Abstract:
One or more systems and/or techniques are described for generating volumetric data from both radiographic and ultrasound examinations of an object, where the radiographic volumetric data and the ultrasound volumetric data are representative of a substantially same volumetric space of the object. This allows, for example, corresponding portions of the volumetric data and/or images resulting therefrom (e.g., indicative of a tumor) to be identified for comparison via the different modalities. Moreover, in one embodiment, a compression paddle of a mammography examination apparatus is configured to selectively receive an ultrasound component.

Description:
RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/345,080, filed on Dec. 29, 2008, entitled “MULTI-MODALITY IMAGE ACQUISITION”. 
     
    
     BACKGROUND 
       [0002]    The present application relates to the examination of objects using different image acquisition modalities. It finds particular application to the use of ultrasound and x-rays in mammography examinations. It also relates to medical and other applications where information from multiple imaging modalities can be used to provide additional information about the structure and/or function of an object. 
         [0003]    X-ray devices, in general, generate one or more 2-D images of an object under examination. The object is exposed to radiation, and an image is formed based upon the radiation absorbed by the object, or rather an amount of radiation that is able to pass through the object. Highly dense objects absorb more radiation than less dense objects, and thus an object having a higher density, such as a bone or mass, for example, will be apparent when surrounded by less dense objects, such as fat tissue or muscle. 
         [0004]    In medical systems, x-ray devices are commonly used to detect broken bones, masses, calcium deposits, etc. that are not visible to the naked eye. One type of x-ray device is a mammography unit that generally comprises an x-ray tube, two compression paddles, and a detector array. The detector array and one compression paddle are mounted on a diametrically opposing side of the breast tissue (e.g., the object under examination) from the x-ray tube and the second compression paddle. The x-ray tube emits x-rays, and the x-rays traverse the breast tissue, while it is compressed between the two paddles. X-rays that traverse the breast tissue are detected by the detector array. In digital radiology, digital detectors (of the detector array) detect the x-rays, and reconstruction algorithms are used to create one or more two-dimensional (2-D) images of the breast tissue in the latitudinal dimension (e.g., orthogonal to a center x-ray beam and/or parallel to the detector array). 
         [0005]    While 2-D x-ray images are useful in mammography and other applications, these images provide little or no resolution in the longitudinal direction (e.g., parallel to the x-ray beam and/or orthogonal to the detector plane formed by the detectors). On a breast examination, for example, a 2-D image cannot provide information about whether a mass is nearer the x-ray tube or the detector array. A less dense, but potentially cancerous mass, for example, may be masked by a more dense target, such as scar tissue, if the mass and scar tissue have a similar latitudinal coordinate (e.g., one target is on top of the other). Additionally, many (e.g., 85 percent in breast cancer screenings) positive findings are false positives (e.g., are not related to breast cancer). Therefore, patients are ordinarily called back for further testing if a positive finding is detected. 
         [0006]    Ultrasound imaging is one common method used to confirm or reject an initial positive finding. Typically, an ultrasound probe transmits high-frequency sound waves (e.g., pulses) into the object under examination. As the sound waves travel through the object, some of the sound waves interact with a more dense target (e.g., mass, scar tissue, etc.), for example, that reflects a larger number of sound waves and/or causes a more significant attenuation of the sound waves (relative to less dense targets within the object). The sound waves that are reflected (e.g., echoes) are detected by the probe, and an ultrasound device calculates the distance from the probe to the more dense object and/or the intensity of the echoes. An image of the target inside the breast is formed based upon the calculations. 
         [0007]    While current cancer screening techniques have proven effective for detecting early signs of cancer in some situations, there remains room for improvement. The x-ray scanning and ultrasound imaging are typically done at different times and in different physical positions. For example, in breast cancer screening, the mammography exam is usually done with a woman standing up and the breast tissue in a compressed state, while the ultrasound exam is done with the woman flat on her back and the breast stretched out (e.g., to reduce the distance the sound wave has to travel in the breast, thereby improving the image quality). Therefore, it is difficult to compare the images and detect similar details in the x-ray and the ultrasound images. Additionally, initial false positives can generate feelings of anxiety or distress that can last well after the ultrasound confirms that the initial positive finding was false. 
       SUMMARY 
       [0008]    Aspects of the present application address the above matters, and others. According to one aspect, a method is provided. The method comprises acquiring volumetric data of an object under examination from a radiographic examination of the object. The method also comprises acquiring volumetric data of the object under examination from an ultrasound examination of the object, the volumetric data acquired from the radiographic examination and the volumetric data acquired from the ultrasound examination at least partially representative of a substantially same volumetric space of the object. 
