Methods and systems for reducing bright burn in images
A system and method to reduce bright burn in images, such as x-ray images. The reduction of bright burn may be accomplished by processing a received raw image to obtain a grey-value histogram. The raw image may be divided into a plurality of regions of interest, and an average signal of each region of interest is calculated. Regions of interest are identified as bright burn candidates based on a predetermined function of the average signal of each region of interest and the grey-value histogram of the entire raw image. The regions of interest may be analyzed for local connectivity to estimate bright burn areas. An image with reduced bright burn is generated by either automatically adjusting a physical wedge filter position based on the bright burn areas, or by adaptively reducing a signal level of the bright burn areas.
1. A method for reducing bright burn in an image, comprising:
accessing image data;
determining a grey value distribution of the image data;
identifying one or more regions of the image data;
determining a magnitude of an average signal for each of the regions;
identifying one or more of the regions as bright burn regions by comparing the magnitude of the average signal of each region with a predetermined function of the grey value distribution of the image data; and
automatically filtering a signal of the identified bright burn regions exclusive of filtering non-bright burn regions of the image to reduce bright burn in the bright burn regions.
2. The method according to claim 1 , further comprising:
evaluating a value of the predetermined function of the grey value distribution;
comparing the magnitude of the average signal of each region to the value of the predetermined function of the grey value distribution; and
identifying one or more of the regions as bright burn regions when the magnitude of the average signal of a region exceeds the value of the predetermined function of the grey value distribution of the image data wherein the predetermined function of the grey value distribution of the image data is a whole image histogram of the image data.
3. The method according to claim 2 , wherein the predetermined function uses a predetermined number multiplied by approximately one-half of a median value of the grey value distribution.
4. The method according to claim 2 , wherein the predetermined function uses the greater of approximately 0.80 of a median of the grey value distribution and a predetermined number multiplied by a median value of the grey value distribution.
5. The method according to claim 2 , wherein the predetermined function uses a predetermined percentage of a dynamic range of the grey value distribution.
6. The method according to claim 1 , further comprising:
determining whether one or more bright burn regions are locally connected;
establishing an aggregate bright burn area as a function of locally connected bright burn regions; and
reducing bright burn in the aggregate bright burn area.
7. The method according to claim 6 , wherein the step of automatically filtering a signal further comprises:
moving a wedge filter to attenuate signal in the bright burn regions.
8. The method according to claim 6 , wherein the step of automatically filtering a signal further comprises:
adjusting a physical filter position to attenuate signal associated with the bright burn regions as a function of the aggregate bright burn region area.
9. The method according to claim 8 , wherein said adjusting step is performed independent of intervention of a human operator.
10. The method according to claim 1 , wherein the step of automatically filtering a signal further comprises:
subtracting coarse grey value signal content representing the identified bright burn regions from signal content of the identified bright burn regions.
11. The method according to claim 10 , wherein the subtracting includes subtracting a large kernel low pass filter from the one or more bright burn regions.
12. The method according to claim 1 , wherein said grey value distribution is a histogram.
13. The method according to claim 1 , wherein said one or more regions of the image data and said one or more bright burn regions are connected subsets of pixels of the entire image.
14. The method according to claim 1 , further comprising:
accessing the image data from an x-ray detector.
15. An apparatus for reducing bright burn in an image, comprising:
means for accessing image data;
means for determining a grey value distribution of the image data;
means for identifying one or more regions of the image data;
means for determining a magnitude of an average signal for each of the regions;
means for identifying one or more of the regions as bright burn regions by comparing the magnitude of the average signal of each region with a predetermined function of the grey value distribution of the image data; and
means for automatically filtering a signal of the identified bright burn regions exclusive of filtering non-bright burn regions of the image to reduce bright burn characteristics in the bright burn regions by adjusting a physical filter position to attenuate signal associated with the bright burn regions as a function of the aggregate bright burn region area.
16. The apparatus according to claim 15 , further comprising:
means for evaluating a value of the predetermine function of the grey value distribution;
means for comparing the magnitude of the average signal of each region to the value of the predetermined function of the grey value distribution; and
means for identifying one or more of the regions as bright burn regions when the magnitude of the average signal of a region exceeds the value of the predetermined function of the grey value distribution of the image data wherein the predetermined function of the grey value distribution of the image data is a whole image histogram of the image data.
17. The apparatus according to claim 16 , wherein the predetermined function uses a predetermined number multiplied by approximately one-half of a median value of the grey value distribution.
18. The apparatus according to claim 16 , wherein the predetermined function uses the greater of approximately 0.80 of a median of the grey value distribution and a predetermined number multiplied by a median value of the grey value distribution.
19. The apparatus according to claim 16 , wherein the predetermined function uses a predetermined percentage of a dynamic range of the grey value distribution.
20. The apparatus according to claim 15 , further comprising:
means for determining whether one or more bright burn regions are locally connected;
means for establishing an aggregate bright burn area as a function of locally connected bright burn regions; and
means for reducing bright burn in the aggregate bright burn area.
21. The apparatus according to claim 20 , further comprising:
means for moving a wedge filter in adjusting said physical filter position.
22. The apparatus according to claim 20 , further comprising:
means for subtracting signal content in an adaptive manner from the identified bright burn regions.
23. The apparatus according to claim 15 , further comprising:
means for subtracting coarse grey value signal content representing the identified bright burn regions from signal content of the identified bright burn regions.
24. The apparatus according to claim 23 , wherein the subtracting includes subtracting a large kernel low pass filter from the one or more bright burn regions.
25. The apparatus according to claim 15 , wherein said grey value distribution is a histogram.
26. The apparatus according to claim 15 , wherein the one or more regions of the image data and the one or more bright burn regions are connected subsets of pixels of the entire image.
27. The apparatus according to claim 15 , further comprising:
means for accessing the image data from an x-ray detector.
28. A system for reducing bright burn characteristics in image data, comprising:
at least one memory;
at least one processor, coupled to the at least one memory, the at least one processor adapted to execute code that performs the steps of:
accessing image data;
determining a grey value distribution of the image data;
identifying one or more regions of the image data;
determining a magnitude of an average signal for each of the regions;
identifying one or more of the regions as bright burn regions by comparing the magnitude of the average signal of each region with a predetermined function of the grey value distribution of the image data; and
automatically filtering a signal of the identified bright burn regions exclusive of filtering non-bright burn regions of the image by subtracting coarse grey value signal content representing the identified bright burn regions from signal content of the identified bright burn regions.
29. A method for reducing bright burn in an imaging system, comprising:
processing an image to obtain a grey-value histogram;
dividing the image into a plurality of regions of interest, said regions of interest representing a connected subset of pixels of the entire image;
calculating an average signal of each region of interest;
identifying regions of interest as bright burn candidates by comparing a function of the average signal of each region of interest with the grey-value histogram of the entire image;
analyzing the regions of interest identified as bright burn candidates for local connectivity to estimate bright burn areas; and
automatically filtering a signal of the identified bright burn regions exclusive of filtering non-bright burn regions of the image by adjusting a wedge filter position.