# US 2016/0366385 A1 · Ambient light suppression using color space information to derive pixel-wise attenuation factors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2016/0366385 A1 - Document ID: US20160366385A1 - Status: Published application - Kind: A1 - Application number: 14/973,406 - Filed: 2015-12-17 - Published: 2016-12-15 - Earliest claimed: 2015-06-12 - Assignees: Accuray Incorporated - Applicants: Accuray Incorporated - Inventors: Jonathan Chappelow; Petr Jordan; Jian Gao; Sarbjit Singh; Trevor Laing; Calvin Maurer - Web page: https://patentgrep.com/patent/US20160366385A1 ## CPC - H04N 9/646: {for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters} - A61B 6/50: specially adapted for specific body parts; specially adapted for specific clinical applications - A61N 5/1045: {using a multi-leaf collimator, e.g. for intensity modulated radiation therapy or IMRT} - G06T 5/30: Erosion or dilatation, e.g. thinning - G06T 5/70: Denoising; Smoothing - G06T 5/90: Dynamic range modification of images or parts thereof - G06T 7/13: Edge detection - G06T 7/70: Determining position or orientation of objects or cameras (camera calibration G06T7/80) - G06T 7/90: Determination of colour characteristics - G21K 1/046: {varying the contour of the field, e.g. multileaf collimators} - H04N 23/88: for colour balance, e.g. white-balance circuits or colour temperature control - A61B 6/022: {Stereoscopic imaging} - A61B 6/032: {Transmission computed tomography [CT]} - A61N 5/1049: {for verifying the position of the patient with respect to the radiation beam} - A61N 5/1081: {Rotating beam systems with a specific mechanical construction, e.g. gantries} - A61N 5/1083: {Robot arm beam systems} - A61N 2005/1061: {using an x-ray imaging system having a separate imaging source} - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - A61N: ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY (measurement of bioelectric currents A61B; surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body A61B18/00; anaesthetic apparatus in general A61M; incandescent lamps H01K; infrared radiators for heating H05B) - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - G21K: HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES ## 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. ## Claims ### Claim 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. ### Claim 2 (depends on 1) 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. ### Claim 3 (depends on 1) The method of claim 1, further comprising tracking a position of a leaf of the MLC using the detected feature in the second image. ### Claim 4 (depends on 1) 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. ### Claim 5 (depends on 4) 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. ### Claim 6 (depends on 4) The method of claim 4, wherein generating the second image comprises applying the attenuation map to the first image via pixel-wise multiplication. ### Claim 7 (depends on 1) 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. ### Claim 8 (depends on 4) 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. ### Claim 9 (depends on 4) 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. ### Claim 10 (depends on 9) 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. ### Claim 11 (depends on 10) 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. ### Claim 12 (depends on 4) 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. ### Claim 13 (depends on 12) 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. ### Claim 14 (depends on 1) The method of claim 1, wherein the lighting system is an LED lighting system. ### Claim 15 (depends on 1) The method of claim 1, wherein the first light is white light. ### Claim 16 (depends on 1) 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. ### Claim 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. ### Claim 18 (depends on 17) 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. ### Claim 19 (depends on 17) 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. ### Claim 20 (depends on 19) 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. ### Claim 21 (depends on 17) The radiation treatment system of claim 17, wherein the imaging system comprises optics situated inside the housing of the MLC. ### Claim 22 (depends on 17) 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. ### Claim 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. ### Claim 24 (depends on 23) 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.