         [0009]    According to another aspect, a mammography examination apparatus is provided. The apparatus comprises an x-ray source configured to emit x-rays into an examination region of the mammography examination apparatus during a radiographic examination of a breast in the examination region. The apparatus also comprises an x-ray detector configured to detect emitted x-rays that traverse the examination region. The apparatus further comprises an ultrasound component configured to emit ultrasound waves into the examination region of the mammography examination apparatus during an ultrasound examination of the breast and to detect ultrasound waves that have at least partially traversed the examination region. 
         [0010]    According to yet another aspect, a method is provided. The method comprises correlating, with a spatial registration component, a portion of an x-ray image of an object under examination with a portion of an ultrasound image of the object under examination, the x-ray image and the ultrasound image substantially representing a same volumetric space of the object under examination. 
         [0011]    According to yet another aspect, an apparatus for use with a mammography system is provided. The apparatus comprises a compression paddle configured to immobilize a breast under examination, the compression paddle configured to selectively receive an ultrasound component. 
         [0012]    Those of ordinary skill in the art will appreciate still other aspects of the present application upon reading and understanding the appended description. 
     
    
     
       FIGURES 
         [0013]    The application is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which: 
           [0014]      FIG. 1  is a schematic block diagram illustrating a scanner wherein x-ray and ultrasound data may be acquired. 
           [0015]      FIG. 2  illustrates example scanning planes of an object that may be acquired. 
           [0016]      FIG. 3  illustrates a cross-sectional area of an object scanning apparatus wherein x-ray and ultrasound data may be acquired. 
           [0017]      FIG. 4  illustrates a cross-sectional area of an ultrasound component comprising a plurality of transducers. 
           [0018]      FIG. 5  illustrates a cross-sectional area of an object scanning apparatus wherein x-ray and ultrasound data may be acquired. 
           [0019]      FIG. 6  is a flow diagram illustrating an example method of acquiring data from two scanning modalities. 
           [0020]      FIG. 7  is a flow diagram illustrating an example method of acquiring data for spatial registration. 
       
    
    
     DESCRIPTION 
       [0021]      FIG. 1  depicts an example scanner  100 . The scanner  100  may be used to scan tissue (e.g., a breast) at a medical center, for example. As illustrated, the scanner  100  typically comprises an object scanning apparatus  102  configured to scan an object (e.g., human tissue). One or more images of the scanned object may be presented on a monitor  128  (that is part of a desktop or laptop computer) for human observation. In this way, targets of the object that are not visible to the naked eye (e.g., cancer cells comprised within breast tissue) may be displayed in the one or more images and, ultimately, may be detected by the human observer. 
         [0022]    The object scanning apparatus  102  is configured to scan an object under examination and transmit data related to the scan to other components of the scanner  100 . The object scanning apparatus  102  comprises an x-ray source  132  and a detector array  138 . The x-ray source  132  is configured to emit fan, cone, wedge, or other shaped x-ray configuration into an examination region  144  of the object scanning apparatus  102 . 
         [0023]    X-rays that traverse the object under examination (e.g., the object in the examination region  144 ) are detected by the detector array  138  located on a diametrically opposing side of the object from the x-ray source  132 . Targets (e.g., masses, cancer, scar tissue, etc.) within the object (e.g., a breast) may cause various amounts of x-rays to traverse the object (e.g., creating areas of high traversal and areas of low traversal within the object). For example, less radiation may traverse targets with a higher density (relative to densities of other targets in the object). It will be appreciated that the changes in traversal may be used to create x-ray images of targets within the object. For example, if breast tissue is scanned by the object scanning apparatus  102 , regions of tightly compacted cells may appear more prominently on an x-ray image than healthy breast cells (which may be virtually invisible). 
         [0024]    In one embodiment, the object scanning apparatus  102  is part of a mammography unit and the object scanning apparatus  102  further comprises a top compression paddle  134  and a bottom compression paddle  136 . A vertical support stand  142  may provide a means for suspending the compression paddles  134  and  136 , the x-ray source  132 , and the detector array  138  above the ground. For example, the vertical support may be seven feet tall so that the compression paddles  134  and  136  align with the height of breast tissue when a person is in a standing position. In one example, the compression paddles  134  and  136  are adjustable along the vertical support  142  to adjust for the varying heights of humans, and a shield  140  may protect a person&#39;s head from exposure to the x-rays. 
