CCD and phosphor screen digital radiology apparatus and method for high resolution mammography

• US 5,142,557 A
• Filed: 12/21/1990
• Issued: 08/25/1992
• Est. Priority Date: 12/21/1990
• Status: Expired due to Term

• Current Assignee: Roper Scientific Incorporated (Roper Technologies, Inc.)
• Original Assignee: Photometrics, Ltd. (Teledyne Technologies Incorporated)
• Inventors: Hunter, Tim B., Toker, Emre, Roehrig, Hans
• Primary Examiner(s): Howell, Janice A.
• Assistant Examiner(s): CHU, KIM KWOK
• Application Number:
  US07/633,212
• Time in Patent Office: 613 Days
• Field of Search: 378/62, 378/98, 378/4, 378/99.37, 378/64, 378/65, 378/145, 378/146, 378/901, 358/111, 250/370.08, 250/370.09, 250/363.04, 250/363
• US Class Current: 378/37
• CPC Class Codes: A61B 6/4216 using storage phosphor screens
• CPC Class Codes: A61B 6/4488 Means for cooling A61B6/045 takes precedence
• CPC Class Codes: A61B 6/502 for diagnosis of breast, i.e. mammography
• CPC Class Codes: H04N 1/393 Enlarging or reducing
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30
• CPC Class Codes: H05G 1/60 Circuit arrangements for obtaining a series of X-ray photographs or for X-ray cinematography
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

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.

Claims

1. A radiology device for imaging tissue, comprising:

(a) a controlled x-ray source for directing x-rays through the tissue;

(b) a screen positioned to receive x-rays existing from the tissue for producing a light image in response to the exiting x-rays;

(c) a cooled, slow scan CCD camera;

(d) means for optically coupling light emitted by the screen into said CCD camera;

(e) means for operating said camera to produce analog information representing an image of the tissue and means for converting the analog information to digital information;

(f) means for storing the digital information as a representation of the light image in response to the digital information;

(g) means for marking a location of a portion of said light image having at least a certain density variation;

(h) means for reducing the x-ray dosage to a level at which an image of predetermined resolution of the marked portion is produced;

(i) wherein said reducing means reduces the x-ray dosage to a level at which only a radiopaque needle inserted into a digitally marked region is imaged;

(j) said reducing means including means for reducing the x-ray dosage by the ratio ##EQU4## where L_f is the width of the field of view of the cooled, slow scan CCD camera, L_i is the width of a region of interest within the field of view, and L_CCD is the width of a rectangular CCD detector array in the cooled, slow scan CCD camera.

2. A device for imaging tissue, comprising:

x-ray a controlled source for directing x-rays through x-ray transmissive tissue of given dosages;

an x-ray sensitive screen for forming an image in response to x-rays passing through the tissue;

optical means optically coupled to said screen for forming digital signals representing a selected portion of the image;

said optical means including field-of-view varying means for defining the size and location of the selected portion; and

control means responsive to the digital signals for reducing the level of the x-ray dosage of said x-ray source by an amount corresponding to the reduction in size of the selected portion with respect to the size of the original field of view.

3. The device of claim 2 wherein the device includes a cooled, slow scan CCD camera and the x-ray dosage control means includes means for reducing the x-ray dosage by the ratio ##EQU5## where L_f is the width of the field of view of the cooled, slow scan CCD camera, L_i is the width of a region of interest within the field of view, and L_CCD is the width of a rectangular CCD detector array in the cooled, slow scan CCD camera.