Patent Publication Number: US-8126226-B2

Title: System and method to generate a selected visualization of a radiological image of an imaged subject

Description:
BACKGROUND OF THE INVENTION 
     The subject matter generally relates to the field of radiology imaging and, more particularly, to a system and method to create a visualization that enables faster analysis of radiology image data. Although the subject matter is described with respect to medical imaging, and in particular mammography, the subject matter can also be applied to industrial imaging of miscellaneous subject matter (e.g., security screening, etc.). 
     Radiology imaging generally employs translation of a measured attenuation of transmitted x-rays through an imaged subject into image data of the anatomical structure of the imaged subject for illustration on a display. 
     A certain known type of radiological imaging system is employed in mammography to acquire radiological images of breast tissue. Generally, multiple different views of the breast tissue are desired in diagnostic mammography. Each of the multiple different views generally corresponds to a different position of the X-ray source and the image receiver in relation to the breast tissue. 
     Mammography is widely used today in the detection of radiological signs associated with lesions and the prevention of breast cancer. These signs may be either calcium deposits or cases of opacity. Calcium deposits are called microcalcifications and individually form small-sized elements (ranging from 100 μm to 1 mm in diameter) that are more opaque to X-rays than the surrounding tissues. Opacities are dense regions where the X-rays are absorbed more intensely than in the adjacent regions. 
     A typical mammography image generally includes projections of superimposed structures that interfere with a desired visibility of the breast tissue. These projections of the superimposed structures increase opportunities of a false positive interpretation if a structure resembles a lesion, or a false negative interpretation if the structure obscures the visibility of the lesion. 
     A typical resolution of a mammography image detector is about 100 μm. To address the limitations of projected views in mammography images, image data is acquired from several projections and at different angles of a volume of interest. This image data is then applied to a tomography reconstruction algorithm to create a digital, three-dimensional reconstruction of the volume of interest. As a result of the above, screening or interpretation of this digital, three-dimensional reconstruction of the volume of interest typically involves screening or reviewing of a large amount of image data in a sequential manner on a slice-by-slice (e.g., 50 to 80 tomography slices of image data) in the search for a small piece of information of clinical interest, such as a radiological sign of between 100 μm and 1 mm in size. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Accordingly, there is a need for an imaging system and method that enhances efficiency and reduces the time to screen through a large amount of image data of a three-dimensional, tomographic image reconstruction of a volume of interest in the search for radiological signs of clinical interest. There is also a need for a system and method reduces a probability of a false interpretation in the search for radiological signs of clinical interest. 
     The embodiments of the subject matter described herein address the needs described above. In particular, the subject matter described herein provides a system and method of imaging that improves visualization and reduces a time to screen through acquired image data in the search for radiological signs of clinical interest. 
     In accordance with one embodiment, a method to illustrate image data of an imaged subject as acquired by a radiological imaging system is provided. The method includes the steps of acquiring a plurality of two-dimensional, radiography images of an imaged subject; generating a three-dimensional reconstructed volume from the plurality of two-dimensional, radiography images; navigating through the three-dimensional reconstructed volume, the navigating step including receiving an instruction from an input device that identifies a location of a portion of clinical interest within the three-dimensional reconstructed volume; calculating and generating additional view of the volume portion of the three-dimensional reconstructed volume identified in the navigation step; and reporting the at least one additional view or at least one parameter to calculate and generate the additional view. 
     In accordance with another embodiment, a system to illustrate image data of an imaged subjected is provided. The system comprises an imaging system operable to acquire a plurality of two-dimensional, radiography images of the imaged subject, an input device, an output device, and a controller in communication with the imaging system, the input device, and the output device. The controller includes a memory with a plurality of program instructions for execution by a processor, the plurality of program instructions representative of the steps comprising generating a three-dimensional reconstructed volume from the plurality of two-dimensional, radiography images, navigating through the three-dimensional reconstructed volume, the navigating step including receiving an instruction from an input device that identifies a location of a volume portion of the three-dimensional reconstructed volume, calculating and generating an additional view of the volume portion of the three-dimensional reconstructed volume identified in the navigation step, and reporting the at least one additional view or at least one parameter to calculate and generate the additional view. 
