 6-8 Mhz linear scanner, GE, USA. All readings were by two independent observers for each technique. Quantitative A was done with MEDIS software (Netherlands), Bland-Altman analysis and statistics with SPSS (Germany). Identical planes were confirmed by overlay technique. Results: MLD was slightly overestimated by CTA compared with angiography with mean differences (±SD) of 0.093 ± 0.25 mm for longitudinal sections. Pearson correlation coefficient (PCC) was 0.95. NASCET stenosis grade showed no bias between CTA and A (-0,5%±6.23% SD) and resulted in a PCC 0.93 for MPR's compared with A. MLD was slightly underestimated by parasaggital section (PSS) BF-US (0.031mm ± 0.23mm SD) compared with CTA, PCC = 0.96. NASCET ICA-stenoses were slightly underestimated by CTA, with mean differences of 1,16% ± 6,04% (SD), PCC was 0.92. In this cohort, discrimination of binary 50% NASCET stenosis with PSS BF-US had a 87%sensitivity, 86% specifity and an accuracy of 86%; discrimination of binary 70% NASCET stenosis with PSS BF-US had a sensitivity of 92%, specifity of 90% and an accuracy of 90%. Conclusion: diagnostic performance of CTA proved to be excellent compared with angiography and PSS 2D BF-US was highly accurate, when using corresponding projections. 2D BF-US may be a valuable additional tool for screening and confirmation of CAS for therapeutic stratification.