Ex vivo validation of 45 MHz intravascular ultrasound backscatter tissue characterization.
OBJECTIVE
The objectives of the present study are to describe the algorithm for VH(®) IVUS using the 45-MHz rotational IVUS catheter and the associated ex vivo validation in comparison to the gold standard histology.


RESULTS
The first phase of the present study was to construct the 45 MHz VH IVUS algorithm by using a total of 55 human coronary artery specimens [111 independent coronary lesions and 510 homogenous regions of interest (ROIs)], obtained at autopsy. Regions were selected from histology and matched with their corresponding IVUS data to build the plaque classification system using spectral analysis and statistical random forests. In the second phase, the ex vivo validation of the VH IVUS algorithm assessed a total of 1060 ROIs (120 lesions from 60 coronary arteries) in comparison with histology. In an independent manner, two interventional cardiologists also classified a randomly selected subset of the ROIs for assessment of inter- and intra-observer reproducibility of VH IVUS image interpretation.When including all ROIs, the predictive accuracies were 90.8% for fibrous tissue, 85.8% for fibro fatty tissue, 88.3% for necrotic core, and 88.0% for dense calcium. The exclusion of ROIs in the acoustically attenuated areas improved the predictive accuracies, ranging from 91.9 to 96.8%. The independent analysis of randomly selected 253 ROIs showed substantial agreement for inter-observer (k = 0.66) and intra-observer (k = 0.88) reproducibility.


CONCLUSIONS
Tissue classification by 45 MHz VH IVUS technology, when not influenced by calcium-induced acoustic attenuation, provided combined tissue accuracy >88% to identify tissue types compared with the gold standard histologic assessment, with high inter- and intra-observer reproducibility.
Department of Interventional Cardiology, Erasmus University Medical Centre, Rotterdam, The Netherlands Department of Interventional Cardiology Heart Institute (InCor), University of São Paulo Medical School, Sao Paulo, Brazil.
Carlos M
CM
Campos
Department of Biomedical Engineering, Cleveland Clinic Foundation, Cleveland, OH, USA.
Russell J
RJ
Fedewa
Department of Interventional Cardiology, Erasmus University Medical Centre, Rotterdam, The Netherlands Cardialysis, Rotterdam, The Netherlands.
Hector M
HM
Garcia-Garcia
Department of Biomedical Engineering, Cleveland Clinic Foundation, Cleveland, OH, USA.
D Geoffrey
DG
Vince
Keystone Heart Ltd, Caesarea, Israel.
M Pauliina
MP
Margolis
Department of Interventional Cardiology Heart Institute (InCor), University of São Paulo Medical School, Sao Paulo, Brazil.
Pedro A
PA
Lemos
Columbia University Medical Center, New York, NY, USA Cardiovascular Research Foundation, New York, NY, USA.
Gregg W
GW
Stone
Department of Interventional Cardiology, Erasmus University Medical Centre, Rotterdam, The Netherlands International Centre for Circulatory Health, NHLI, Imperial College London, London, UK.
Patrick W
PW
Serruys
Department of Biomedical Engineering, Cleveland Clinic Foundation, Cleveland, OH, USA Volcano Corporation, 3721 Valley Centre Drive, Suite 500, San Diego, CA 92130, USA anair@volcanocorp.com.
Anuja
A
Nair
D000465:Algorithms; D001344:Autopsy; D062906:Cardiac Catheters; D003331:Coronary Vessels / Q000000981:diagnostic imaging* / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D058226:Plaque, Atherosclerotic / Q000000981:diagnostic imaging* / Q000473:pathology; D015203:Reproducibility of Results; D012399:Rotation; D018084:Ultrasonography, Interventional / Q000295:instrumentation / Q000379:methods*
IVUS; VH IVUS; atherosclerosis; coronary disease; spectral analysis; vulnerable plaque