Method and system of compensation of thickness of an organ

• US 6,415,015 B2
• Filed: 12/21/2000
• Issued: 07/02/2002
• Est. Priority Date: 12/28/1999
• Status: Expired due to Term

• Current Assignee: GE Medical Systems Norway AS (General Electric Company)
• Original Assignee: GE Medical Systems Norway AS (General Electric Company)
• Inventors: Nicolas, Francois, Lienard, Jean, Muller, Serge, Soubelet, Elisabeth, Rick, Andreas
• Primary Examiner(s): BRUCE, DAVID VERNON
• Application Number:
  US09/745,886
• Publication Number:
  US 20010016030A1
• Time in Patent Office: 558 Days
• Field of Search: 378/4, 378/62, 378/98.7, 378/98.12
• US Class Current: 378/62
• CPC Class Codes: G06T 2207/10116 X-ray image
• CPC Class Codes: G06T 2207/30068 Mammography; Breast
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/92 based on global image properties

Abstract

Method and system for compensating for the thickness of an organ in a radiology instrument, in which an image of the radiological thicknesses of the organ through which the X-ray beam has passed is calculated on the basis of a digitized image, the thickness image is filtered using a low-pass filter in order to obtain a low-frequency image, the low-frequency image is subtracted from the radiological thickness image in order to obtain a contrast image, the low-frequency image is processed using a pre-recorded table taking into account a contract χ selected by a user in order to obtain an image with reduced dynamic range, and the image with reduced dynamic range is added to the contrast image in order to obtain a compensated thickness image, the pixels having a level below or above a predetermined threshold being returned at least to the value of the threshold, while preserving the differences and real ratios between the anatomical structures.

Claims

1. A method of compensation of thickness of an object in a radiological imaging apparatus having radiation source and a means of detection of the radiation source after it has crossed the object, the means of detection being capable of converting the radiation source into a digital electronic signal, in which, from a digitized image, an image of the radiological thicknesses of the object crossed by the radiation source is calculated, the image of radiological thicknesses is filtered by a low-pass filter in order to obtain a low-frequency image, the low-frequency image of radiological thicknesses is subtracted in order to obtain a contrast image, the low-frequency image is processed by a prerecorded table or calculated in real time taking into account a contrast χ

chosen by a user in order to obtain an image with reduced dynamics and the image with reduced dynamics and the contrast image are added in order to obtain a compensated thickness image, the pixels of level lower or higher than a predetermined threshold having been brought back at least to the value of the threshold, while preserving the differences and the real relations between the internal structures of the object.

2. The method according to claim 1, in which calculation of the image with reduced dynamics takes into account a range of gray levels of width and center indicated by a user.

3. The method according to claim 2, in which processing of the low-frequency image for obtaining the image with reduced dynamics is carried out in accordance with the width and center of the range of gray levels.

4. The method according to claim 1 in which processing of the low-frequency image for obtaining the image with reduced dynamics is carried out by means of a digital table or an analytical law.

5. The method according to claim 2 in which processing of the low-frequency image for obtaining the image with reduced dynamics is carried out by means of a digital table or an analytical law.

6. The method according to claim 3 in which processing of the low-frequency image for obtaining the image with reduced dynamics is carried out by means of a digital table or an analytical law.

7. The method according to claim 4, in which processing of the low-frequency image follows a monotone law.

8. The method according to claim 5, in which processing of the low-frequency image follows a monotone law.

9. The method according to claim 6, in which processing of the low-frequency image follows a monotone law.

10. The method according to claim 7, in which processing of the low-frequency law follows a linear law of slope α

.

11. The method according to claim 8, in which processing of the low-frequency law follows a linear law of slope α

.

12. The method according to claim 9, in which processing of the low-frequency law follows a linear law of slope α

.

13. The method according to claim 6, in which the slope α

evolves in a manner inversely proportional to the contrast χ

.

14. The method according to claim 11, in which the slope α

evolves in a manner inversely proportional to the contrast χ

.

15. The method according to claim 12, in which the slope α

evolves in a manner inversely proportional to the contrast χ

.

16. The method according to claim 1 in which a low-frequency image is stored in a memory and, on a change of contrast, the low-frequency image is read in the memory and the necessary processings and calculations are carried out.

17. The method according to claim 1 in which, on a change of contrast, the parameters of the filter applied to the image of radiological thicknesses by a low-pass filter are adapted in order to obtain a low-frequency image and the necessary processings and calculations are carried out.

18. A system of compensation of thickness of an object in a radiological imaging apparatus, of the type comprising a radiation source and a means of detection of the radiation source after it has crossed the object, the means of detection being capable of converting the radiation source into a digital electronic signal, including a means for calculating, from a digitized image, an image of the radiological thicknesses of object crossed by the radiation source, low-pass filter for obtaining radiological thicknesses from the image, a low-frequency image, means for subtracting the low-frequency image from the radiological thicknesses in order to obtain a contrast image, means for processing the low-frequency image according to a prerecorded table taking into account a contrast χ

chosen by a user in order to obtain an image with reduced dynamics and means for adding the image with reduced dynamics and the contrast image in order to obtain a compensated thickness image, the pixels of level lower or higher than a predetermined threshold having been brought back at least to the value of the threshold, while preserving the differences and the real relations between the features of the object.