         [0025]    In a mammography unit, for example, the examination region  144  may be comprised between the top compression paddle  134  and the bottom compression paddle  136 . When the object (e.g., breast tissue) is inserted between the top and bottom compression paddles  134  and  136 , the object is compressed (to even out the tissue and hold the tissue still). While the object is under compression, x-rays may be emitted from the x-ray source  132 . To mitigate discomfort caused by the compression, the tissue may be compressed for a short period of time (e.g., approximately 10 seconds). X-rays that traverse the breast while it is compressed are detected by the detector array  138  that is located within and/or below the bottom compression paddle  136 . 
         [0026]    The object scanning apparatus  102  may also comprise an ultrasound component  146 . The ultrasound component  146  may be configured to emit a plurality of sound waves, electromagnetic waves, light waves, or other image producing transmission into the examination region  144 , and/or detect emitted sound waves, for example, that have interacted with the object, in such a manner that the detected sounds waves can be used to generate an ultrasound image of object that depicts a plane of the object substantially parallel to a plane depicted in an x-ray image of the object. For example, in mammography, a horizontal slice of breast tissue is depicted in an x-ray image, and the ultrasound component  146  may be configured to emit and/or detect sound waves in such a manner that it ultimately causes the resulting ultrasound image(s) to also depict a horizontal slice of breast tissue in a plane substantially parallel to the plane of the x-ray image. In one example, the ultrasound component  146  emits sound waves in a direction substantially perpendicular to a trajectory of a center x-ray beam associated with the x-ray source  132  and/or perpendicular to a detector plane formed by the detector array  138 . It will be understood to those skilled in the art that the terms “center x-ray beam” as used herein refers to an x-ray beam that impacts the detector array at a ninety degree angle (e.g., the center beam of a fan, cone, wedge, or other shaped x-ray configuration). 
         [0027]    It will be appreciated that the ultrasound component  146  may be configured to detect transmission waves and/or reflection waves depending upon its configuration. In one example, a single transducer  148  of the ultrasound component  146  both emits sound waves and detects those sound waves that have reflected off targets in the object. In another example, one transducer  148  emits sound waves and another transducer, positioned on a diametrically opposing side of the object, detects sound waves that have traversed the object under examination. 
         [0028]    It will also be appreciated that the ultrasound component  146  and/or components of the ultrasound component  146  (e.g., one or more transducers  148  comprised within the ultrasound component  146 ) may be configured to adjust (e.g., vertically) relative to the object to acquire data that may used to create a plurality of images, respective images depicting various parallel planes of the object. In this way, a plurality of ultrasound images may be formed, each ultrasound image of the plurality depicting a scanning of the object that is both substantially parallel to the planes depicted in the other ultrasound images of the plurality of images and substantially parallel to the plane depicted in the x-ray image. In one example, a doctor may take a series of ultrasound images, each depicting a unique slice of the object, for example, and compare it to an x-ray image (e.g., depicting the entire object collapsed or flattened in one plane) to determine what is below, above, and/or to the side of a mass depicted in the x-ray image. 
         [0029]    In the example scanner  100 , an x-ray data acquisition component  104  is operably coupled to the object scanning apparatus  102  and is configured to collect information and data related to x-rays that were detected by the detector array  138 . The x-ray data acquisition component  104  may also be used to compile the collected data (e.g., from multiple perspectives of the object) into one or more x-ray projections  106  of the object. 
         [0030]    The illustrated example scanner  100  also comprises an x-ray reconstructor  108  that is operably coupled to the x-ray data acquisition component  104 , and is configured to receive the x-ray projections  106  from the x-ray data acquisition component  104  and generate 2-D x-ray image(s)  110  indicative of the scanned object using a suitable analytical, iterative, and/or other reconstruction technique (e.g., backprojection from projection data space to image data). The x-ray image(s)  110  illustrate the latitudinal dimension (e.g., orthogonal to a center x-ray beam and parallel to the detector array) of the object. That is, the images may not depict the vertical height, for example, of a target inside an object when x-rays are emitted from above the object under examination. 
         [0031]    The example scanner  100  also comprises an ultrasound acquisition component  116  that is operably coupled to the object scanning apparatus  102  and is configured to collect information and data related to sounds waves that are detected by the ultrasound component  146 . The ultrasound acquisition component  116  may also be configured to compile the collected data into projection space data  118 . As an example, data from a plurality of transducers positioned about the object may be compiled into projection space data  118 . 
