X-ray diagnostic apparatus and method for operating an x-ray diagnostic apparatus for determining quality values

• US 20060126911A1
• Filed: 12/02/2005
• Published: 06/15/2006
• Est. Priority Date: 12/13/2004
• Status: Active Grant

• Current Assignee: Siemens Healthcare GMBH (Siemens AG)
• Original Assignee: Siemens AG
• Inventors: Heer, Volker, Durlak, Peter, Bohm, Stefan, Kolarjk, Martin
• Granted Patent: US 7,539,336 B2
• Time in Patent Office: Days
• US Class Current: 382/132
• CPC Class Codes: A61B 6/504 for diagnosis of blood vessels, e.g. by angiography
• CPC Class Codes: A61B 6/583 using calibration phantoms
• CPC Class Codes: G06T 7/0002 Inspection of images, e.g. flaw detection
• CPC Class Codes: H04N 5/325 Image enhancement, e.g. by subtraction techniques using polyenergetic X-rays
• CPC Class Codes: Y10S 128/922 including image analysis

Abstract

The invention relates to an angiographic x-ray diagnostic apparatus with an x-ray radiator having an x-ray tube, with a patient positioning table having a radiation-transparent positioning plate and mattress, with an x-ray detector, with an imaging system, an image processing unit and a measuring device to which the output signals of the x-ray detector are fed and which has a first device for determining a value determining the reproduction quality of clinically relevant objects, a second device for determining local variances of the noise in a homogenous image region of different x-ray images and a device for taking the ratio of the output values of the two devices.

Claims

1-17. -17. (canceled)

18. Angiographic x-ray diagnostic apparatus, comprising:

an x-ray radiator including an x-ray tube;

a patient positioning table including a radiation-transparent positioning plate and mattress;

an x-ray detector;

an imaging system;

an image processing unit; and

a measuring device connected to the x-ray detector for acquiring output signals of the x-ray detector, the measuring device comprising;

a first device for determining a quality value related to a reproduction quality of a clinically relevant object;

a second device configured to calculate a local variance of a noise present in a homogenous image region of different x-ray images; and

a calculation device for calculating a ratio of the quality value and the local variance of noise.

19. The x-ray diagnostic apparatus as claimed in claim 18, wherein the first device further includes a prediction stage for predicting a position of the clinically relevant object.

20. The x-ray diagnostic apparatus as claimed in claim 18, wherein the first device further includes a lookup table containing a-priori knowledge related to the shape of the clinically relevant object.

21. The x-ray diagnostic apparatus as claimed in claim 18, wherein the first device further includes a subtraction stage for calculating a difference between a current image extracted from a series of continuous images and a background image.

22. The x-ray diagnostic apparatus as claimed in claim 19, wherein the quality value is calculated based on an output signal of the prediction stage.

23. The x-ray diagnostic apparatus as claimed in claim 20, wherein the quality value is calculated based on an output signal of the lookup table.

24. The x-ray diagnostic apparatus as claimed in claim 21, wherein the quality value is calculated based on an output signal of the subtraction stage.

25. The x-ray diagnostic apparatus as claimed in claim 18, wherein the local variance of the noise is calculated using a background image.

26. The x-ray diagnostic apparatus as claimed in claim 18, wherein the local variance of the noise is calculated using a current image of continuous current images.

27. The x-ray diagnostic apparatus as claimed in claim 18, further comprising an adding unit for determining a sum of first and second local variances of noise, the first variance calculated using a background image, and the second local variance calculated using a current image of continuous current images.

28. The x-ray diagnostic apparatus as claimed in claim 19, wherein the first device comprises a Hough transformation device connected to the prediction stage.

29. The x-ray diagnostic apparatus as claimed in claim 20, wherein the first device comprises a Hough transformation device connected to the lookup table.

30. The x-ray diagnostic apparatus as claimed in claim 21, wherein the first device comprises a Hough transformation device connected to the subtraction stage.

31. The x-ray diagnostic apparatus as claimed in claim 19, wherein the local variance is calculated based on an output signal of the prediction stage.

