In Vivo Determination of the Complex Elastic Moduli of Cetacean Head Tissue
Abstract
The overall goal of this project is to determine the feasibility of in vivo, non-invasive measurement of the complex elastic moduli of cetacean head tissue. If this objective is met, measurement systems could be developed capable of measuring the complex elastic moduli of the head tissue of live, stranded cetaceans. The technical objective is to remotely generate and detect mid-frequency (1 to 10kHz) elastic waves within the body of a living cetacean, using ultrasound and to use the measured propagation parameters of these waves to obtain the complex elastic moduli by inversion. A further technical objective is to extract tissue moduli in this manner intracranially. This objective carries considerably more technical risk since both the wave-generating ultrasound and the probe ultrasound will be attenuated, distorted and scattered by the passage through the skull. The approach is to measure the complex shear and bulk modulus, from which all other moduli can be calculated. The shear modulus will be determined by measuring the speed and attenuation of shear waves generated within the tissue using focused ultrasound as a remote localized force generator. This general approach to determining the complex modulus is an application of a new medical imaging technology called elastography. The methods described by Greenleaf provide the basis for shear wave generation. Displacements are generated remotely in a tissue volume using one or more focused ultrasound beams. In the single-beam case, the ultrasonic carrier signal is modulated at a low frequency delta-f. In the dual-beam confocal configuration, the two ultrasonic signal carrier frequencies are offset from each other by 2-delta-f. In both cases, a radiation force at the focal point primarily generates shear waves at the frequency 2-delta-f.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2008
- Accession Number
- ADA505085
Entities
People
- David H. Trivett
- Peter H. Rogers
Organizations
- Georgia Tech