     Embodiments of varying scope are described herein. In addition to the aspects described in this summary, further aspects will become apparent by reference to the drawings and with reference to the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an embodiment of a system operable to automatically generate a selected visualization of an anatomical region of interest of an imaged subject. 
         FIG. 2  illustrates a flow diagram of an embodiment of a method to automatically generate a selected visualization of an anatomical region of interest of an imaged subject using the system illustrated in  FIG. 1 . 
         FIG. 3  shows a schematic diagram of an embodiment of the simultaneous global display comprised of a series of tomosynthesis slice frames and a localized display of a selected slice frame along a ray path including a maximum intensity pixel (MIP). 
         FIG. 4  illustrates a schematic diagram of an embodiment of the simultaneous global display and a localized display of a three-dimensional volume of interest in spatial relation to a tracked tool. 
         FIG. 5  shows a schematic diagram of an embodiment of the simultaneous global display and an additional view of a volume of interest portion at a one-to-one scale. 
         FIG. 6  illustrates a schematic diagram of an embodiment of the simultaneous global display and a localized display of identified with a zoom tool shown in the global display. 
         FIG. 7  illustrates a schematic diagram of an embodiment of generating a display of the volume of interest. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments, which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense. 
       FIG. 1  illustrates an embodiment of a system  20  operable to generate a selected visualization of a region of interest of an imaged subject  22 . The system  20  generally includes an imaging system  25  operable to acquire multiple different views of anatomical images of the imaged subject  22 . 
     The illustrated embodiment of the imaging system  25  is configured to acquire diagnostic mammography images of a breast tissue of the imaged subject  22 . The imaging system  25  is generally operable to generate a two-dimensional, three-dimensional, or four-dimensional image data corresponding to an area of interest of the imaged subject  110 . Although the illustrated type of the imaging system  25  is mammography, the type of imaging system  25  can vary. For example, the type of imaging system  25  can include, but is not limited to, computed tomography (CT), magnetic resonance imaging (MRI), X-ray, positron emission tomography (PET), ultrasound, angiographic, fluoroscopic, and the like or combination thereof. The imaging system  25  can be of the type operable to generate static images acquired by imaging systems (e.g., CT systems, MRI systems, etc.) prior to a medical procedure, or of the type operable to acquire real-time images with real-time imaging systems (e.g., angioplastic systems, etc.) during the medical procedure. Thus, the types of images generated by the imaging system  25  can be diagnostic or interventional. 
     The illustrated embodiment of the imaging system  25  generally includes an energy source  35  (e.g., x-ray emitting tube) in communication with an image receptor  40  in a known manner so as to generate radiological images of the imaged subject  22  located therebetween. A focus  45  is operable to emit an energy beam  48  (e.g., x-ray beam) generated by the energy source  35 . Examples of the image receptor  40  include x-ray image intensifier tube, solid state detector, gaseous detector, or any type of detector which transforms incident x-ray photons either into a digital image or into another form which can be made into a digital image by further transformations. Embodiments of the image receptor  40  can be flat or curved-shaped. 
     The illustrated embodiment of the imaging system  25  further includes a gantry  50  constructed in mobile support of the energy source  35  and image receptor  40  in relation to the imaged subject  30 . The illustrated gantry  50  includes a vertical column  65  coupled to a mobile arm  70 . The mobile arm  70  can be generally C-shaped or U-shaped or other shape (e.g., L-shaped, circular, etc.). The image receptor  40  is coupled to the mobile arm  70  and positioned opposite the energy source  35  in the direction of emission so as to receive energy beam  48 . The mobile arm  70  is operable to move the energy source  35  and/or the image receptor  40  between a vertical, horizontal, or various oblique orientations. An embodiment of the mobile arm  70  is pivotally coupled to the vertical column  65  so as to shift or move the source  35 , yet leaving the receptor  45  immobile. Another embodiment of the mobile arm  70  is operable to simultaneously move the energy source  35  and the image receptor  40  in relation to the imaged subject  22 . 
