Patent Description:
In security applications, the three-dimensional volumetric or two-dimensional projection images can be used to detect suspicious or dangerous objects hidden in baggage or cargo, for example, contraband. In medical applications, the three-dimensional volumetric or two-dimensional projection images can be used to detect organic or inorganic structures related to disease or injury within a biological organism.

<CIT> discloses a method and system to analyze the content of a packed bag utilizing a scanner. The bag is scanned for a scannable characteristic to acquire scan data representative of a content of the piece of baggage. A volumetric data set is generated from the scan data, wherein the volumetric data set includes voxel values of the scannable characteristic throughout a volume of interest in the baggage. A rendered view is produced of the content of the piece of baggage based on the voxel values within a selected range from the volumetric data set. The method and system also provide identifying a threat by analyzing Hounsfield Units of the material of interest.

<CIT> describes graphical user interfaces and methods for displaying ECG, slice images and a reconstruction projection image of the slices. In exemplary embodiments, the graphical user interfaces and methods facilitate the selection of slice images that are taken during a quiet part of the patient's heart cycle in which the heart is relatively motionless so as to reduce blurring and the introduction of artifacts into the resultant reconstructed projection image of the heart. In exemplary embodiments, the resultant projection image can be used for coronary calcium detection and scoring or <NUM>-D rendering.

<CIT> discloses systems and methods for computer tomography (CT) imaging. An attenuation transform component configured to map voxels in a received set of cross-sectional CT images to associated brightness values according to a piecewise transform function to produce a set of transformed images. A user interface is configured to provide the set of transformed images to a user at an associated display.

<CIT> describes methods, and associated systems comprising processors, input devices and output devices, of detecting regions of interest in a tomographic breast image. The methods may comprise: acquiring tomographic breast image data; deriving a plurality of synthetic sub-volumes from the tomographic breast image data; wherein each subvolume is defined by parallel planar top and bottom surfaces; wherein planar top and bottom surfaces of successive subvolumes are parallel to each other; and wherein a top planar surface of a sub-volume is offset from a top planar surface of a prior sub-volume, such that successive sub-volumes overlap; for each sub-volume, deriving a two-dimensional image; for each two-dimensional image, identifying regions of interest therein; deriving at least one region of interest of potential clinical interest from a plurality of identified regions of interest; and outputting information associated with at least one derived region of interest of potential clinical interest.

According to a first aspect of the present invention, there is provided a method according to claim <NUM>. Optional features of the method are outlined in claims <NUM> to <NUM>.

According to a second aspect of the present invention, there is provided an imaging system according to claim <NUM>.

Taught herein are systems, methods, and non-transitory computer-readable media to form images of one or more regions of interest in an object by processing a subset of a three-dimensional array of voxels. The regions of interest in the object can include contraband or organic or inorganic structures related to disease or injury. The images formed using systems, methods, and non-transitory computer-readable media taught herein are clear, comprehensible, and contextual.

The skilled artisan will understand that the drawings are primarily for illustrative purposes and are not intended to limit the scope of the subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar or structurally similar elements).

The foregoing and other features and advantages provided by the present disclosure will be more fully understood from the following description of exemplary embodiments when read together with the accompanying drawings, in which:.

Systems, methods, and non-transitory computer-readable media taught herein process a subset of a three-dimensional array of voxels to form an image of a region of interest (ROI) in an object. Images formed using the systems, methods, and non-transitory computer-readable media taught herein are clear, comprehensible, and contextual. Images formed in accordance with the teachings herein allow a viewer, for example, a medical professional, a security agent, or other, to select a region of interest of an object under examination and have a subset of voxels representing the ROI processed to form an image of the ROI. The systems, methods, and computer-readable media can render a two-dimensional image of the selected ROI that is interpretable by the viewer or by an image processing algorithm of a computer. The systems, methods, and non-transitory computer-readable media taught herein select the subset of voxels that represent the region of interest along a direction perpendicular to a view direction defined by the region of interest. The subset of voxels represents one or more portions of a plurality of image slices of the object.

