Methods and apparatus are provided for detecting an abnormality in a host medium, such as a tumor within a patient's breast. The host medium is initially illuminated at a plurality of different positions with light of at least two different wavelengths. Following the propagation of the signals through the host medium, the amplitude and phase of the signals are detected and, based upon the detected signals, a shadow image can be created in which the abnormality is depicted as a suspicious region. Once a suspicious region has been identified, at least that portion of the host medium that contains the suspicious region is again illuminated with frequency-swept modulated signals of at least two different wavelengths generated by the light source and modulated by a modulator, such as a network analyzer. Based upon the detected signals that have propagated through at least that portion of the host medium that includes the suspicious region, a P-criteria can be determined that is dependent upon the coefficient of absorptivity of the host medium and embedded abnormalities. Likewise, an Svar-criteria can be determined based upon concentrations of oxygenated hemoglobin and deoxygenated hemoglobin. Based upon at least these criteria which reflect physiological parameters of the host medium and embedded abnormalities as well as the possible comparison of the shadow images to an x-ray image of the host medium, the abnormality can be characterized. In addition, an apparatus is provided that facilitates the compression of a patient's breast in order to improve the resulting images.

Method and apparatus for detecting an abnormality within a host medium utilizing frequency-swept modulation diffusion tomography

The detection method and apparatus detects abnormalities having a first signal propagation property within a host medium having a second signal propagation property based upon signals which have been reflected, scattered and/or absorbed by the host medium and any abnormalities therein. The detection apparatus includes a signal source for introducing a signal into the host medium which varies with respect to a predetermined signal parameter, such as time, frequency or source location. The detection apparatus also includes a plurality of detectors disposed along some or all of the boundary of the host medium for detecting the signal following propagation through the host medium and any abnormalities within the host medium. The detection apparatus further includes a signal processor for constructing at least one partial differential equation to describe the propagation of a regularized signal through a medium having the same shape as the host medium. The signal processor eliminates at least one term which includes a perturbation function based, at least in part, upon the signal propagation properties of the abnormality. The signal processor can then determine the solution of the at least one partial differential equation and can, in turn, recover the perturbation function. As a result, the detection apparatus can detect abnormalities within the host medium in an accurate, efficient, fast and cost effective manner.

Method and apparatus for detecting an abnormality within a host medium

Underwater acoustic communications (UAC) at the reverberation-limited range results in severely distorted information signals. Wide-band signals are subject to both intermodal and intramodal-type of dispersions. The underwater acoustic channel impulse response and the sidelobes strongly depend on the waveguide structure and the source and receiver positions. The motion and displacement from this position, as well as other environmental variabilities impose a real-time adaptivity for the receiver operation to keep track of the fluctuations. To increase the system's reliability and data rate, there is a need to employ adaptive equalizers and diversity techniques to improve the margins against noise, and intersymbol interference (ISI). Blind adaptive equalization (BAE) is the ideal adaptive compensation when operating point-to-multipoint networks, and centralized communication systems in general. Inherent optimum multiple resonant modes within the ocean acoustic waveguide can be exploited judiciously via a new proposed parallel data multicarrier modulation (MCM) scheme by sending data over the multiple subcarriers. MCM might eventually obviate equalization which introduces higher-order computational complexity to the receiver. The above modulation eliminates multipaths and allows operation at multiples of the single-carrier transmission rate. The system's immunity to distortions such as ISI, fast fades, and impulsive noises, is increased due to incorporation of symbol guard space. Direct comparisons with single carrier schemes (such as higher-order statistics (HOS)-based equalization) are of great interest, since the proposed new receiver configuration has low-complexity to provide a compact, portable and low-power practical acoustic modem. Finally, network topology issues are considered to determine optimum network architectures for underwater acoustic LANs. A central topology (CT) supported by BAE and MCM transmission is proposed.

Compound compensation strategies for wireless data communications over the multimodal acoustic ocean waveguide

An overview of the unique challenges in underwater acoustic (UWA) communication in ocean environment is presented. The UWA channel is compared with conventional RF channels. Several design considerations applicable to the physical layer design of a UWA communication system is described based on field measurements. The unique problems in synchronization under high Doppler are described highlighting the key differences in the way Doppler affects the RF and UWA channels. A novel timing synchronization mechanism has been introduced in this study which caters for both the sampling skew offset and the Doppler shift between the transmitter and the receiver.

Underwater acoustic communications: Design considerations at the physical layer based on field trials

In this paper, we analyze the mutual information of sensor networks in an underwater wireless communication system by placing the acoustic sensor nodes at different location in order to achieve optimum mutual information. The performances of acoustic sensors nodes are observed and analyzed by placing the sensors in collaborative and parallel channel network system. Different numerical calculation and experimental observation for both network systems such as information loss, bit error rate, mutual information, and channel capacity are considered.

On the Mutual Information of Sensor Networks in Underwater Wireless Communication: An Experimental Approach

A variety of signal processing functions are performed by Underwater Acoustic Systems. These include: 1) detection to determine presence or absence of information signals in the presence of noise, or an attempt to describe which of a predetermined finite set of possible messages {mi,i,...,M} the signal represents; 2) estimation of some parameter θˆ associated with the received signal (i.e. range, depth, bearing angle, etc.); 3) classification and source identification; 4) dynamics tracking; 5) navigation (collision avoidance and terminal guidance); 6) countermeasures; and 7) communications. The focus of this paper is acoustic communications.

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High-rate wireless data communications: An underwater acoustic communications framework at the physical layer

This paper describes a novel method for detection of object characteristics using coherent imaging methods. Experimental results are presented. The technique is particularly useful for identifying known or desired features of the object being illuminated and is suited for detection under adverse conditions. A system was demonstrated that generates real-time surface contours with zoom capability using a spatial modulation approach. The system is unique in that it uses video technology to generate patterns from a single variable spacing projection grating. In the demonstrated projection system, the distorted target grating is processed with a spatially matched filter. This is a binary optical filter that passes information selectively. By using a special video processor, this situation may be duplicated electronically. The output of the video processor circuit can be an image showing equal depth contours superimposed on the target or may be designed to produce different electronic signature information such as texture information. In addition, noise reduction techniques have been used to reduce or remove the regular and distorted grating features, while retaining object contours. The adaptation of this method to turbid or scattering media is an object of current research. The approach relies upon coherent signal processing techniques to recover generated patterns broadcast from the illumination device against the background.

Underwater detection using coherent imaging techniques

On overview of optical technologies, active and passive components, and systems that are deemed suitable for wireless communications is presented in this paper. Specifically addressed is the use of onboard photonics in advanced spacecraft, satellite, etc. for applications in wireless communications. To assess its viability in potential commercial applications, the state-of-the-art of phonics technology and future prospects for economical large capacity multi-channel services is briefly reviewed.

Anthony G. Bessios

Papers

High-rate wireless data communications: An underwater acoustic communications framework at the physical layer

Underwater detection using coherent imaging techniques

Frequency division multiplexing in wireless underwater acoustic LANs