     The illustrated embodiment of the mobile arm  70  is coupled to a breast-holder tray  75  configured to receive the region of interest (e.g., the breast) of the imaged subject  22 . This breast-holder tray  75  is located on top of or above the image receptor  40 . The embodiment of the imaging system  25  further includes a compression paddle  80  coupled to a hinged arm  85 . The compression paddle  80  is configured to either be manually or motor-driven (e.g., a carriage) so as to slide in a direction between the energy source  35  and the image receptor  40 , thereby compressing the breast tissue of the imaged subject  22  against the breast-holder tray  75 . The compression paddle  80  is comprised of a material (e.g., plastic, polycarbonate, etc.) so as to be generally transparent to the energy beam  48 . The compression force applied by the compression paddle  80  in relation to the breast-holder tray  75  is operable to generally immobilize the breast tissue and to enhance the image quality of the acquired images of the breast tissue by the imaging system  25 . 
     Examples of the imaging system  25  include the SENOGRAPHE® DS system as manufactured by GENERAL ELECTRIC®, the PLANMED NUANCE® system as manufactured by PLANMED, the GIOTTO IMAGE® system as manufactured by IMS®, the SELENIA® system as manufactured by HOLOGIC®, the SECTRA MICRODOSE MAMMOGRAPHY™ system as manufactured by SECTRA® and the MAMMOMAT NOVATION DR® system as manufactured by SIEMENS®. 
     In order to enable the study of each part of the breast of the imaged subject  22 , the beam  48  may be oriented in a multitude of directions about the breast tissue of the imaged subject  22 . Upon receiving the attenuated energy beam  48  having passed through the imaged subject  22 , the receptor  40  translates the detected attenuation of energy into an image of the anatomical structure of interest. 
     For mammography screening, generally a cranio-caudal and an oblique medio-lateral projection of image acquisition is typically performed on each breast. After having received the multitude of beams  48  which cross a part of the anatomical area of interest, the image receptor  40  generally emits electrical signals corresponding to the intensity of the detected attenuated energy. These electrical signals may then be translated to generate a projection image (e.g., X-ray image) corresponding to the anatomical area of interest. The imaging system  25  may also include software operable to generate a three-dimensional, reconstructed model or image of the anatomical area of interest from a series of acquired projection images generated from the multitude of directions of the energy beam through the imaged subject  22 . 
     The system  20  further includes a navigation system  100  operable to track movement and/or locate a tool  105  traveling through the imaged subject  22 . An embodiment of the tool  105  includes surgical tool, navigational tool, a guidewire, a catheter, an endoscopic tool, a laparoscopic tool, ultrasound probe, pointer, aspirator, coil, or the like employed in a medical procedure. Yet, the type of tool  105  can vary. 
     An embodiment of the navigation system  100  is generally operable to track or detect a position of the tool  105  relative to the at least one acquired projection image or three-dimensional reconstructed model generated by the imaging system  115 . An embodiment of the navigation system  100  includes an array or series of tracking elements  110  and  115  connected (e.g., via a hard-wired or wireless connection) to communicate position data (See  FIG. 1 ). Yet, it should be understood that the number of tracking elements  110  and  115  can vary. An embodiment of the tracking elements  110  and  115  comprises at least one transmitters or dynamic references in electromagnetic communication or electromagnetically coupled with one or more receivers. At least one of the tracking elements  110  transmits a field of electromagnetic energy (e.g., 10-20 kHz) operable to be detected by at least one other tracking elements  115 . In response to passing through a field of electromagnetic energy, the receiver  115  generates a signal indicative of a special relation to the transmitter  110 . Yet, it should be understood that the type of mode of coupling, link or communication (e.g., rf, infrared light, etc.) operable to measure a spatial relation or orientation can vary. 
     In accordance with one embodiment, one of the tracking elements  110  or  115  is attached at the tool  105  being tracked traveling through the imaged subject  22 . The other of the tracking elements  110  and  115  is attached at a reference (e.g., the imaged subject  22 , the gantry  50 , etc.). The navigation system  125  is operable to track movement of the object  105  in accordance to known mathematical algorithms programmed as program instructions of a software. Examples of known navigation software to track movement include INSTATRAK® as manufactured by the GENERAL ELECTRIC® Corporation, the STEALTHSTATION® as manufactured by MEDTRONIC® Corporation, and KOLIBRI® as manufactured by BRAINLAB® Corporation. The exemplary software is also operable to use two- or three-dimensional MRI, CT and/or X-ray acquired image data generated by the imaging system  25  to build a digitized three-, or four-dimensional anatomical roadmap or model of a patient&#39;s anatomy, and electromagnetic (EM) tracking technology that operates as a type of global-type positioning system to show a real-time spatial relation or location of the tool  105 , as illustrated with a representation  120  (a cursor, triangle, square, cross-hairs, etc.), relative to the anatomical roadmap. 
