FIELD

This patent specification pertains to x-ray mammography and tomosynthesis, and more specifically to techniques and equipment for acquiring and/or synthesizing, processing, storing and displaying mammograms, tomosynthesis projection images, synthesized two-dimensional (2D) images and/or tomosynthesis reconstructed images, and to medical image softcopy reading systems, to hanging protocols and to other medical image display features.

BACKGROUND

Mammography has long been used to screen for breast cancer and other abnormalities and for diagnostics. Traditionally, mammograms were formed on X-ray film, but more recently flat panel digital imagers have been introduced that acquire a mammogram in digital form and thereby facilitate analysis and storage and provide other benefits as well. Further, substantial attention and technological development has been dedicated towards obtaining a three-dimensional image of the breast, using methods such as breast tomosynthesis. In contrast to the 2D images generated by legacy mammography systems, breast tomosynthesis systems construct a 3D image volume from a series of 2D projection images, each projection image obtained at a different angular displacement of the x-ray source relative to the image detector as the x-ray source is scanned over the detector. The constructed 3D image volume is typically presented as a plurality of slabs or slices of image data, the slabs geometrically reconstructed on planes parallel to the imaging detector. The reconstructed tomosynthesis slices reduce or eliminate the problems caused by tissue overlap and structure noise in single slice two-dimensional mammography imaging by permitting a radiologist to scroll through the slabs and view underlying structures.

Tomosynthesis systems have recently approved for breast cancer screening and diagnosis. The assignee of this patent specification, Hologic, Inc., has demonstrated at trade shows in this country a fused, multimode mammography/tomosynthesis system that takes either or both types of mammogram and tomosynthesis images, either while the breast remains immobilized or in different compressions of the breast. Other companies have proposed the introduction of systems which are dedicated to tomosynthesis imaging, i.e., which do not include the ability to also acquire a mammogram.

Restricting systems to tomosynthesis acquisition and image display may present an obstacle to acceptance of the tomosynthesis imaging technology, as medical professionals have grown accustomed to screening and analysis of mammogram images. Mammograms offer good visualization of micro-calcifications, and can offer higher spatial resolution when compared with tomosynthesis images. While tomosynthesis images provided by dedicated breast tomosynthesis systems in the art have other desirable characteristics (i.e., better visualization of structures), such systems do not leverage the existing interpretation expertise of medical professionals.

One method of leveraging existing medical expertise to facilitate the transition to tomosynthesis technology was described in U.S. Pat. No. 7,760,924, entitled “System and Method for Generating a 2D Image from a Tomosynthesis Data Set.” The '924 patent describes a method of generating a synthesized 2D image which may be displayed along with tomosynthesis projection or reconstructed images, to assist in screening and diagnosis.

SUMMARY

According to one aspect of the invention, it is realized that an improved synthesized 2D image may be obtained by merging the most relevant data from a plurality of data sources. In one embodiment, the merging is performed using a combination of 2D and 3D image data, wherein the 2D image may include either an acquired mammogram, a synthesized mammogram, or a tomosynthesis projection image, and the 3D image data may comprises a reconstructed 3D data set. In an alternate embodiment, the merged data is formed using 3D projection images and/or reconstruction images. The improved synthesized image, referred to herein as a ‘merged’ image IMERGE, incorporates the most relevant information from all acquired and computer generated data sets into one ‘supreme’ 2D image for display on a workstation. Thus, regions of pixels in the displayed merged image may be sourced by different images in a data set including but not limited to one or more of an acquired 2D image (mammogram or tomosynthesis projection image), a synthesized 2D image, or a reconstructed tomosynthesis slice or slab. The particular regions may be identified statically (i.e., within a particular grid), or dynamically, and may range in granularity from one pixel to all pixels in the image. With such an arrangement, the radiologist may quickly view a large number of regions of interest within a breast while referencing only a single 2D image, thereby increasing the performance and efficiency of breast cancer screening and diagnosis.

According to a further aspect of the invention, a map is automatically generated for each region in the merged image, identifying the particular image that sourced the region in the merged image. An interface feature may be provided that enables the origin source image to be displayed when the region is selected by the user. The origin source image may be displayed in a variety of manners, e.g., overlaid over the merged image to allow toggling between the two images or display using cine mode, or displayed adjacent to the merged image, etc.

