Abstract: Microwave examination of individuals is carried out by transmitting microwave signals from multiple antenna locations into an individual and receiving the backscattered microwave signals at multiple antenna locations to provide received signals from the antennas. The received signals are processed to remove the skin interface reflection component of the signal and the corrected signal data are provided to a hypothesis testing process. In hypothesis testing for detecting tumors, image data are formed from the test statistic used to perform a binary hypothesis test at each voxel. The null hypothesis asserts that no tumor is present at a candidate voxel location. The voxel threshold is determined by specifying a false discovery rate to control the expected proportion of false positives in the image. When the test statistic value associated with a voxel is greater than the threshold, the null hypothesis is rejected and the test statistic is assigned to the voxel.

Abstract: A system and a method are provided for estimating the average dielectric properties of a plurality of regions in space. The application of this technique is illustrated for determining the average properties of breast tissue. The knowledge of average properties is important when UWB microwave radar signal processing algorithms are used for tumor detection and localization. The method is an extension of a time-domain inverse scattering algorithm based on the finite-difference time-domain method. A hybrid conjugate gradient optimization is used to minimize a cost function defined between a measured and a calculated total electromagnetic field at a series of antennas. The output of the method is an average set of electromagnetic material parameters that describe specific regions of interest in either a non-dispersive heterogeneous medium or a dispersive heterogeneous medium.

Abstract: Microwave imaging via space-time beamforming is carried out by transmitting microwave signals from multiple antenna locations into an individual to be examined and receiving the backscattered microwave signals at multiple antenna locations to provide received signals from the antennas. The received signals are processed in a computer to remove the skin interface reflection component of the signal at each antenna to provide corrected signal data. The corrected signal data is provided to a beamformer process that time shifts the received signals to align the returns from a scatterer at a candidate location, and then passes the time aligned signals through a bank of filters, the outputs of which are summed, time-gated and the power therein calculated to produce the beamformer output signal at a candidate location. The beamformer is then scanned to a plurality of different locations in the individual by changing the time shifts, filter weights and time-gating of the beamformer process.

Abstract: Microwave imaging via space-time beamforming is carried out by transmitting microwave signals from multiple antenna locations into an individual to be examined and receiving the backscattered microwave signals at multiple antenna locations to provide received signals from the antennas. The received signals are processed in a computer to remove the skin interface reflection component of the signal at each antenna to provide corrected signal data. The corrected signal data is provided to a beamformer process that time shifts the received signals to align the returns from a scatterer at a candidate location, and then passes the time aligned signals through a bank of filters, the outputs of which are summed, time-gated and the power therein calculated to produce the beamformer output signal at a candidate location. The beamformer is then scanned to a plurality of different locations in the individual by changing the time shifts, filter weights and time-gating of the beamformer process.

Abstract: An adaptive acoustic attenuation system has distributed nodal processing and a shared state nodal architecture. The system includes a plurality of adaptive filter nodes, each preferably having a dedicated digital signal processor. Each adaptive filter node preferably receives a reference signal and generates a correction signal that drives an acoustic actuator. Each adaptive filter node also shares nodal state vectors with adjacent adaptive filter nodes. The calculation of the nodal correction signals depends both on the reference signal and nodal state vectors received from adjacent adaptive filter nodes. The calculation of nodal state vectors shared with adjacent adaptive filter nodes depends on nodal state vectors received from other adjacent adaptive filter nodes as well as nodal reference signals inputting the adaptive filter node.

Abstract: Using a set of basis vectors, output from an adaptive control filter or adaptation of the control filter can be selectively constrained. Selected basis vectors define an adaptation subspace. The adaptive control filter can have a bank of non-adaptive FIR filters and a linear combiner with adaptive weights and fixed weights, or can use projection methods in conjunction with conventional adaptive FIR or IIR filter models. Filtered-X and filtered-U techniques can also be used.

Abstract: The effect of noise in the displayed information obtained from transcranial Doppler measurements is reduced by estimating the spectra of the returned Doppler signal as the average of Fourier spectra computed using multiple windows for the data being analyzed. The windows are chosen so that the spectra from different windows are approximately statistically independent, thereby reducing the variance of the spectrum by the averaging process. The Doppler data may be obtained by applying repeated pulses of ultrasonic energy to the head of a subject and isolating the Doppler frequency components of the return signal to obtain a set of data from a selected number of pulses. The data set so obtained has the multiple window functions applied thereto to obtain multiple windowed data sets which are operated on, as in a digital signal processor, to obtain multiple discrete Fourier transforms of the windowed data sets.

Abstract: Signals from plural electrodes placed at known positions on the head of an individual are digitized and processed in a computer processor which includes a bank of spatial filters. The filters are designed to meet a linearly constrained minimum variance criterion so that they each substantially pass signal energy from a location within the brain known with respect to the electrodes while rejecting signal energy from other locations within the brain. The outputs of the filters can be used to estimate the signal power at each of the locations in the brain, or the dipole moment at each location, and this information can be displayed on a display device to provide a map of source activity within the brain. The spatial filters do not require prior knowledge of the number of sources, and the number of discrete sources can be identified as well as the location, power, and dipole moment of the sources.