     The system  20  also includes a controller  130  connected in communication with the imaging system  25  and the navigation system  100 . The controller  130  generally includes a processor  135  in communication in a conventional manner with a memory  140 . The memory  140  generally includes a data memory and a program memory  140  configured to store computer readable program instructions to be executed by the processor  135 . 
     The controller  130  is also connected in communication with an input device  145  and an output device  150 . Examples of the input device  145  include a keyboard, a touch-screen, mouse device, toggle switches, joystick, etc. or combination thereof. Examples of the output device  150  include a monitor, an audible speaker, light-emitting diodes (LEDs), etc. or combination thereof. An embodiment of the output device  150  includes a screen or monitor (e.g., liquid crystal monitor) operable to display multiple viewports or panes or windows (e.g. as generated using MICROSOFT Windows®)  160  and  165 . Of course, the output device  150  can include additional monitors or screens and is not limiting on the subject matter described herein. 
     Having described a general construction of one embodiment of the system  20 ,  FIG. 2  illustrates a general description of an embodiment of a method  200  of operating the system  20  to generate a selected visualization of a region of interest of an imaged subject  22 , making it possible to dynamically reveal an image element (e.g., pixels, voxels) that includes data indicative of a radiology sign of a suspected lesion. It should also be understood that the sequence of the acts or steps of the method  200  as discussed in the foregoing description can vary. Also, it should be understood that the method  200  may not require each act or step in the foregoing description, or may include additional acts or steps not disclosed herein. An embodiment of the acts or steps of the method  200  can be in the form of a computer-readable program instruction for storage in the memory  140  and execution by the processor  135  or a computer in general. 
     Step  205  includes acquiring a plurality of projected images (P 1  through Pn) at a plurality of directions or angles (D 1  through Dn) of the anatomical area of interest (e.g., the breast tissue) of the imaged subject  22 . 
     Step  210  includes generating a digital, three-dimensional, reconstructed model or volume  212  of the imaged anatomy. An embodiment of the three-dimensional, reconstructed volume  212  is created by applying a back-projection reconstruction algorithm to the acquired image data or any other 3D reconstruction algorithm, generating a series of slice planes  214 ,  216 ,  218  of image data in succession relative to one another. A term used to refer herein to this technique is tomosynthesis. All or a portion of the acquired image data or frames (e.g., two-dimensional radiological image frames) can be used during this tomosynthesis reconstruction to generate the digital, three-dimensional reconstructed volume  212  of the imaged anatomy (e.g., breast tissue). 
     Step  220  includes detecting or identifying one or more radiological signs or voxels of an opacity to be suspect or candidates of a lesion in the imaged anatomy. An embodiment of step  220  includes applying an opacity or radiology sign detection algorithm to calculate the particular elements (e.g., pixels, voxels, etc.) of the three-dimensional, reconstructed volume likely to include image data of an opacity or radiology sign correlated to a candidate lesion. According to one embodiment, the radiological sign detection algorithm is applied to the pixels that constitute the two-dimensional image frames acquired by the imaging system  25 . According to another embodiment, the opacity detection algorithm is applied to the voxels that constitute the slice planes  214 ,  216 ,  218  of the digital, three-dimensional reconstructed volume  212  generated by the imaging system  25 . 
     For example, an embodiment of step  220  includes calculating an intensity level (e.g., contrast, grayscale, etc.) of each image element (e.g., pixel or voxel) of each slice  214 ,  216 ,  218  of the generated three-dimensional volume  212 . The terms of “contrast” or “grey” or “grayscale” levels of the opacity or radiological sign of a suspect lesion refer to a parameter value of the image elements corresponding to more strongly absorbed or greater attenuation of energy (e.g., radiation) relative to image elements of other imaged anatomical structures. Step  220  further includes comparing the calculated values of the intensity of each image element relative to predetermined conditions or threshold values indicative of opacities or radiological signs of the suspect lesion. For those image elements (e.g., pixels, voxels, etc.) within the predetermined threshold or range of the opacity or radiological sign (e.g., microcalcification), step  220  includes assigning those image elements with a designation and graphical representation indicative of candidacy to be the suspect lesion that is viewable at the output device  150  to the user. 
