Three-dimensional isotropic wavelets for post-acquisitional extraction of latent images of atherosclerotic plaque components from micro-computed tomography of human coronary arteries.
OBJECTIVE
The capability of wavelet transforms to separate signals into frequency bands is the basis for its use in image compression and storage, data management and transmission, and, recently, extraction of latent images of tissue components from noisy medical images. Analysis of temporal variations of radiofrequency backscatter of intravascular ultrasound with one-dimensional wavelets can detect lipid-laden plaque in coronary arteries with a sensitivity and specificity of >80%. In this study we evaluate the capability of a novel, 3-dimensional isotropic wavelet analysis to perform high resolution, non-directionally biased, statistically reliable, non-invasive discrimination between components of human coronary atherosclerotic plaques in micro-CT.


METHODS
Coronary artery segments (5-15 mm) were excised at necropsy from 18 individuals with advanced coronary atherosclerosis. Specimens were imaged using a GE Locus SP ex vivo micro-CT scanner and processed for histological correlation (833 sections). The isotropic wavelet constructs were applied to the entire volume of CT data of each arterial segment to distinguish tissue textures of varying scales and intensities. Voxels were classified and plaque characterization achieved by comparing the relative magnitudes of these wavelet constituents to that of several reference plaque tissue components.


RESULTS
Processing of micro-CT images via these isotropic wavelet algorithms permitted 3-D, color-coded, high resolution, digital discrimination between lumen, calcific deposits, lipid-rich deposits, and fibromuscular tissue providing detail not possible with conventional thresholding based on Hounsfield intensity units. Using the isotropic wavelets (with histology as the gold standard), lipid-rich pools approaching the size of the filter for the isotropic wavelet algorithm (0.25 mm [250 microns] in length) were identified with 81% sensitivity and 86% specificity. Calcific deposits, fibromuscular tissue, and lumen equal to or larger than the wavelet filter size were detected without error (100% sensitivity and specificity).


CONCLUSIONS
Isotropic wavelet analysis permits high resolution, multi-dimensional identification of coronary atherosclerotic plaque components in micro-CT with sensitivity and specificity similar to that achieved with data obtained invasively (from IVUS in vivo) using one-dimensional wavelets. Further studies are necessary to test the applicability of this technology to clinical, multi-detector scanners.
Texas Heart Institute, St. Luke's Episcopal Hospital, Houston, TX 77030, USA. Gertz@cc.huji.ac.il
S David
SD
Gertz
Bernhard G
BG
Bodmann
Deborah
D
Vela
Manos
M
Papadakis
Ibrahim
I
Aboshady
Paul
P
Cherukuri
Simon
S
Alexander
Donald J
DJ
Kouri
Shikha
S
Baid
Alex A
AA
Gittens
Gregory W
GW
Gladish
Jodie L
JL
Conyers
Dianna D
DD
Cody
Lilach
L
Gavish
Reza M
RM
Mazraeshahi
Wayne T
WT
Wilner
Lorraine
L
Frazier
Mohammad
M
Madjid
Alireza
A
Zarrabi
Serhiy
S
Lukovenkov
Amany
A
Ahmed
James T
JT
Willerson
S Ward
SW
Casscells
D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002114:Calcinosis / Q000000981:diagnostic imaging / Q000473:pathology; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000473:pathology; D003331:Coronary Vessels / Q000473:pathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008055:Lipids; D008297:Male; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000000981:diagnostic imaging / Q000473:pathology; D011856:Radiographic Image Enhancement / Q000379:methods; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
D008055:Lipids