Room: Track 2
Purpose: Carotid plaques that are highly occlusive or that break or rupture can cause adverse health effects, including cognitive deficits or stroke. Quantitative ultrasound parameters enable noninvasive, inexpensive visualization of plaque vulnerability. We compute effective scatterer diameter (ESD) parameters of carotid plaque in-vivo and their relationships to surgical scores and histopathology assessments of excised plaque.
Methods: Ultrasound images and radiofrequency (RF) data were acquired from 52 individuals scheduled for carotid endarterectomy and from a reference phantom. Surgical side internal carotid artery plaques were segmented at end diastole. Frames were excluded from analysis when negative attenuation coefficient estimates exceeded 25 percent of estimates (n=120 frames included). Attenuation-corrected ESD (µm) in plaque was computed, and descriptive parameters were extracted. Surgical scores for cholesterol, calcium, thrombus, and ulceration (1-4) and histopathology assessments of representative H&E sections for percent cholesterol/fibrinoid, percent calcium, percent hemorrhage, and for hemosiderin and inflammation (0-3) were performed. Kendall’s tau correlation assessed relationships between ESD parameters, surgical scores, and histopathology assessments. Kruskal-Wallis H test evaluated ability of ESD parameters to distinguish among surgical scores and histopathology assessments.
Results: Participants were median(interquartile range)=73(10) years-old, 34.6 percent female, and 53.8 percent presented with symptoms of stroke or transient ischemic attack. Mode ESD correlated (correlation tau[p-value]) with surgical calcification score (0.17[0.041]). Average and Standard Deviation ESD correlated with histopathology hemosiderin score (-0.23[0.002]; 0.17[0.020]). Minimum ESD correlated with histopathology percent cholesterol/fibrinoid (-0.16[0.029]). Average ESD can distinguish between hemosiderin scores (?²[df=2]=10.62, p=0.005), especially scores 0 and 2, ?²(SE,Z,adjusted-p)=29.04(9.11, 3.19, 0.004). Standard Deviation ESD can also distinguish between hemosiderin scores (?²[df=2]=6.39, p=0.041), especially scores 0 and 2 ?²(SE,Z,adjusted-p)=-23.16(9.26, -2.50, 0.037).
Conclusion: ESD parameters correlate with tissue markers, including hemosiderin and calcification scores and percent cholesterol/fibrinoid. ESD parameters also can distinguish between hemosiderin scores, providing noninvasive insight into carotid plaque vulnerability.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by NIH grants F31HL141008 and R01NS064034. Steffel, Salamat, Wilbrand, Dempsey: no disclosures. Mitchell: Davies Publishing Inc, textbook author; Elsevier, Wolters-Kluwer, author textbook chapters, royalties; contracted research grants from W.L. Gore and Associates to UW-Madison. Varghese: research agreement with Siemens Medical Solutions for ultrasound research interface use.