         [0032]    In the example scanner  100 , an ultrasound image apparatus  120  is operably coupled to the ultrasound acquisition component  116 , and is configured to receive the projection space data  118  from the ultrasound acquisition component  116  and generate ultrasound image(s)  122 . That is, ultrasound image apparatus is configured to convert sound waves into one or more images  122  using techniques known to those skilled in the art (e.g., beam forming techniques). It will be understood to those skilled in the art that the one or more 2-D x-ray images  110  and the one or more ultrasound images  122  depict substantially parallel planes of the object under examination. 
         [0033]    In another embodiment, the x-ray source  132  and/or the detector array  138  may be configured to vary their relative position to one another. For example, the x-ray source  132  may be configured to rotate about a portion of the object under examination (e.g.,  20  degrees left and right of center). In this way, data from a variety of perspectives (e.g., angles) of the object can be collected from a single scan of the object. The data from the variety of perspectives (e.g., which may be volumetric data representative of the volumetric space of the object since it is acquired from a plurality of perspectives) may be combined or synthesized by the x-ray reconstructor  108  using known digital averaging and/or filtering techniques (e.g., tomosynthesis). Each image  110 , for example, may be focused on a scanning plane (e.g., a horizontal slice) of the object, which is parallel to the detector plane, and depicts targets within a particular longitudinal range. In this way, a substantially three-dimensional image of the object under examination may be formed by stacking the two-dimensional images  110 . 
         [0034]    In another embodiment, the ultrasound component  146  is configured to acquire data from a plurality of angles along a similar scanning plane of the object. In this way, a computed tomography ultrasound (e.g., similar to a computed tomography scan using x-rays) of the object may be acquired, for example. Ultrasound data may be acquired from a plurality of angles by a rotatable ultrasound component and/or an ultrasound component that comprises a plurality of transducers situated about the object (e.g., forming an arc about the object), for example. 
         [0035]    It will be appreciated that where the ultrasound component  146  acquires data from a plurality of angles, the ultrasound image apparatus  120  may use more a suitable analytical, iterative, and/or other reconstruction technique (e.g., similar to the techniques used to generate computed tomography images from x-ray data). In one example, the ultrasound image apparatus  120  may also place emphasis on particular types of data generated based upon the detected sound waves (e.g., elastography, reflection, transmission, etc.). 
         [0036]    In some instances, the x-ray images  110  and the ultrasound images  122  may be spatially coincident to one another. That is, the plane of the object depicted in at least one x-ray image may correspond to a plane of the object depicted in at least one ultrasound image, in such a way that the ultrasound image may be overlaid onto the x-ray image or vice-versa. For example, if the x-ray images  110  depict five different planes of object (e.g., each plain representing a horizontal slice ⅕ the width of the total object), the ultrasound component and/or components of the ultrasound component may be configured to adjust so as to cause five ultrasound images  122  to be produced. Each of the five ultrasound images  122  produced may have spatial coincidence with one of the x-ray images  110 , for example. 
         [0037]    The illustrated example scanner  100  further comprises a spatial registration component  124 . The spatial registration component  124  is in operable communication with the ultrasound image apparatus  120  and the x-ray reconstructor component  108 . The spatial registration component  124  is configured to combine the one or more x-ray images  110  with one or more ultrasound images  122  to form one or more combined images  126  (through the process of fusion) when the x-ray image(s) and the ultrasound image(s) are spatially coincident (e.g., by identifying corresponding portions of the x-ray image and the ultrasound image, or more generally, by identifying corresponding portions of the x-ray data and the ultrasound data). That is, the spatial registration component  124  is configured to combine complementary information from two modalities (e.g., an x-ray image  110  and an ultrasound image  122 ) through suitable analytical techniques (e.g., retrospective registration algorithms, algorithms based on entropy, etc.). 
         [0038]    It will be understood to those skilled in the art that other configures and components for a scanner are also contemplated. In one example, a single x-ray image  110  (e.g., depicting a collapsed or flattened representation of the object) and a single ultrasound image  122  (e.g., depicting an un-flattened slice of the object parallel to the flattened x-ray image) is produced from data acquired from the object scanning apparatus  102  and the two images are visually compared (e.g., the x-ray image  110  and the ultrasound image  122  are not combined by the spatial registration component  124 ). Therefore, the scanner may not comprise a spatial registration component  124 , for example. 