     Step  225  includes calculating a bounding surface or marker  226  to delineate and highlight the one or more elements of radiology sign or opacity to be the suspect lesion, as described in step  220 . This embodiment of the bounding surface  226  can generally demarcate a maximum spatial extent, herein referred to as a volume of interest (VOI)  228 , of the image elements (e.g., pixels, voxels) identified to include radiological sign or opacities of the suspect lesion in the three-dimensional, reconstructed volume  212 . 
     One embodiment of step  225  includes calculating the bounding surface  226  of the VOI  228  to be located at the extreme positions of the elements (e.g., pixels, voxels, etc.) of radiological sign or opacity of a suspect lesion. Accordingly, for each image element of the radiology sign of the suspect lesion, this embodiment of step  225  includes calculating a position of each of each of the image elements (e.g., pixels or voxels) along the axes X, Y and Z that defines the spatial relation and orientation of the VOI  228  or three-dimensional, reconstructed volume  212 . For each axis X, Y or Z, this embodiment of step  225  includes calculating those image elements having a minimum position and a maximum position (e.g., Xmin, Xmax, Ymin, Ymax and Zmin, Zmax) relative to the axes X, Y and Z. The locations of those elements are identified to demarcate an extent of the bounding surface  226  of VOI  228  of the three-dimensional, reconstructed volume  212  identified to include the suspect lesion. 
     A second embodiment of step  225  includes calculating or generating a mathematical model that defines a shape (e.g., ellipsoid, cylinder, sphere, etc. or combination thereof) of the bounding surface  226  that defines the VOI  228  identified in the three-dimensional, reconstructed volume  212  identified to include the suspect lesion. This embodiment of step  225  includes applying an algorithm to calculate a distribution of the image elements (e.g., pixels, voxels) identified to include a radiology sign or opacity of the suspect lesion, and then correlating the distribution of the image elements to a parametric shape and size as defined by the mathematical model to be the bounding surface  226  of the VOI  228  that at least envelopes the suspect lesion. The shape and size of the bounding surface  226  defined by the mathematical model can vary. 
     An embodiment of step  225  further includes comparing the bounding surface  226  to predefined constraint parameters (e.g., shape and size) of the suspect lesion, and changing the shape or size of the bounding surface  226  accordingly to satisfy the predefined constraint parameters. 
     An embodiment of step  225  further includes identifying or calculating the succession of slices  214 ,  216 ,  218  that constitute the three-dimensional, reconstructed volume  212  as having a non-null intersection with the bounding surface  226 , and re-calculating the bounding surface  226  to define or identify this non-null intersection. An embodiment of the two-dimensional bounding surface is of a geometrical shape calculated to be a best correlation or fit to the VOI  228 . 
     The bounding surface or markers  226  are generally configured to reveal, define or demarcate the positions image elements of the VOI  228  or of the digital, three-dimensional reconstructed volume  212  that includes or envelopes the radiological sign of the suspect lesion for illustration to the user. An embodiment of the boundary surface or markers  226  may be three-dimensional, two-dimensional or one-dimensional. For each-dimensional type of boundary surface  226 , a three-dimensional viewing algorithm is applied. Should the boundary surface  226  be two-dimensional or one-dimensional, the viewing of the volume  212  or the VOI  228  is implemented in continuously displaying the slices  214 ,  216 ,  218  of the digital volume  212  or the VOI  228  on the screen  160  or  165 , giving the illusion of motion. Should the markers  226  be three-dimensional, the viewing of the reconstructed volume  212  or the VOI  228  is implemented by a three-dimensional viewing algorithm firstly enabling the display of the reconstructed volume  212  or the VOI  228  on the screen  160 , as well as enabling the practitioner to view the volume  212  or the VOI  228  at different viewing angles. The use of the volumetric viewing algorithm draws the practitioner&#39;s attention to the VOI  228 . 
     Another embodiment of step  225  includes communicating the acquired image data to a computer-aided detection system  230  of the controller  130 , herein referred to as a CAD system  230 . The CAD system  230  can be integrated with the controller  130  or be stand-alone and coupled in communication therewith. The CAD system  230  is operable to process the acquired medical image data that constitutes the series of acquired images or the generated digital, three-dimensional reconstructed volume  212 , so as to calculate quantitative data (e.g., greyscale level, contrast, intensity, etc.) indicative of zones of radiological signs reflecting a presence of a suspect lesion. 
