Incremental value of parametric quantitative assessment of myocardial perfusion by triggered Low-Power myocardial contrast echocardiography
Eric H. C. Yu, MD, MEd, FACC*,*,
Danny M. Skyba, PhD ,
Howard Leong-Poi, MD ,
Cairrine Sloggett, RN, RDCS*,
Michal Jamorski, RDCS*,
Rohit Garg, MSEE,
R. Mark Iwanochko, MD, FACC* and
Samuel C. Siu, MD, SM, FACC*
* Gordon Yu Hoi Chiu Echocardiographic Laboratory, The Toronto Western Hospital, Toronto, Canada
St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada
Philips Ultrasound, Bothell, Washington, USA
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Figure 1 An assisted border detection algorithm was employed to segment the myocardium from the rest of the ultrasound image. An exponential curve-fitting function of the form—I(t) = A(1 – exp–ßt)—was fit to the intensity vector from each pixel position in the segmented cine loop, where I(t) represents the intensity of a pixel as a function of time; A represents the intensity of full myocardial replenishment; and ß represents the rate constant of intensity change. The parameters of A and ß were automatically tabulated according to the pixel position and scaled, and a color map was applied to generate parametric images (four panels on the right) of blood volume (A image), blood velocity (ß image), and myocardial blood flow (A x ß image) of each pixel in the myocardium. A goodness-of-fit map for the data was also generated by the algorithm.
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Figure 2 This graph demonstrates the percentage of agreement between myocardial contrast echocardiography and single-photon emission computed tomography (SPECT) perfusion scores, where segmental perfusion scores are available for both modalities. Rates of agreement for visual cine loop assessment (VIS), myocardial parametric quantification image assessment (MPQ), and VIS + MPQ were 83%, 89%, and 92%, and kappa values were 0.46, 0.58, and 0.68, respectively (white bars). Rates of agreement for the classification of a moderate to severe perfusion defect for VIS, MPQ, and VIS + MPQ were 92%, 97%, and 97%, and kappa values were 0.53, 0.76, and 0.81, respectively (black bars).
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Figure 3 The upper panels demonstrate a contrast-enhanced apical four-chamber echocardiographic image at rest (left) alongside its corresponding parametric (middle), and single-photon emission computed tomography (SPECT) image (right). The bottom panels demonstrate a contrast-enhanced apical four-chamber echocardiographic image at peak stress (left) alongside its corresponding parametric (middle), and SPECT image (right). The parametric image has been color-coded: red indicates a moderate to severe perfusion deficit; yellow indicates a mild deficit; and green indicates normal perfusion. A stress-induced perfusion defect has developed in the apical segments (arrows), with apical thinning. The basal lateral segment on the parametric image was classified as nonanalyzable, using the goodness-of-fit image.
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