Ambient light suppression using color space information to derive pixel-wise attenuation factors

Patent metadata

Field	Value
Publication number	US-2016366385-A1
Application number	US-201514973406-A
Country	US
Kind code	A1
Filing date	Dec 17, 2015
Priority date	Jun 12, 2015
Publication date	Dec 15, 2016
Grant date	—

Abstract

A method of ambient light suppression in an imaging system, including illuminating leaves of a multi-leaf collimator (MLC) with a first light of a lighting system inside a housing of the MCL, receiving ambient light inside the housing of the MLC through an aperture of the MLC, and capturing, using an imaging system having optics situated inside the housing of the MLC, an image of the leaves of the MLC illuminated with the first light and the ambient light. The method may further include, suppressing the ambient light in the first image to generate a second image of the leaves of the MLC and detecting a feature of the leaves of the MLC in the second image.

First claim

What is claimed is:

1 . A method comprising:
illuminating, with a lighting system disposed inside a housing of a multi-leaf collimator (MLC), leaves of the MLC with a first light; receiving ambient light inside the housing of the MLC through an aperture of the MLC; capturing, using an imaging system having optics situated inside the housing of the MLC, a first image of the leaves of the MLC illuminated with the first light and the ambient light; suppressing, by a processing device, the ambient light in the first image to generate a second image of the leaves of the MLC; and detecting a feature of the leaves of the MLC in the second image.

2 . The method of claim 1 , wherein suppressing ambient light in the first image comprises suppressing ambient light near leading edges of the leaves that shape the aperture of the MCL.

3 . The method of claim 1 , further comprising tracking a position of a leaf of the MLC using the detected feature in the second image.

4 . The method of claim 1 , wherein suppressing the ambient light to generate the second image comprises:
generating an attenuation map for the first image; and generating the second image using the attenuation map.

5 . The method of claim 4 , wherein suppressing the ambient light to generate the second image further comprises determining a saturation map for the first image prior to generating the attenuation map, and wherein generating the attenuation map comprises applying a series of morphological and non-linear transformations to the saturation map.

6 . The method of claim 4 , wherein generating the second image comprises applying the attenuation map to the first image via pixel-wise multiplication.

7 . The method of claim 1 , wherein suppressing the ambient light comprises:
receiving a first image, wherein the first image comprises a first plurality of pixels having a corresponding first plurality of pixel values; generating a second plurality of pixel values by performing a multiplication operation each pixel value of the first plurality of pixel values; and generating a third plurality of pixel values using a polynomial function having coefficients determined to achieve a certain response to saturation levels, wherein the third plurality of pixel values comprises the second image.

8 . The method of claim 4 , wherein the saturation map comprises a distance in color space, in the first image, between a pixel's color and a reference color.

9 . The method of claim 4 , wherein the saturation map is a representation of a color saturation of each pixel in the first image and wherein the method further comprises:
performing a white balancing operation on the first image.

10 . The method of claim 9 , wherein performing the white balancing operation comprises:
determining a region of interest associated with the first image; calculating an average Red Green Blue (RGB) pixel value for each of plurality of pixels associated with the region of interest in the first image; calculating an intensity factor based on the average RGB pixel values; and calculating a white balance parameter vector based on the average RGB pixel values and the intensity factor. applying the white balance parameter vector to a subsequent plurality of pixels, in a subsequent image, corresponding to similar positions of the plurality of pixels in the first image.

11 . The method of claim 10 , wherein the white balance parameter vector is applied by pixel-wise multiplication to correct the plurality of pixels in subsequent images.

12 . The method of claim 4 , wherein generating the attenuation map comprises:
creating an attenuation curve for pixels in the first image, wherein the attenuation curve attenuates pixels with a high saturation value due to ambient light and wherein the attenuation curve does not attenuate pixels that represent a collimator leaf location in the image.

13 . The method of claim 12 , further comprising:
performing a morphological operation on the attenuation map to reduce noise and high frequency artifacts in the attenuation map.

14 . The method of claim 1 , wherein the lighting system is an LED lighting system.

15 . The method of claim 1 , wherein the first light is white light.

16 . The method of claim 1 , wherein the first light has a first primary wavelength and the ambient light has a second primary wavelength, and wherein the first primary wavelength is selected to be dissimilar to the second primary wavelength.

17 . A radiation treatment system comprising:
a multi-leaf collimator (MLC) disposed within a housing; a lighting system, disposed within the housing of the MLC, to illuminate leaves of the MLC with a first light; an imaging system to capture a first image of the leaves of the MLC illuminated with the first light and an ambient light; a memory to store a plurality of images of leaves of the MLC; and a processing device, operatively coupled to the memory, the processing device to:
suppress, by a processing device, the ambient light in the first image to generate a second image of the leaves of the MLC; and
detect a feature of the leaves of the MLC in the second image.

18 . The radiation treatment system of claim 17 , wherein to suppress the ambient light in the first image the processing device is further to suppress ambient light near leading edges of the leaves that shape an aperture of the MLC.

19 . The radiation treatment system of claim 17 , wherein the processing device is further to track a position of a leaf of the MLC using the detected feature with the second image.

20 . The radiation treatment system of claim 19 , wherein the first image comprises a first plurality of pixels having a corresponding first plurality of pixel values and wherein to suppress the ambient light the processing device is further to:
generate a second plurality of pixel values by performing a multiplication operation on each pixel value of the first plurality of pixel values; and generate a third plurality of pixel values using a polynomial function having coefficients determined to obtain a response for a certain type of the ambient light, wherein the third plurality of pixels comprise the second image.

21 . The radiation treatment system of claim 17 , wherein the imaging system comprises optics situated inside the housing of the MLC.

22 . The radiation treatment system of claim 17 , wherein to suppress the ambient light the processing device is further to:
generate an attenuation map for the first image; and generate the second image using the attenuation map.

23 . A non-transitory machine-readable storage medium including instructions that, when accessed by a processing device, cause the processing device to:
receive a first image of leaves of a multi-leaf collimator (MLC) illuminated with a first light and an ambient light; suppress, by the processing device, the ambient light in the first image to generate a second image of the leaves of the MLC; and detect, by the processing device, a feature of the leaves of the MLC in the second image.

24 . The non-transitory machine-readable storage medium of claim 23 , wherein to suppress the ambient light to generate the second image the processing device is further to:
generate an attenuation map for the first image; and generate the second image using the attenuation map.

Assignees

• Accuray Inc

Inventors

• Chappelow Jonathan
• Jordan Petr
• Gao Jian
• Singh Sarbjit
• Laing Trevor
• Maurer Calvin

Classifications

• H04N23/88

  for colour balance, e.g. white-balance circuits or colour temperature control · CPC title

• H04N9/646 Primary

  for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters · CPC title

• H04N9/735

  Electricity · mapped topic

• G06T7/004

  Physics · mapped topic

• A61N5/1045 Primary

  using a multi-leaf collimator, e.g. for intensity modulated radiation therapy or IMRT · CPC title