         [0039]      FIG. 2  illustrates example scanning planes  200  (e.g., horizontal slices) of an object  210  that may be depicted in x-ray images  202  and/or ultrasound images  204 . When x-ray data (e.g., which may be volumetric data representative of a volumetric space of the object) is acquired at a variety of perspectives as discussed above (e.g., an x-ray source is varied with respect to an x-ray detector array) and combined and/or filtered (e.g., using tomosynthesis techniques) x-ray images depicting the illustrated example scanning planes  200  may be produced. It will be appreciated that the x-ray images  202  generally depict the various scanning planes  200  in a flattened latitudinal dimension (e.g., x, y), such that targets in a scanning plane are depicted in the image generally having no discernable z coordinate. 
         [0040]    Ultrasound images  204  depicting similar scanning planes  200  (e.g., three-dimensional slices) to those depicted in the x-ray images may also be produced. The ultrasound images  204  may depict the scanning planes  200  in a flattened latitudinal dimension or in an unflattened latitudinal dimension (e.g., depicting x, y, and z dimensions). The example ultrasound images  204  depict the scanning planes in an unflattened latitudinal dimension. That is, they are depicted as having x, y and z dimensions. Unflattened ultrasound images may be useful to more easily determine the z coordinate of a target in the object (e.g., relative to comparing a plurality of flattened x-ray and/or flattened ultrasound images depicting various scanning planes), for example. 
         [0041]    Once x-ray images  202  and ultrasound images  204  are acquired, x-ray and ultrasound image that are spatially coincident may be combined (e.g., by a spatial registration component similar to  124  in  FIG. 1 ) to form a combined image. That is, an x-ray image depicting a particular plane may be combined with an ultrasound image depicting a similar plane to form a combined image. It will be appreciated that while the images may be combined to form combined images, the ultrasound images  204  and the x-ray images  202  may also remain separated and viewed independently (e.g., manually by a physician), for example. It will also be appreciated that the ultrasound images  204  and the x-ray images may not be spatially coincident (e.g., because they depict different planes of the object  210 ). Nevertheless, they may provide helpful (diagnosis) information, such as the location of a mass/tumor in the x, y and z direction, for example. 
         [0042]      FIG. 3  is a cross sectional area (e.g., taken along line  3 - 3  in  FIG. 1 ) of an example object scanning apparatus  300  (e.g.,  102  in  FIG. 1 ). The object scanning apparatus  300  comprises an x-ray source  302  (e.g.,  132  in  FIG. 1 ), a detector array  304  (e.g.,  138  in  FIG. 1 ), and an ultrasound component  306  (e.g.,  146  in  FIG. 1 ). In the illustrated example, the x-ray source  302  is affixed to a guide mechanism  308  that is configured to rotate the x-ray source  302  about a portion of an object  310  under examination (e.g.,  20  degrees left and/or right of center). The guide mechanism  308  may be suspended from a vertical support stand  312  (e.g.,  142  in  FIG. 1 ). It will be understood to those skilled in the art that the guide mechanism  308  may be unnecessary in certain applications, such as those in which data is not collected from a variety of perspectives, the x-ray source  302  is stationary while the detector array rotates  304 , etc. 
         [0043]    X-rays  314  are emitted from the x-ray source  302  and traverse the object  310  under examination. X-rays  314  that traverse the object  310  are detected by the detector array  304  positioned on a diametrically opposing side of the object  310  from the x-ray source  302 . In the illustrated example, the object  310  (e.g., tissue) is compressed between a top compression paddle  316  and a bottom compression paddle  318  (similar to those used on mammography apparatuses) to condense and/or even out the object (e.g., to promote image quality). 
         [0044]    The ultrasound component  306  is configured to send and/or receive sound waves  320  that interact with the object  310 . In the example scanning apparatus, the ultrasound component  306  is positioned between the top compression paddle  316  and the bottom compression paddle  318  (at least one of which is configured to selectively receive the ultrasound component) and is configured to contact the object  310  under examination. Using this configuration (e.g., the ultrasound component  306  perpendicular to the detector array  304  and/or parallel to a center x-ray beam  326 ), the ultrasound component  306  may acquire data relating to the sound waves while the detector array  304  is acquiring data related to the x-rays since the two modalities occupy different space (e.g., the detector array occupies space below the object  310  and the ultrasound component  306  occupies space to the side of the object  310 ). 