     The CAD system  230  can also generate the boundary surface or markers or graphical representations  226  to demarcate or define the zones or series of image elements that identify or envelope the suspect lesion. An embodiment of the CAD system  230  locates the markers  226  at the x and y coordinates of a location of the general center of the VOI  228 . It can be represented for example by any graphic annotation defined beforehand or by a blinking feature or by color. 
     Referring to  FIGS. 2 and 7 , step  280  includes generating and illustrating a global overview image  285  of the digital, three-dimensional reconstructed volume  212  or a set of overview slabs. The global overview image  285  can be displayed in combination with the bounding surfaces  226  that define or identify the VOI  228  for illustration at the output device  150 . The bounding surfaces  226  can be illustrated at the first viewport  160  with a constraint of transparency that prevents the bounding surfaces  226  from masking image data pertaining to radiology signs in the digital, three-dimensional reconstructed volume  212 . 
     An embodiment of the global overview image  285  is one of the group including a projection image (P 1  to Pn) as generated at the acquiring step  205 , a set a overview slabs, a reprojection image  292  or a three-dimensional display of the three-dimensional, reconstructed volume  212  correlated to a selective virtual viewpoint per an instruction that includes a location received via the input device  145 . The step  280  generally aids the user in more rapidly analyzing or filtering through the image data constituting the three-dimensional, reconstructed volume  212  and for the reprojection in comparing the volume  212  to prior 2D standard acquisitions. 
     If the overview image  285  includes the reprojection image  292  or a three-dimensional display, step  280  can also include calculating the user&#39;s selected viewpoint of the digital, three-dimensional reconstructed volume  212  or the VOI  228 . For sake of example, assume the selected viewpoint can be represented as a camera view of digital, three-dimensional reconstructed volume  212  defined by a virtual source or viewpoint  295  relative to a virtual detector  296  (See  FIG. 3 ). The viewing algorithm is operable to calculate the two-dimensional rendering of the digital, three-dimensional reconstructed volume  212  from the viewpoint as input by the user via the input device  145  (e.g., movement or clicking of the mouse device  145  in spatial relation to the digital, three-dimensional reconstructed volume  212 ). Via the viewing algorithm, the system  20  is operable to generate the overview image  285  of the digital, three-dimensional reconstructed volume  212  from a virtual viewpoint at different angles and from different positions around the digital, three-dimensional reconstructed volume  212 . 
     Alternatively to using the global overview image  285 , the user can use a set of overview slabs that are obtained in combining elements of volume portions; wherein optionally the set of volume portions is sub-sampled with an overlap between two consecutive portions. 
     An embodiment of step  280  includes calculating the global overview image  285  or a set a overview slabs in considering an image element (e.g., pixel, voxel) with a maximum intensity pixel (MIP) value or minimum intensity pixel (MinIP) value that lies along a ray path (illustrated by arrow and reference  297  in  FIG. 3  defined by the direction of the source  35  to the detector  40 , or by the user-defined virtual source or viewpoint  295  and the virtual detector  296 ) directed from the virtual viewpoint or source  295  to each element of the virtual detector  296 . MIP or MinIP can be replaced by any transformation that gives rise to a value from the voxel values along the considered ray paths. When using MIP (with respect to MinIP) rendering, a depth map can be created storing for each pixel of the overview image an information allowing to retrieve the slice containing the maximum (resp. minimum) grey intensity level along the ray path going from the virtual source to the pixel. In a particular embodiment, an automatic detection of radiological signs can be applied and the contrast of the detected signs can be enhanced in the reconstructed volume  212  to increase the probability of being visible in the global overview image or overview slabs. 
     Step  300  generally includes receiving instructions of navigation for navigating through the image elements that constitute the overview image  285  of the three-dimensional volume  212  and identifying a location of a portion of the volume  212 . An embodiment of step  300  includes creating a slice-by-slice paging or cine-looped display mode of the succession of slices  214 ,  216 ,  218  of the three-dimensional reconstructed volume  212  and stop on a particular slice of interest constituting the portion itself or the central slice of the volume portion. 
