Mathematics and Physics of Emerging Biomedical Imaging (1996) / Chapter Skim
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7 ULTRASONICS
7 ULTRASONICS
Pages 121-132
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From page 121... ...
This pulse is reflected from the various scatterers and reflectors within the tissue under investigation. The scattered pressure wave is detected by the transducer array and focused using electronic beam forming.
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From page 122... ...
electromechanical properties of piezoelectric en cl ferroelectric materials. Field Distributions The seminal references in this area are, of course, related to the classic diffraction theory of Huygens and various analyses by Rayleigh, Kirchoff, and Sommerfeld.
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From page 123... ...
In recent years, the KEM model has been particularly useful for transducer design and is currently used widely in this regard. 7.2.2 Ultrasonic Beam Forming Phased array transducers contacting the surface of an object can be electronically scanned and focused to produce real-time images of internal structures.
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From page 124... ...
Currently a number of simple theories are used to model pieces of the imaging system: geometric optics for fixing transmit aperture (f-number) , Fourier optics for apo(lization and control of side lob es, sampling theory for array design and system electronics, and statistical considerations for setting system dynamic range and color flow estimates.
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From page 125... ...
Tracking the probe movement provides a "compounding effect" to improve gray scale images and reduces noise in color flow imaging. Tracking the blood or tissue movement produces color Doppler and tissue motion imaging with direction, speed, and Doppler power information.
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From page 126... ...
Better resolution cannot be obtained at high frequencies without putting the transducers closer to the tissue to be imaged, and an understanding of absorption is quite important to our use of scattered waves. Attenuation is thus a factor that influences the image when using scattered waves.
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From page 127... ...
. The investigation of tissue properties at the levels suggested above could be done by further development and application of diffraction tomography using laboratory techniques.
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From page 128... ...
· Further study of the dielectric and ferroelectric properties of materiais, with particular emphasis on the development of new ferroelectrics with high dielectric constants, such as the relaxer ferroelectrics; of ferroelectric functions; and of the role of grain and domain boundaries in the piezo- and ferroelectric properties of materials. · Development of four-dimensional finite-element models of single transducer elements and multielement arrays.
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From page 129... ...
and thus allow optimal utilization of existing three-dimensional reconstruction techniques. Development of methods for region segmentation as a preprocessing step to measurements of both area and volume, and application of three-dimensional image data display methods and automatic methods for measuring areas anct volumes.
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From page 130... ...
10. Leedom, D.A., Krimholtz, R., and Matthei, Gab., Equivalent circuits for transducers having arbitrary even or odd symmetry piezoelectric excitation, IEEE Trans.
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From page 131... ...
19. Stepanishen, P.R., Transient radiation from pistons in an infinite planar baffle, ]
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