Abstract: An ultrasound method and apparatus for classification of tissue in a region of interest in a body. The raw ultrasound return data is digitized and processed without the need for human visual analysis of pixel-scale video images. Tissue classification is done by correlation of the relative amount of energy in selected frequency bands of the power spectrum of the returned demodulated ultrasound data to that of known tissue samples.

Abstract: In a gyro-monotron oscillator a single, "monotron" cavity is used to interact with the electron beam. To handle very high powers without excessive cavity loss, the cavity is excited in a higher order mode such as TE.sub.0m1. Other modes can be resonant in the cavity, interfering with the operation when their frequency is near the operating frequency.To increase the mode separation, an upstream section of the cavity is made smaller, to support only a lower-order mode such as TE.sub.011. Also, the beam is pre-bunched by this lower order, interference-free mode so has less tendency to interact with spurious modes in the higher order cavity.

Abstract: For conducting very high microwave power at very high frequencies, circular waveguide transmitting a circular-electric-field mode is used. The vacuum-tight window of an electron tube is often the element with lowest power-handling capability. The inventive window has two dielectric plates with a space between them. There is a gap in the waveguide inner wall through which a dielectric fluid is circulated between the plates to cool them. The gap leads to a region containing wave-absorbing material such as water to absorb modes other than the circular-electric-field mode.