CROSS REFERENCE TO RELATED APPLICATIONS

This application is related in certain respects to U.S. Pat. No. 8,873,712, issued Oct. 28, 1014, in the name of Wang et al., and entitled EXPOSURE CONTROL USING DIGITAL RADIOGRAPHY DETECTOR, which is hereby incorporated by reference as if fully set forth herein in its entirety.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to radiographic imaging systems, in particular, to radiographic imaging systems using an automatic exposure control (AEC) device.

Scattered radiation is known to degrade image quality in diagnostic x-ray imaging. Traditional methods of reducing scatter include collimation, utilizing an air-gap, and/or utilizing an anti-scatter grid. Best practices in radiography prescribe collimation on every exam and, while this is helpful, it is not completely sufficient due to scatter that occurs within the subject. Likewise, air-gap techniques are helpful, but are not practical at the bedside. Anti-scatter grids are the most popular means of reducing x-ray scatter in portable imaging, but they present challenges to radiographers such as positioning and alignment. Image processing tools, such as SmartGrid from Carestream Health, Inc., have been developed to compensate for the effects of x-ray scatter in a radiographic image, and produces results comparable to those of a physical anti-scatter grid. The SmartGrid algorithm estimates the scatter distribution and removes it from the radiographic image, resulting in an image with improved contrast. Many physical factors affect scatter: the energy spectrum of the x-ray beam, thickness and material composition of the subject being imaged, and collimation, for example. The SmartGrid algorithm accommodates these variables automatically and so its use results in image quality that approximates anti-scatter grid visual performance.

A scatter removal algorithm is an enhancement algorithm that improves radiographic image contrast by suppressing scatter in the image. The fundamental method includes developing a scatter distribution image, which is a representation of the scatter contained in the radiographic image, and then subtracting it from the original input image. The scatter distribution image is developed using information from the image in both linear exposure space as well as attenuation space, which is a log transformation of the linear data. Segmentation is done to focus the development of the scatter field on relevant anatomical data and is used to compute the mean linear exposure of the input image. Parameters used to estimate scatter are determined. These include the scatter-to-primary ratio (SPR) and a curvature parameter used to control perturbation of the scatter distribution as the scatter field is developed. The scatter distribution image is computed based upon the default assumption that every object exposed by x-rays has a basic (default) scatter distribution that is characterized by a certain level of energy and scatter intensity variation across the whole object field of view. Adaptive updating of the scatter intensity across the entire object field of view is performed in a repetitive fashion based upon the SPR parameter for a prescribed number of iterations.

The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE INVENTION

Scatter removal processing has demonstrated that equivalent radiographic image quality can be achieved without using an anti-scatter grid at a dose level comparable to that when an anti-scatter grid is used. Compensating the anti-scatter grid bucky factor can be easily performed with portable imaging where the exposure level is determined manually by the operator. However, for a radiographic system with AEC, the exposure level of the detector to the x-ray beam is preconfigured generically by programming an AEC trigger level. When a radiographic image is captured without an anti-scatter grid the AEC will be triggered more quickly, as compared to the same exposure with an anti-scatter grid, at a lower x-ray exposure level to the subject. This automatically applied lower exposure level to the subject does not allow a scatter removal algorithm to fully realize its benefit. To overcome this issue, whenever a scatter removal algorithm is to be used, either without a grid or with a low ratio grid, the AEC will be preconfigured at a higher trigger level to ensure enough primary exposure is delivered to the subject as if a high ratio grid is used in the x-ray beam path.

A radiographic imaging system uses an automatic exposure control device configured at a default shut-off threshold. If the radiographic imaging system includes a processor programmed to process the image by executing a scatter removal algorithm thereupon, the shut-off threshold of the AEC is increased prior to capturing the radiographic image.

In one embodiment, a radiographic imaging system includes an x-ray source, an x-ray detector, and an automatic exposure control (AEC) device coupled to the x-ray source. The AEC is configured to trigger a shutdown of the x-ray source when the AEC receives an amount of x-ray energy that satisfies a preset threshold. A processing system may receive a request to execute a program for removing x-ray scatter in the captured radiographic image and, in response, the processing system increases the preset threshold for triggering the AEC.

In another embodiment, a method of capturing and processing a radiographic image of a subject includes positioning an x-ray source and an x-ray detector about a subject to be radiographically imaged. A default threshold is preset in an AEC device configured to terminate x-ray emission from the x-ray source. In response to a request for using a scatter removal algorithm, the preset default threshold of the AEC is increased prior to capturing the radiographic image of the subject.

In another embodiment, a method of using an AEC in a radiographic imaging system includes providing an AEC having a programmed default shut-off threshold. After determining that the radiographic imaging system is configured to process images captured by the radiographic imaging system to remove scatter radiation effects, the shut-off threshold of the AEC is increased prior to capturing the radiographic image of the subject.

The summary descriptions above are not meant to describe individual separate embodiments whose elements are not interchangeable. In fact, many of the elements described as related to a particular embodiment can be used together with, and possibly interchanged with, elements of other described embodiments. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

This brief description of the invention is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments, and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention, which is defined only by the appended claims. This brief description is provided to introduce an illustrative selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.