According to a further aspect of the invention, it is determined that particular types of images may include different types of relevant information. For example, calcifications are best visualized in 2D mammograms, while masses are best visualized using 3D reconstructed images. In one embodiment, different filters are applied to each of the different types of images (i.e., 2D and 3D), where the filters are selected to highlight the particular characteristics of the images which are best displayed in the respective imaging mode. Appropriate filtering of the respective types of images prior to the merge ensures that the final merged image includes the most relevant information that can be obtained from all image types. Alternatively, the type of filtering that is performed for the various images may be defined via user input, which permits a user to select a ‘merge mode’, for example, geared towards highlighting masses, calcifications, or making the merged image appear to be a particular image type, such as a 3D reconstructed slice, or a 2D mammogram.

Merging of the images may be done in a variety of ways. According to one embodiment, general purpose Computer Assisted Diagnosis (CAD) algorithms are used to identify features within each of the 2D and 3D images. The various features are assigned weights, and the merged image is built by selecting the image having the region with the most significant weight. The size of the region may vary in granularity from one pixel to many (or even all) pixels, and may be statically pre-defined, or may have margins which vary in accordance with the varying thresholds of the source images.

In accordance with a further aspect of the invention, it is envisioned that the merged image may be pre-processed and stored following tomosynthesis acquisition, or dynamically generated in response to a request for a merged image at a radiologist work station.

It is realized that the visualization of such a merged image may have some drawbacks. For example, there may be neighboring regions in the merged image which exhibit bright calcifications but in fact are sourced from image slices which are distant from one another in the z-plane. Therefore, what may appear to as a mass of calcifications in the merged image may, in fact, be calcifications which are distributed throughout the breast and thus do not actually represent a calc cluster that requires further review. According to a further aspect of the invention, this problem is overcome by the inclusion of a cluster spread indicator. The cluster spread indicator is a graphical indicator provided with the merged image, and visually indicates the distribution of calcifications along the z-plane, allowing the medical professional to quickly assess whether a group of calcifications comprise a calcification cluster.

One aspect of the invention includes a method including the steps of obtaining a plurality of images, each of the images in the plurality having at least one corresponding region, generating a merged image, the merged image also having the corresponding region, the step of generating including: selecting an image source from the plurality of images to source image data for the corresponding region in the merged image by comparing attributes of the corresponding regions of the plurality of images to identify the image source having preferred attributes.

The foregoing aspect can include any one or more of the following embodiments. The preferred attributes includes attributes indicative of regions of interest, such as cancers, or alternatively such as more accurate representation of breast density or breast anatomy (e.g. truthful breast-border/nipple appearance). In general, any attribute capable of delivering a high/better-quality image can be relevant here. The method can further include filtering the plurality of images to magnify attributes of the plurality of images. The filtering can apply different filters to images of different types. The method can further include visually indicating a distribution of the preferred attributes in the corresponding region by providing a histogram to illustrate a depth of the preferred attributes. The plurality of images can comprise a 2D image and a 3D image. The plurality of images can be selected from a group consisting of tomosynthesis projection images, reconstructed tomosynthesis slices, mammograms, and synthesized two dimensional images. The method can further include generating a map for a region in the merged image, whereby the map identifies at least one of the plurality of images that sourced the region in the merged image. The method can further include displaying the at least one of the plurality of images that sourced the region when the region is selected by a user. The at least one of the plurality of images that sourced the region can overlay the merged image such that a user can view both types of images at the same time or by toggling between the types.

According to another aspect of the invention, a display workstation comprises an interface, the interface including a mechanism which, upon selection, results in the generation and/or display of a merged image, the merged image comprising a two dimensional synthesized image comprising a plurality of regions, wherein at least two of the regions are sourced by different images selected from a group of images, and wherein the group of images include tomosynthesis projection images, tomosynthesis reconstruction slices, mammograms and synthesized 2D images.

The foregoing aspect can include any one or more of the following embodiments. The interface can further include a mode selection mechanism enabling a user to select a mode of either generation or display of the merged image. The interface can further include a mechanism for selecting a region of the merged image and a mechanism for displaying three-dimensional information related to the selected region on a display station. Additionally or alternatively, the generation of the merged display does not take place at the workstation, but can happen in another part of the system. The interface can display a map for at least one of the plurality of regions in the merged image such that a user can select at least one of the plurality of regions to display one of the group of images that sourced the at least one of the plurality of regions. The interface can allow a user to view both of or toggle between the merged image and the one of the group of images that sourced the at least one of the plurality of regions. The interface can provide a graphical indicator along with a display of the merged image such that the graphical indicator illustrates a depth of attributes within the regions. The interface can display simultaneously, sequentially, or in toggle mode two or more of the merged image, the tomosynthesis projection image, the tomosynthesis reconstruction slice, the mammogram and the synthesized 2D image.

The present invention can include any one or more of the foregoing aspects and/or embodiments, in any combination, and can include any one or more of any of the details described herein.

These and other aspects of the invention will be described in more detail with regard to the below figures.