32. The x-ray diagnostic apparatus as claimed in claim 20, wherein the local variance is calculated based on an output signal of the lookup table.

33. The x-ray diagnostic apparatus as claimed in claim 21, wherein the local variance is calculated based on an output signal of the subtraction stage.

34. The x-ray diagnostic apparatus as claimed in claim 18, wherein the x-ray radiator comprises a multi-leaf diaphragm having a collimator unit or a pre-filtering unit.

35. The x-ray diagnostic apparatus as claimed in claim 18, further comprising an anti-scatter grid assigned to the x-ray detector.

36. The x-ray diagnostic apparatus as claimed in claim 18, wherein the clinically relevant object is a guide wire, a catheter or a stent.

37. A measuring method for checking an x-ray diagnostic apparatus, the method comprising:

digitally acquiring fluoroscopic series of x-ray images of a technical phantom and storing the acquired digital data;

calculating a difference between a dynamic image and a background image;

predicting a measuring field;

determining a-priori information about the shape of a clinically relevant object;

applying a Hough transformation on a gray value image corresponding to the difference;

determining a contrast of the clinically relevant object from the Hough-transformed gray value image;

calculating a square of the determined contrast;

calculating a noise variance by determining a sum of a noise variance of a homogenous image region and a variance of the background image;

determining a contrast-to-noise ratio of the determined contrast and the calculated noise variance;

dynamically averaging a square of the contrast-to-noise ratio; and

determining a Clinical Relevant Fluoroscopy Performance (CRFP) index for the x-ray diagnostic apparatus.

38. The measuring method for checking an x-ray diagnostic apparatus, the method comprising:

digitally acquiring fluoroscopic series of x-ray images of a technical phantom and storing the acquired digital data;

calculating a difference between a dynamic image and a background image;

predicting a Region of Interest (ROI);

determining a-priori information about the shape of a clinically relevant object;

determining a variance of the clinically relevant object based on a gray value image corresponding to the calculated difference,

calculating a noise variance by determining a sum of a noise variance of a homogeneous image region and the variance of the background image;

determining a ratio of the noise variance and the variance of the background image;

dynamically averaging the determined ratio; and

determining a Clinical Relevant Fluoroscopy Performance (CRFP) index for the x-ray diagnostic apparatuses.

39. A measuring method for checking a clinically relevant object using a standardized x-ray diagnostic apparatus, the method comprising:

digitally acquiring fluoroscopic series of x-ray images of the clinically relevant object and storing the acquired digital data by the standardized x-ray diagnostic apparatus;

calculating a difference between a dynamic image and a background image;

predicting a measuring field;

determining a-priori information about the shape of the clinically relevant object;

applying a Hough transformation on a gray value image of the calculated difference;

determining a contrast of the clinically relevant object from the Hough-transformed gray value image;

calculating a square of the determined contrast;

calculating a noise variance by determining a sum of a noise variance of a homogeneous image region and a variance of the background image;

determining a contrast-to-noise ratio of the determined contrast and the calculated noise variance;

dynamically averaging a square of the contrast-to-noise ratio; and

determining a Clinical Relevant Fluoroscopy Performance (CRFP) index for the clinically relevant object.

40. A measuring method for checking a clinically relevant object using a standardized x-ray diagnostic apparatus, the method comprising:

digitally acquiring fluoroscopic series of x-ray images of the clinically relevant object and storing the acquired digital data by the standardized x-ray diagnostic apparatus;

calculating a difference between a dynamic image and a background image;

predicting a Region of Interest (ROI);

determining a-priori information about the shape of the clinically relevant object;

determining a variance of the clinically relevant object using a gray value image corresponding to the calculated difference;

calculating a noise variance by determining a sum of a noise variance of a homogeneous image region and a variance of the background image;

determining a ratio of the noise variance and the variance of the background image;

dynamically averaging the determined ratio; and

determining a Clinical Relevant Fluoroscopy Performance (CRFP) index for the clinically relevant object.