     Another embodiment of step  300  includes creating a slab per slab paging or cine-looped display mode of the succession of overview slabs and stop on a particular slab of interest constituting the volume portion itself. 
     An embodiment of step  300  includes receiving instructions via the input device  145  in navigating through the image data of the overview image  285  of volume  212 . The input device  145  can be employed to create an instruction that identifies or selects (e.g., via a mouse click) one or more pixels in the two-dimensional rendering of the above-described global overview image  285  (e.g., the reprojection  292  or the three dimensional display of the volume  212 ) or in one of the overview slabs. For example, the user can select the voxel that includes a contrast or grayscale level value that is of an increased likelihood to be the suspect lesion. 
     Having computed a location of at least one image element of the overview image  285  or of one overview slab having a parameter value (e.g., MIP) within a predetermined threshold of a radiological sign of a suspect lesion in the imaged subject  22 , or having computed at least one bounding surface  226  having coordinates that defines the location of the outermost boundary of the at least one image element that constitutes the radiological sign of the suspect lesion, an embodiment of step  300  includes detecting or receiving an instruction that includes a selected location via input device  145  of at one of the image element that constitutes the volume  212  or the overview image  285 , and in response displaying a volume portion. 
     For example, step  300  can include receiving an instruction indicative or identifying the bounding surface or marker  226  at the volume  212  or the overview image  285  to be enlarged and illustrated in the second display window  165 . This embodiment of step  300  includes receiving an instruction (e.g., click of a mouse device) so as to identify the marker or boundary surface  226  of the VOI  228  to be enlarged and simultaneously illustrated in the second viewport  165  along with the digital, three-dimensional reconstructed volume  212  illustrated in the first viewport  160 . Similar to the first embodiment, the contrast or intensity level of the illustration marker or bounding surface  226  can be set to a maximum level so as to further highlight or delineate relative to the image elements that constitute the volume  212  or the overview image  285 . 
     According to another embodiment, step  300  includes receiving an instruction (e.g., click of a mouse device  145  at the bounding surface or marker  226 ) that identifies the VOI  228  and in response calculating and communicating one of a slice  214 ,  216  or  218  from the sequential succession of slices  214 ,  216 ,  218  most centrally located in spatial relation to the VOI  228  constituting thereof, or a subset of the succession of slices  214 ,  216 ,  218  that are located between an identified minimum and maximum coordinate value of the VOI  228 , a slab representative of an average of the successive series of slices  214 ,  216 ,  218 , a three dimensional display of the VOI  228 . 
     Alternatively, step  300  can include receiving instructions via the input device  145  to switch or alternate from amongst a series of partial views or slices or set of slabs of interest that constitute the volume  212  or VOI  228 . 
     Step  320  includes calculating and generating a partial view, two-dimensional display  322  of a volume portion  323  of clinical interest of the three-dimensional, reconstructed volume  212  correlated to the location of the at least one image element identified per the instruction received from the input device  145  in the navigating step  300 . The volume portion  323  of clinical interest can be considered to comprise a fragment or component of interest that makes up the reconstructed volume  212 , for example voxels illustrative of the candidate lesion. An embodiment of step  320  includes illustrating the two-dimensional display  322  in the second viewport or pane or window  165  in simultaneous illustration with one of the volume  212  or the VOI  228  or the overview image  285  as described above and shown in the first viewport  160 , the first viewport  160  independent of the second viewport  165 . An embodiment of the two-dimensional display  322  as illustrated in the second viewport  165  is at a scale (e.g., one to one) that is greater relative to the scale of the illustration of the volume  212  or the VOI  228  or the overview image  285  in the first viewport  160 . The second viewport  165  may also be located (e.g., centrally located) at the selected image element of the volume  212  or the VOI  228  or the overview image  285  in the first viewport  160 . Examples of the volume portion  323  include at least one slice of image data of interest  324  (e.g., a central slice), at least one or successive set of slabs  326  (using conic or parallel ray paths) representative of a combination of volume elements, or a three-dimensional image or model  328  of the volume portion  323 . 