         [0045]    In one example, the ultrasound component  306  is attached to, and movable along, one or both of the compression paddles  316  and  318 . Stated differently, the ultrasound component is configured to be selectively coupled to at least one of the compression paddles  316  and  318 . For example, as illustrated, one or both of the compression paddles  316  and  318  comprise tracks (e.g., along their horizontal surface) and the ultrasound component  306  slides along the tracks (e.g., substantially into and out of the page at a midline of the breast as further illustrated in  FIG. 4 ) based upon the size of the object  310  under examination, for example, to come into contact with and/or move away from the object  310 . 
         [0046]    The ultrasound component  306  may comprise one or more transducers  322  (e.g.,  148  in  FIG. 1 ). In one example, the transducers  322  are single element transducers (e.g., similar to endo-transducers) that are affixed to a guide mechanism  324 . The transducers may rotate about the guide mechanism  324  and/or move vertically along it, for example. In this way, ultrasound scans may be isolated to a particular scanning plane (e.g., horizontal slice) of the object  310  under examination. For example, data that is acquired while the one or more transducers  322  are in the upper elevation of object  310  may relate to the upper vertical portion of the object  310 , and data acquired while the one or more transducers  322  are in the lower vertical portion of the object  310  may relate to the lower vertical portion of the object  310 . Data acquired from the particular portion of the object  310  that was isolated by the transducers may be reconstructed to form an image, depicting targets comprised in a particular scanning plane of the object  310  which is parallel to the detector array  304  and parallel to a plane depicted in the x-ray image. While the illustrated object scanning apparatus  300  illustrates two transducers  322  (e.g., one on each side of the object  310 ) it will be understood to those skilled in that art that a different number of transducers  322  may be used. Additionally, the sound waves may be emitted and/or detected from another type of ultrasound mechanism, such as a multi-element probe, for example. 
         [0047]    It will be understood to those skilled in the art that the data that is acquired from substantially vertical x-rays  314  may be compiled (e.g., through reconstruction techniques) to form one or more x-ray images (e.g.,  110  in  FIG. 1 ) that depict a scanning plane of the object  310 , if the position of the x-ray source is rotated relative to the x-ray detector during the scan (e.g., to acquire data from a variety of perspectives of the object). Additionally, the x-ray images may be combined (e.g., fused) with one or more corresponding ultrasound images to form a combined image (e.g.,  126  in  FIG. 1 ). In one example, the corresponding ultrasound image is representative of data acquired while the one or more transducers were located in the scanning plane corresponding to the x-ray image. 
         [0048]      FIG. 4  illustrates the cross sectional area (e.g., taken along line  4 - 4  in  FIG. 1 ) of an ultrasound component  402  comprising a plurality of transducers  404  that may be arranged about the object in a particular scanning plane (e.g., to acquire a computed tomography ultrasound image along a plane of the object). A plurality of transducers  404  may be used, for example, to mitigate false positives in ultrasound images and/or improve image quality. In one example, a first transducer  406  of the plurality of transducers  404  may emit a first set of sound waves and the plurality of transducers  406  (e.g., including the first transducer) may listen for and/or detect the first set of sound waves. A second transducer  408  may emit a second set of sound waves once the first set of sound waves is detected, for example. After a predetermined number of transducers has emitted sound waves, for example, the plurality of transducers may reposition themselves along the object  410  (e.g., into or out of the page along a guide mechanism similar to  324  in  FIG. 3 ). In this way, the transducers  404  may detect sound waves that reflect and/or traverse the object  410  under examination, whereas a single transducer may not as thoroughly detect sound waves that traverse the object  410  under examination, for example. Additionally, using a plurality of transducers  404  may minimize artifacts (e.g., white streaks) in an image caused by areas of the object  410  that sound waves did not reach and/or areas where a weak signal was detected (e.g., because the sound waves were reflected off another target within the object). 
         [0049]    Data collected from the plurality of transducers  404  while the transducers  404  were in a particular scanning plane of the object  410 , for example, may be combined by an ultrasound acquisition component (e.g.,  116  of  FIG. 1 ) and/or reconstructed by an ultrasound image apparatus (e.g.,  120  in  FIG. 1 ) to form a tomography image of targets within the scanning plane. A second computed tomography image may be acquired based upon data detected while the transducers are in a second scanning plane of the object  410 , for example. These computed tomography images may be combined with x-ray images representing similar planes of the object  410  to form one or more combined images (e.g.,  126  in  FIG. 1 ). 
