Medical image processing system

• US 5,172,419 A
• Filed: 03/05/1991
• Issued: 12/15/1992
• Est. Priority Date: 03/05/1991
• Status: Expired due to Term

• Current Assignee: CareStream Health Incorporated
• Original Assignee: Lumisys, Inc. (Eastman Kodak Company)
• Inventors: Manian, Bala S.
• Primary Examiner(s): Mancuso, Joseph
• Application Number:
  US07/665,401
• Time in Patent Office: 651 Days
• Field of Search: 382/6, 382/54, 382/44, 358/111, 364/413.13, 364/413.15, 364/413.19, 364/413.22, 364/413.24, 364/413.14, 364/413.16
• US Class Current: 382/132
• CPC Class Codes: G01T 1/2012 using stimulable phosphors, e.g. stimulable phosphor sheets
• CPC Class Codes: G03C 5/16 X-ray, infrared, or ultraviolet ray processes

Abstract

A system and method for processing images viewed on radiographic film. Such images include mammograms, CAT scans, or other standard x-ray type images. The system includes a scanning laser film digitizer for reading the optical density of pixels in an original film image; a controller which analyzes the image data based on input film type and scanned optical density in order to compute an exposure correction factor which enhances the original image quality; and a laser film writer which creates a new copy of the original data in the improved form. The system is capable of writing several proportional non-overlapping images on a single sheet of film. This feature facilitates diagnostic evaluation of related subject matter such as multiple angle views of an injury, simultaneous views of right and left side mammograms, or several CAT scans on a single exposure. The system uses a look-up table to store and access optical density vs. exposure characteristics for several types of radiographic film. This exposure data is used in image processing functions. The look-up table information is also used in the copy writing procedure to insure the correct exposure range is used for a given film type.

Claims

1. A system for manipulating radiographic type images comprising,

digital densitometer means, having a film support, a laser scanning device, a light detector and an analog-to-digital converter with an analog signal input connected to said light detector and a digital signal output, for creating a digital electrical signal, digital words in said digital electrical signal corresponding to the optical density of pixels comprising said radiographic image;

electronic storage means, connected to said densitometer, for receiving and storing said digital signal;

signal processing means connected to said storage means for systematically transforming the digital signal values in order to alter the optical characteristics of said image pixels and hence of said radiographic images, said signal processing means containing evaluation means for receiving original film type inputs, determining original exposure characteristics, and modifying original data to enhance the optical characteristics of subsequent copies by calculating proper exposure per image, regardless of film type said copy is written on; and

film writing means, connected to said processor means, having a film support, a modulated scanning laser device, and a data input for writing the transformed pixels to new film, producing a copy of said radiographic image.

2. The system of claim 1 wherien the signal processing means includes look-up table means containing reference numbers for transforming said digital signal values, said numbers corresponding to known exposure vs. optical density characteristics of radiographic type films.

3. A radiographic image formatting and writing apparatus comprising,

signal processing means, having a digital signal input, said digital signal input receiving input signals representing optical density information scanned from an underexposed radiographic image on a wide-dynamic-range radiographic film, a data storage register, exposure correcting means receiving said digital input signals from said storage register for adjusting said digital signals to correspond to a uniform increase in the exposure of said image and returning said adjusted digital signals to said storage register, scaling factor table means for accepting said adjusted digital signals from said storage register, and a digital output, each digital word corresponding to the optical density of an individual pixel, for determining appropriate dimensions of said image, mapping the digital information in an areawise manner and outputting mapped, formatted digital information, and

modulated laser writing means, having a film support, a digital signal input connected to said signal processing means for receiving said mapped formatted digital information, a laser, means for modulating said laser in response to said digital, and means for scanning a modulated beam from said laser, for scanning said modulated laser across a sheet of unexposed radiographic film in a manner such that the image written on said sheet of film corresponds to the image signals as mapped in said storage means.

4. The apparatus of claim 3 wherein said radiographic image is a mammogram.

5. A radiographic image formatting and writing apparatus comprising:

signal processing means, having a digital signal input, a data storage register, scaling factor table means for accepting digital signals representing pixel information for a plurality of radiographic images, and a digital output, each digital word corresponding to the optical density of an individual pixel, for determining appropriate dimensions of said image, mapping the digital information in an areawise manner, said plurality of radiographic images being mapped in a non-overlapping proportionally scaled manner and outputting said mapped, formatted digital information, and

modulated laser writing means, having a film support, a digital signal input connected to said signal processing means for receiving said mapped formatted digital information, a laser, means for modulating said laser in response to said digital, and means for scanning a modulated beam from said laser, for scanning said modulated laser across a sheet of unexposed radiographic film in a manner such that the image written on said sheet of film corresponds to the image signals as mapped in said storage means.

