This paper reports on a new ultrasound device for noninvasive assessment of bone. The device, known as the QRT 2000 -for Quantitative Real-Time-is entirely self-contained, portable, and handheld. The QRT 2000 is powered by 4 “AA” rechargeable batteries and permits near real-time evaluation of a novel set of ultrasound parameters and their on-line display to the user. The parameters have been studied both in vitro and clinically with a laboratory unit that measured the calcaneus in through transmission and computed the ultrasound features off-line. The data related the ultrasound parameters to the bone mineral density (BMD) of the calcaneus, spine and hip, as determined by x-ray absorptiometry, and demonstrated that the parameters were superior to the standard ones known as BUA and SOS (broadband ultrasound attenuation and speed-of-sound, respectively). The QRT 2000 was then constructed to compute the same parameters; however as noted about it does this in near real-time and provides visual feedback to the user while the measurements are being made. The compactness and portability of the unit make it also ideal for spaceflight applications. Finally, the QRT 2000 was designed to be manufactured at relatively low cost, and therefore should enable the significant expansion of quantitative ultrasound measurements to, for example, primary care physicians in this country and abroad, and including for use in the developing world.
Development of ultrasound nondestructive evaluation techniques (NDT) has involved a combination of both analytic and experimental methods. In contrast, relatively little work has been done on the use of computational methods for experimental design and analysis in NDT. This is due to the relative lack of availability of software for such computations. While computational methods and associated software implementations abound in the electromagnetic and structural analysis engineering communities, no such paradigm exists for ultrasound researchers and engineers. This paper demonstrates a software package, Wave2000, which computes the full solution to the 2D viscoelastic wave equation. 2D objects are represented by graphical images and are comprised of a number of solids and/or liquids. Each material is specified in terms of its material density, the first and second Lame constants, and the first and second viscosities. The program computers the displacement vector was a function of Cartesian coordinates x and y and of time t, and the solution includes effects of diffraction, scattering, reflection, and attenuation of the propagating wave. Wave2000 implements a finite difference solution on a standard personal computer running Microsoft Windows 95 or NT. Sources and receivers may be located anywhere in or on the surface of the object. The source waveform can be practically any temporal function desired, including data collected from an actual transducer, and the receiver data can be sorted in a data file for subsequent processing. Several examples of the use of Wave2000 are given, including simulations of scattering from cracks and propagation through layers of materials and fluid-filled porous structures. Results demonstrate that computational methods can play an important can play an important role in NDT specifically and in ultrasonics in general.
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