Photometrics, Ltd.

Infimed, Inc.

Hans Roehrig

William J Dallas

Emre Toker

Thomas L Vogelsong

Tim B Hunter

Eugene J Gross

An x-ray or gamma ray image that is produced as an array of pixels is treated for reduction or elimination of white spot noise. Two or more successive images in registry are produced and the pixel values at each pixel location are inspected for the respective images. The pixel values are considered according to rank, e.g. from dark to bright, and the lowest ranking pixel value is selected for each pixel location. This creates an output image that is substantially free of the spot noise that results from direct impingement of the x-ray photons on the imaging device. This technique is especially useful in portal imaging for radiation therapy, dental imaging, or industrial imaging.

Image spot noise reduction employing rank order

A system for locating a region of varying density in biological tissue such as a breast includes a controlled x-ray source for directing x-rays through the breast, a phosphor screen positioned to receive x-rays exiting from the tissue and producing light in response thereto, a cooled, slow scan CCD camera, a variable magnification optical system positioned to receive light emitted by the phosphor screen and directing it to the cooled, slow scan CCD camera, a high resolution monitor, and a control system receiving signals from the cooled, slow scan CCD camera and digitizing the signals to produce digital data representative of the densities of various locations of the tissue. The control system includes a processor operated to determine a signal-to-noise ratio of light received by the cooled, slow scan CCD camera from the variable magnification optical system and to control the intensity of x-rays in response to the signal-to-noise ratio to determine locations of the object at which the corresponding densities exceed a certain level. The addresses of such locations are stored. The variable magnification optical system is controlled to focus and enlarge 'digitally marked' locations of the object so images thereof substantially fill a screen of the monitor. In one described embodiment, the system is used in conjunction with a radiopaque needle localization process to rapidly and precisely identify locations of high density breast tissue which are likely tumor and/or microcalcification sites.

CCD and phosphor screen digital radiology apparatus and method for high

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Tucson, AZ, United States of America

Hans Roehrig