Noninvasive quantitative tissue characterization and two-dimensional color-coded map of human atherosclerotic lesions using ultrasound integrated backscatter - Comparison between histology and integrated backscatter images

OBJECTIVES The purpose of the present study was to define clinicopathologic ally whether integrated backscatter (IB) combined with conventional two-dim ensional echo (2DE) can differentiate the tissue characteristics of calcifi cation (CL), fibrosis (FI), lipid pool (LP) with fibrous cap, intimal hyper plasia (IH) and thrombus (TH) and can construct two-dimensional tissue plaq ue structure in vivo. BACKGROUND It is difficult to characterize the components of plaque using c onventional 2DE techniques. METHODS Integrated backscatter values of plaques were measured in the right common carotid and femoral arteries (total 24 segments) both during life a nd after autopsy in 12 patients (age 68 to 84 years, 10 men and two women). Integrated backscatter values were determined using a 5-12 MHz multifreque ncy transducer, setting the region of interests (ROIs) (11 x 11 pixels) on the echo tomography of the entire arterial wall (55 +/- 10 ROI/segment) and comparing it with histologic features in the autopsied arterial specimens. RESULTS Corrected IB values obtained before death and at autopsy were signi ficantly correlated (r = 0.93, p < 0.01). Corresponding to the histologic f eatures, corrected IB values on the rectangle ROIs obtained during life wer e divided into five categories: category 1 (TH) 4 < IB less than or equal t o 6; category 2 (media and IH or LP in the intima) 7 < IB <less than or equ al to> 13; category 3 (FI) 13 < IB <less than or equal to> 18, category 4 ( mixed lesion) 18 < IB <less than or equal to>27 and category 5 (CL) 28 < IB <less than or equal to> 33. In category 2, media and intima were different iated using conventional 2DE. Under the above procedures, color-coded maps constructed with IB-2DE obtained during life precisely reflected the histol ogic features of media and intima. CONCLUSIONS Integrated backscatter with 2DE represents a useful noninvasive tool for evaluating the tissue structure of human plaque. (J Am Coll Cardi ol 2001;38:486-92) (C) 2001 by the American College of Cardiology.