Tomosynthesis X-ray mammogram system and method with automatic drive system

#The present invention relates generally to an imaging system, and more particularly to an X-ray mammogram tomosynthesis system.

#Conventional X-ray mammography imaging systems utilize an X-ray source mounted on a supporting frame. The frame is manually rotated by the system operator to a place the X-ray source into desired position adjacent to a patient's breast. The X-ray source emits a first shot of X-rays through the patient's breast and an image is captured on a first an X-ray sensitive film positioned on the opposite side of the patient's breast. The frame is then manually rotated into another position by the operator and a second X-ray sensitive film is exposed by a second shot of X-rays. This procedure can be repeated several times to generate several images on different films. The images on the X-ray sensitive films may then be evaluated by a physician and/or digitized and evaluated by a computer. However, such a system produces a two dimensional image of the patient's breast, which provides insufficient information about the presence of tumors and calcification and often leads to false positive readings.

#U.S. Pat. No 5,872,828 discloses a tomosynthesis system for breast imaging. This system produces a three dimensional image of the breast being imaged. The tomosynthesis system contains an X-ray source which moves in an arc shaped path over the breast that is being imaged, a stationary digital X-ray detector and an image processor. The detector is mounted on a stationary portion of a support structure. The X-ray source is mounted on a movable portion of the support structure. The movable portion of the support structure is an arm whose lower end is rotatably attached to the stationary support structure at a pivot point, and whose upper end supports the X-ray source.

#FIG. 1 is schematic illustration of a system according to the first preferred embodiment of the invention.

#FIG. 2 is a side view of a system according to the first preferred embodiment of the invention.

#FIG. 3 is schematic illustration of a system according to the second preferred embodiment of the invention.

#The present inventors have discovered that X-ray tomosynthesis imaging system speed and accuracy can be improved by using a track and a mechanical drive system which can position an X-ray source at any angle between the vertical to horizontal position on an arc shaped path. The track reduces the vibration of the X-ray source and reduces the driving power required to move the X-ray source.

#The X-ray source is moved in a stepped motion (i.e., in a sequence of angle increments) about an arc shaped path by the mechanical driving mechanism at a high rate (about 0.1-1.5 seconds per step). The arc shaped path is a path that comprises a portion of a circle or a curved line. While less preferred, the path of the X-ray source may include a full circle, ellipse or polygon. A stationary electronic detector (i.e., an electronic device which detects X-rays, rather than an X-ray sensitive film) is used to detect the X-rays emitted by the X-ray source and attenuated by the imaged object.

#The imaging system also contains an image processor, such as a general or special purpose computer or a microprocessor chip, such as an ASIC chip. The processor is electrically connected to the electronic detector. The processor forms a three dimensional image of an imaged object from a signal output by the electronic X-ray detector. The processor may use any suitable algorithm to reconstruct a three dimensional image of an imaged object from an arc shaped X-ray source scan. For example, such an algorithm is disclosed in related U.S. patent application Ser. No. 10/______, (attorney docket number 040849/0186), to Jeffrey Eberhard and Bernhard Claus titled “Generalized Filtered Back-Projection Reconstruction In Digital Tomosynthesis ” filed on the same date as the present application and incorporated herein by reference in its entirety. While less preferred, the method disclosed in U.S. Pat. No. 5,872,828, incorporated herein by reference in its entirety, may also be used. If desired, the processor may also be used to control the mechanical driving mechanism motion. Alternatively, a separate controller, such as a computer, microprocessor chip or a motor controller, may be used to control the mechanical driving mechanism motion. In this case, the controller is synchronized with the image processor.