6. The apparatus of claim 5 wherein said plurality of images represents a time base study of a particular subject.

7. A system for manipulating radiographic images comprising,

a densitometer means, having a scannable laser device and an optical receiver, for scanning a radiographic film and producing an electric signal corresponding to the optical density of the scanned image, said original radiographic image having been taken underexposed on a low sensitivity, wide dynamic range type radiographic film;

analog-to-digital means for creating a digital signal corresponding to said electric signal;

storage means connected to said densitometer for storing digital signal values received from analog-to-digital converter;

a loop-up table containing exposure versus optical density for a plurality of radiographic film types, including said low sensitivity, wide dynamic range type radiographic film used for said original radiographic image;

a processor connected to said storage means for accessing said stored digital signal values, and connected to said look-up table for determining film exposures values corresponding to said digital signal values, said processor performing a transformation of optical density from the original underexposure to a second corrected exposure to form a transformed digital signal; and

film writing means, connected to said processor, for writing said transformed digital signal to new film, each transformed digital signal comprising an optical density value for an image pixel in a film copy.

8. The system of claim 7 wherien said original radiographic image is a mammogram.

9. The system of claim 7 wherein said processor performs a non-linear transformation on digital signal data, converting an original image to an image with transformed optical characteristics on a second film type.

10. A system for manipulating radiographic images comprising,

a densitometer means, having a scannable laser device and an optical receiver, for scanning a radiographic film and producing an electric signal corresponding to the optical density of the scanned image;

analog-to-digital means for creating a digital signal corresponding to said electric signal;

storage means connected to said densitometer for storing digital signal values received from analog-to-digital converter, said storage means storing the digital signal as pixels, formatting/mapping them in a representation of an areawise map;

signal processing means, having a digital signal input connected to said storage means, a data storage register, scaling factor table means for accepting digital signals representing pixel information for a plurality of radiographic images, and a digital output, for proportionally scaling the dimensions of the plurality of images to be copied in a manner such that the reduced plural images fit properly on a single film sheet, mapping the scaled digital information in an areawise manner and outputting said mapped, formatted digital information; and

film writing means, having a film support, a digital signal input connected to said signal processing means for receiving said mapped, formatted digital information, and a modulated laser scanning device responsive to said digital signal input for writing said images onto a sheet of unexposed radiographic film, wherein the film writing means writes a plurality of non-overlapping proportionally scaled images onto a single sheet of film.

11. A method for producing a mammogram comprising:

exposing a wide dynamic range radiographic film with a radiation source through mammary tissue in a manner whereby an underexposed, though viable image is generated in said film;

scanning said underexposed film image, once developed, in a densitometer whereby a digital signal is generated in accordance with the optical density of individual pixels of the radiographic image;

storing the digital signal;

informing a processing means of the film type used to generate the scanned image;

referring to data stored in a look-up table, said data including an exposure vs. optical density characteristic of a plurality of radiographic film types used in mammography;

comparing digitized scanned data with data in said table to determine the exposure of said image;

calculating a correction value required to maximize the image contrast on a specified radiographic film type;

modifying the recorded pixel data in a data processing device in accordance to exposure correction calculation, producing transformed pixel data corresponding to an image with modified optical characteristics;

mapping the transformed pixels in an areawise pattern within said processing device in a manner which supports writing to a second film of said specified film type; and

writing the transformed pixels to said second film which is of the type the exposure correction was calculated for, with a laser which is modulated and scanned across the second film in a manner so as to produce a transformed image, as mapped in the processing device.

12. A method for producing a mammographic study comprising:

(a) exposing a sheet of film with radiation transmitted through mammary tissue in order to produce a radiographic image;

(b) scanning said image to produce a digital signal corresponding to the optical density of individual pixels of which said image is composed;

(c) storing said image as a formatted set of digital values corresponding to a pattern of pixels;

(d) exposing a second radiographic sheet in a similar manner at a later time to produce a second image;

(e) digitizing and storing said second image in a similar fashion as first exposure; and

(f) recalling each exposure and mapping pixels whereby each successive image is shown on a single sheet of film in a reduced, non-overlapping manner so as to facilitate a time base study of said mammary tissue.