         [0050]      FIG. 5  is a cross sectional area (e.g., taken along line  3 - 3  in  FIG. 1 ) of another example object scanning apparatus  500  (e.g.,  102  in  FIG. 1 ). The example scanning apparatus  500  includes an ultrasound component  506 , which may operate as set forth in U.S. Patent Application No. 20040030227, bearing Ser. No. 10/440,427 to Littrup et al., the entirety of which is hereby incorporated by reference herein. Unlike object scanning apparatus  300  in  FIG. 3 , the ultrasound component  506  (e.g.,  306  in  FIG. 3 ) may not be in contact with the object  510  (e.g.,  310  in  FIG. 3  or  410  in  FIG. 4 ) because the object  510  is submersed in a conductive fluid  512  (e.g. water) that allows the sound waves to transfer between the object  510  and the ultrasound component  506 . The fluid  512  may be stored in a compression paddle  518  (e.g.,  318  in  FIG. 3 ) that has walls configured to mitigate fluid flow outside of the compression paddle  518 , and the ultrasound component  506  may be attached to the wall of the compression paddle  518 , for example. Additionally, the ultrasound component  506  may be capable of rotating about a scanning plane of the object  510  (e.g., in a circular plane into and out of the page). In this way, a (single) rotatable ultrasound component  506  comprising a single transducer, for example, may provide benefits similar to a plurality of transducers (e.g.,  404  in  FIG. 1 ) that are in contact with the object  510 . That is, data from a variety of perspectives may be used to produce one or more computed tomography ultrasound images of the object. In some applications, a rotatable ultrasound component  506  may be better than a plurality of transducers attached to the object because less set up time may be necessary for the procedure (e.g., a breast examination) and/or less discomfort since the transducer may not be pressed against the object  510  (e.g., breast tissue) being examined, for example. It will be appreciated that the rotatable ultrasound component  506  and/or portions of the ultrasound component may also traverse various scanning planes of the object (e.g., moving up or down the page) to produce a plurality of images, each image depicting targets in a different scanning plane of the object, for example. 
         [0051]      FIG. 6  illustrates an exemplary method  600  of presenting data acquired from two scanning modalities. The method begins at  602 , and data related to an x-ray image and data related to an ultrasound image of the object under examination are acquired such that the ultrasound image depicts a plane of the object that is substantially parallel with a plane of the object depicted in the x-ray image. In one example, the ultrasound image and the x-ray image have spatial coincidence. That is, a plane of at least one x-ray image, created from data acquired by from the x-ray modality, corresponds to a plane of an ultrasound image, created from data acquired by the ultrasound modality, in such a way that the ultrasound image may be overlaid onto the x-ray image or vice-versa. 
         [0052]    It will be appreciated that such coincidence is not be attainable with disparate equipment (e.g., separate x-ray and ultrasound acquisition devices). Similarly, such coincidence would likewise not be attainable where the object under examination is repositioned in a combined x-ray and ultrasound acquisition device (e.g., a single device is used, but data acquisition occurs at different times) because the orientation of the object would be, at least, slightly different when the different data is acquired. Nevertheless, while the different modalities (e.g., x-ray and ultrasound) may acquire data concurrently as provided herein, it is not a requisite since the system may maintain the orientation of the object during the examination (e.g., the modalities may scan the object consecutively, while the orientation of the object remains substantially fixed). 
         [0053]    X-rays are emitted from an x-ray source and detected on a detector array. In one embodiment, the detector array and x-ray source are on diametrically opposing sides of the object, and the x-rays that are detected by the detector array are those that have traversed the object under examination. Since some targets within the object may be characteristically different from other targets within the object (e.g., have different densities, made of different materials, etc.), varying amounts of x-rays will traverse different portions of the object. Data related to x-rays that are detected by the detector array is reconstructed to form an x-ray image depicting a plane of the object, and targets comprised within the plane. 
         [0054]    In one example, the object is x-rayed from a plurality of angles to acquire a plurality of two-dimensional (2-D) images of the object from varying angles, and images corresponding to the respective angles are reconstructed from data related to the detected x-rays. For example, the data may undergo tomosynthesis to produce x-ray images representing various scanning planes of the object under examination. It will be understood to those skilled in the art that the number of images that may be produced may be a function of the number of angles the object is x-rayed from (e.g., two angles may allow two images to be produced). 
         [0055]    In one embodiment, ultrasound images are acquired based upon one or more transducers of the ultrasound component that are perpendicular to the detector array and emit and/or receive sound waves that have interacted with the object under examination. To acquire a plurality of slices, the transducers and/or the ultrasound component may be adjusted along a trajectory that is substantially perpendicular to the detector array. For example, the transducers may emit and/or detect sound waves in a first scanning plane of the object to acquire data related to sound waves that interact with the object in the first plane, adjust to a second scanning plane, and emit and/or detect a second set of sound waves to acquire data related to sound waves that interact with the object in the second plane. This process may be repeated for multiple scanning planes along the trajectory. Data from respective planes may be reconstructed to acquire ultrasound images representing various scanning planes of the object under examination (e.g., a first image may depict targets comprised in the first scanning plane, a second image may depict targets comprised in the second scanning plane, etc.). 