     For example, in response to receiving the instruction from the input device  145 , step  320  can include automatically calculating or selecting the slice  218  from the succession of slices  214 ,  216 ,  218  along the ray path  292  of the selected image element (e.g., voxel, pixel, etc.) identified per an instruction (e.g., click of a mouse device) generated via the input device  145 . For example, assume having computed the image element constituting the overview image  285  that includes the MIP in the direction of radiation or ray path  297  through the imaged subject  22  toward the detector  40 , and for each pixel of the overview image, generating a depth map that includes the image element having the MIP and storing in the memory  140  of the controller  130 . Upon receiving or detecting an instruction correlated to a click of the input device  145  over an image element of the overview image  285  per step  300 , step  320  can include automatically illustrating the slice which index is stored in the depth map at the location of the image element of interest per the instruction communicated by the input device  145 . 
     In yet another example, having detected or identified a location of the suspect lesion in the three-dimensional, reconstructed volume  212  or the overview image  285  as located with the CAD marker  226  such that upon receiving an instruction that includes the location of the marker  226  via the input device  145 , step  320  includes creating the two-dimensional display  322  of the portion of interest of the three-dimensional, reconstructed volume  212  for illustration in the second viewport  165  simultaneously with the illustration of the three-dimensional, reconstructed volume  212  or the overview image  285  in the first viewport  160 . The two-dimensional display  322  of the portion of interest can include one of a slice of image data, a slab generally representing a combination of successive series of slices, and a reprojection image  292  dependent on or correlated to a selective virtual viewpoint or ray path  297  per the instruction received via the input device  145  or a three dimensional display. 
     According to yet another example, having detected or tracked a location of the tool  105  through the imaged subject  22  via the tracking system  100 , and registering the location of the tool  105  relative to the spatial relation of the three-dimensional, reconstructed volume  212  or the VOI  228  or the overview image  285  such that the controller  130  is operable to calculate the location of the one or more image elements that constitute the three-dimensional, reconstructed volume  212  or the VOI  228  or the overview image  285  correlating to the location of the tool  105 , step  320  includes calculating and generating the two-dimensional display  322  of the portion of interest of the three-dimensional, reconstructed volume  212  or the VOI  228  or the overview image  285  that is correlated or dependent or centered at the location of the tool  105 . An embodiment of the two-dimensional display  322  can be continuously or periodically updated with movement of the tool  105  relative to the imaged subject  22 . 
     Step  340  includes generating a report  342  generating or creating additional views or information that represent the region of clinical interest within the three-dimensional dataset. This new information can be intended for instance to be viewed by a referring physician and may be part of the exam report. For some medical applications such as mammography, it can be critical to print or display the two-dimensional display  322  automatically at a one-to-one scale. One-to-one scale is of particular interest when comparing current image data with prior acquired image data, such as performed with high resolution imaging such as mammography or to assess the true size of a lesion. Embodiments of step  340  include creating a storing the two-dimensional display  322  of a portion of the three-dimensional, reconstructed volume  212  or the VOI  228  or the overview image  285  as a new DICOM image in the study stored in the memory  140 . Another embodiment of step  340  includes generating a bookmark  346  that stores information to calculate or generate the volume portion. For example, the bookmark  346  may be represented by any graphical representation (e.g., coupled flag, color, etc.) that delineates the identified slice  218  from the remainder in the succession of slices  214 ,  216 ,  218  constituting the three-dimensional, reconstructed volume  212 . Another embodiment of the step  340  includes generating and key image note  348  to the identified slice  218 . An example of the key image note  348  is a DICOM normalized object represented as a graphic annotation or alphanumeric text (e.g., different thickness of border, a color, etc.) that highlights the partial view two-dimensional display  322  relative to the remainder of image data constituting the three-dimensional, reconstructed volume  212  or the VOI  228  or the overview image  285 . Yet another embodiment of step  340  includes saving the partial view two-dimensional display  322  illustrated in the second window frame  165  in an exportable save state  350 , as a graphic file  352  (e.g., as a pdf or html file format) for storage to the memory  140 , or save to a known storage medium  354  (e.g., burn to a DVD, hard drive of a computer, etc.). 
     Yet another embodiment of step  340  includes automatically generating and printing the partial view, two-dimensional display  322  illustrated in the second viewport  165  as a printout  356  at a one-to-one scale relative to the imaged anatomical structure, where the output device  150  includes a printer (e.g., laser printer, ink-jet, etc.). 
     This written description uses examples to disclose the subject matter described herein, including the best mode, and also to enable any person skilled in the art to make and use the subject matter. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.