X-ray examination apparatus and method for forming an X-ray image

• US 7,003,146 B2
• Filed: 04/20/2001
• Issued: 02/21/2006
• Est. Priority Date: 04/20/2000
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Jung, Norbert, Eck, Kai, Meulenbrugge, Hendrik Jan
• Primary Examiner(s): Johns, Andrew W.
• Assistant Examiner(s): EDWARDS, PATRICK L
• Application Number:
  US09/838,890
• Publication Number:
  US 20010038706A1
• Time in Patent Office: 1,768 Days
• Field of Search: 382/128, 382/131, 382/132, 382/260, 382/262, 378/48.8, 378/207
• US Class Current: 382/132
• CPC Class Codes: A61B 6/582 Calibration
• CPC Class Codes: G06T 2207/10116 X-ray image
• CPC Class Codes: G06T 2207/30004 Biomedical image processing
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/77 Retouching; Inpainting; Scratch removal
• CPC Class Codes: G06T 7/0002 Inspection of images, e.g. flaw detection
• CPC Class Codes: H04N 25/683 by defect estimation performed on the scene signal, e.g. real time or on the fly detection
• CPC Class Codes: H04N 5/325 Image enhancement, e.g. by subtraction techniques using polyenergetic X-rays

Abstract

The invention relates to an X-ray examination apparatus and a method for forming an X-ray image by means of a processing unit (2) for the correction of image data. In order to achieve automatic correction of imaging defects that are caused by imperfections in the imaging and processing chain, the processing unit (2) is succeeded by a defect detection unit (3) for the detection of image defects that can be detected on the basis of image parameters that can be extracted from image data acquired during clinical examinations, and is suitable for adapting processing parameters (15–21) that are used in the processing unit (2) in dependence on the detected image defects. For the detection of image defects that are caused notably by defective sensor elements or pixels of the X-ray detector there is provided a filter unit (37) which forms a defect table for defective sensor elements in dependence on a threshold value; on the basis of such a defect table a correction table (20) is formed in the processing unit (2) in order to be applied to the image data.

Claims

1. An X-ray examination apparatus which includes an X-ray source (11),

an X-ray detector (13) including sensor elements for converting X-ray in electrical charges and a processing unit (2) for the correction of image data and a defect detection unit (3) for the detection of image defects that can be detected on the basis of image parameters that can be extracted from image data arising during clinical examinations and is suitable to adapt, in dependence on the detected image defects, the processing parameters (18–

21) used in the processing unit (2), characterized in that for the detection of image defects caused by defective sensor elements the defect detection unit (3) includes

a filter unit (37) for filtering the image data,

a unit (35) for averaging the filtered image data,

a comparison unit (36) for comparing the filtered and averaged image data with a threshold value in order to form a defect table identifying defective pixels in the image data, and

a processing unit (2) for correcting the defective pixels identified in the defect table by means of a correction table (20) to obtain corrected pixel values and applying the corrected pixel values to the image data from the X-ray detector (13), wherein the correction table (20) is based on a defect table, wherein the defect detection unit (3) calculates a defect table which is compared with the defect table on which the correction table (20) is based, and wherein in the case of a deviation between the two defect tables, the defect table upon which the correction table (20) is based is replaced, as well as the correction table (20) for the correction of defective pixels.

2. An X-ray examination apparatus as claimed in claim 1, characterized in that the defect detection unit (3) is arranged to adapt status parameters of the X-ray examination apparatus.

3. An X-ray examination apparatus as claimed in claim 1, characterized in that continuous detection takes place.

4. An X-ray examination apparatus as claimed in claim 1, characterized in that

the filter unit (37) includes a ranking filter (31) for filtering the image data, an inverter (32) for inverting image data, and

a summing unit (33) for summing the filtered and inverted image data, there also being provided a unit (34) for forming the absolute values of the summed image data.

5. An X-ray examination apparatus as claimed in claim 1, characterized in that

the defect detection unit (3) is arranged to apply a corrected defect table to the processing unit (2) in the case of detection of defective sensor elements.

6. An X-ray examination apparatus as claimed in claim 1, characterized in that

the threshold value is predetermined or can be defined adaptively by forming histograms of the image data subsequent to the unit (34) for forming the absolute value.

7. An X-ray examination apparatus as claimed in claim 4, characterized in that

the ranking filter (31) has variable kernels.

8. A method of forming X-ray images with an X-ray examination apparatus as claimed in claim 1.

9. A computer-readable medium for storing a computer program for the correction of image data comprising the steps of forming a defect table identifying defective pixels, and correcting the defective pixels identified in the defect table by means of a correction table (20) to obtain corrected pixel values, and applying the corrected pixel values to the image data wherein the correction table (20) is based on the defect table, wherein a defect detection unit (3) calculates a defect table which is compared with the defect table on which the correction table (20) is based, and wherein in the case of a deviation between the two defect tables, the defect table upon which the correction table (20) is based is replaced, as well as the correction table (20).