Anisotropy of High-Frequency Integrated Backscatter from Aortic Valve Cusps

Khan, Zamir; Boughner, Derek R.; Lacefield, James C.

doi:10.1016/j.ultrasmedbio.2008.02.001

« Previous Next »Ultrasound in Medicine and Biology
Volume 34, Issue 9 , Pages 1504-1512, September 2008

Anisotropy of High-Frequency Integrated Backscatter from Aortic Valve Cusps

Zamir Khan
- Biomedical Engineering Graduate Program, University of Western Ontario, London, Ontario, Canada
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada
Derek R. Boughner
- Biomedical Engineering Graduate Program, University of Western Ontario, London, Ontario, Canada
- Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
- Department of Medicine, University of Western Ontario, London, Ontario, Canada
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada
James C. Lacefield
- Biomedical Engineering Graduate Program, University of Western Ontario, London, Ontario, Canada
- Department of Electrical and Computer Engineering, University of Western Ontario, London, Ontario, Canada
- Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada
- Robarts Research Institute, University of Western Ontario, London, Ontario, Canada
- Address correspondence to: James Lacefield, Department of Electrical and Computer Engineering, University of Western Ontario, 279 Thompson Engineering Building, London, Ontario N6A 5B9, Canada

Received 15 October 2007; received in revised form 17 January 2008; accepted 4 February 2008. published online 14 April 2008.

Abstract

The biaxial anisotropy of integrated backscatter from aortic valve cusps was characterized ex vivo as an initial assessment of the suitability of high-frequency ultrasound for nondestructive evaluation of fiber alignment in tissue-engineered heart valves. Apparent integrated backscatter (AIB) from eight fresh, intact porcine cusps was measured over an 80° range of insonification angles using a 40-MHz ultrasound system. Angular dependence of backscatter was characterized by fitting a sinusoid to plots of AIB versus insonification angle for data acquired while rotating the transducer about the cusps in the circumferential and radial directions. Angular variations in backscatter were detected along both directions in individual specimens, although the mean amplitude of the fitted sinusoid was significantly greater for the circumferential data (12.1 ± 2.6 dB) than the radial data (3.5 ± 3.1 dB, p = 0.002). The higher angular variation of backscatter in the circumferential direction implies that collagen fibers in the fibrosa layer are the most prominent source of high-frequency scattering from porcine aortic valve cusps. The ability to characterize anisotropic backscattering from individual specimens demonstrates that high-frequency ultrasound can be used for nondestructive evaluation of fiber alignment in heart valve biomaterials. (E-mail: jlacefield@eng.uwo.ca)

Key Words: High-frequency ultrasound, Ultrasonic tissue characterization, Integrated backscatter, Anisotropy, Aortic valve