         [0056]    In one embodiment, a computed tomography ultrasound image can be created using a plurality of transducers positioned within a scanning plane of the object. A plurality of transducers may be useful if the object under examination is dense and/or compressed, for example, to improve the image quality of ultrasound images. In one example, the plurality of transducers is positioned in a predetermined scanning plane about the object, and a first set of sound waves is emitted from a first transducer. One or more of the transducers comprising the plurality may detect the first set of sound waves. Once the first set of sound waves are detected, a second transducer of the plurality may emit a second set of sound waves, and one or more of the plurality may detect the second set of sound waves. This process may be repeated until a predetermined number of transducers emit sound waves. It will be appreciated that the plurality of transducers may also traverse various scanning planes of the object to produce a plurality of computed tomography images, each image depicting a scanning plane of the object. 
         [0057]    In another embodiment, the object is submerged in a conductive fluid, and the x-ray images and ultrasound images are acquired while the object is submersed in the fluid. In this way, one or more ultrasound transducers may rotate (e.g., in a horizontal scanning plane) about the object to produce one or more computed tomography ultrasound images. Additionally, due to the presence of the conductive fluid, the transducers do not have to be in contact with the object, thereby reducing the time of the examination and/or that discomfort that may be felt when the transducer is pushed against the object. 
         [0058]    As discussed above, one or more x-ray images may be combined with one or more ultrasound images when the ultrasound and x-ray images are spatially coincident using techniques known to those skilled in the art. In this way, images from two different modalities may be combined into a single image. This may provide doctors with additional data, such as what is below and above a mass depicted in an x-ray image, for example, to assist in determining whether a mass is malignant or benign. The method ends at  606 . 
         [0059]      FIG. 7  illustrates an example method ( 700 ) of spatial registration. The method begins at  702 , and x-rays that traverse an object under examination are detected at  704 . At  706 , an x-ray image of a plane of the object is generated based upon the detected x-rays. In one example, an x-ray source rotates about a portion of the object under examination and x-ray snapshot(s) of the object are taken at predetermined angles. Data from the one or more snapshots may be combined and filtered (e.g., through tomosynthesis) to produce one or more images depicting targets comprised within respective scanning planes (e.g., each image depicts targets in one scanning plane). 
         [0060]    At  708 , waves are emitted into the object, and the waves interact with the object in a plane that is substantially parallel to the plane depicted in the x-ray image. In one example, sound waves travel through the object in a direction that is substantially perpendicular to a center x-ray beam that was emitted from the x-ray source. 
         [0061]    At  710 , waves that interact with the object in the plane that is substantially parallel to the plane depicted in the x-ray image are detected. In one example, one or more ultrasound images are produced from the detected waves and are combined with the generated x-ray image (e.g., if they are spatially coincident) using algorithm and/or analytic techniques known to those skilled in the art. The image produced by combining the x-ray image(s) and the ultrasound image(s) may assist a user in detecting of cancer, for example. The method ends at  712 . 
         [0062]    It will be understood to those skilled in the art that the techniques herein described offer numerous benefits over techniques currently used in the art. For example, since the ultrasound component and the x-ray component produce images in similar planes and both components capture the data while the object has a particular physical position and/or orientation, the information may be more easily fused through coincidence (e.g., alignment) of the planes depicted in the x-ray and ultrasound images. That is, an ultrasound image of a plane of the object can be easily fused with an x-ray image of a similar plane of the object. In some instances, such as where tissue is compressed during the examination, the ability to acquire data from two modalities at once, for example, may reduce the time the tissue is compressed, thereby lessening the duration of the discomfort caused by the compression. Additionally, in the cancer screening, for example, the additional data acquired from using two modalities may reduce the number of false positives in the initial screening and mitigate emotional distress. 
         [0063]    The application has been described with reference to various embodiments. Modifications and alterations will occur to others upon reading the application. It is intended that the invention be construed as including all such modifications and alterations, including insofar as they come within the scope of the appended claims and the equivalents thereof. For example, a, an and/or the may include one or more, but generally is not intended to be limited to one or a single item.