The systems, methods, and computer-readable media taught herein are applicable to any three-dimensional array of voxels regardless of the type of x-ray system used to collect the voxel data. As taught herein, any three-dimensional array of voxels can be processed as taught herein to produce and render images of improved quality and resolution to facilitate identification of and examination of objects included therein.

As described herein, an "object" encompasses a volume that includes a physical mass and space surrounding the physical mass. The term "object" is not limited to the bounds of a particular physical object but is to be considered as a volume that may include one or more physical objects, empty space, or both. In embodiments disclosed herein related to x-ray computed tomography systems, the "object" can include, but is not limited to, an item such as a bag, bin or other container under inspection, items disposed within the bag, bin or other container, portions of the internal volume of a tunnel or scanning region through which the item passes, a human body or any portion thereof, or an animal body and any portion thereof.

As described herein, a "region of interest" can be any subset of voxels that is to be imaged from a three-dimensional array of voxels representative of the object. In particular, the term "region of interest" can include one or more items or one or more objects, empty space, or both, and is not limited to a location within an object that includes an item such as contraband or a portion of a skeletal system. In various embodiments, the region of interest can be identified by a user using an interactive user element of a computing system or can be identified based on implementation of a computer-implemented method.

As described herein, a "slice" or an "image slice" of the three-dimensional array of voxels can be a plurality of voxels having the same coordinate value along a coordinate axis (e.g., the same x-value, y-value, or z-value) of the three-dimensional array of voxels. In some embodiments, the "slice" or an "image slice" can correspond to voxels of the three-dimensional array of voxels that lie in a plane along a coordinate axis of the three-dimensional array of voxels.

As part of a wide range of image reconstruction techniques, a three-dimensional volumetric representation of an object is generated including a plurality of voxels. The plurality of voxels includes data representative of a physical property of the object such as density, effective atomic number, or electron spin relaxation times. The plurality of voxels can be visualized volumetrically or by projecting the data into two-dimensions. Methods of generating the two-dimensional projection image include collapsing the entire three-dimensional array of voxels along an axis representing a view direction or selecting a single slice of the three-dimensional array of voxels that includes some or all of the voxels that have the same value along the axis representing the view direction (i.e., an x-axis, y-axis, z-axis, or any other direction with respect to a coordinate system of the volume). An image produced by collapsing the entire three-dimensional array of voxels includes features that a human or machine viewer can intuitively recognize and understand. However, collapsing the entire three-dimensional array of voxels produces a cluttered image wherein features at different depths along the view direction overlap and become largely indistinguishable in the projection image.

Conversely, a single slice provides a cleaner image wherein the pixels correspond directly to individual physical measurements of a property of the object. However, single slice images are highly unintuitive to human and machine viewers because no additional context is provided to help the viewer identify what is shown in the image. Hence, users of imaging systems that provide single slice images require extensive training to understand how to interpret the visual information provided in a single-slice image. In addition, viewing a full object using single slices is very time-consuming due to the large number of image slices in an object. In contexts such as the security context where high throughput is essential, an unacceptable amount of time may be needed to step through single slices of the object.

Disclosed herein are methods, systems, and non-transitory computer readable media to provide intuitive and visually parsable two-dimensional projection images from a three-dimensional array of voxels representing an object. The systems, methods, and non-transitory computer-readable media of providing two-dimensional projection images described herein improve upon previous methods of generating two-dimensional images by providing cleanly separated views of features within the object while retaining high comprehensibility to a human or machine viewer.

The systems, methods, and non-transitory computer-readable media of the present disclosure select a subset of voxels from the three-dimensional array of voxels that represent a region of interest (ROI) of the object. The subset of voxels represents one or more portions of a plurality of image slices of the object and is selected along a direction perpendicular to a view direction defined by the ROI. An image of the ROI is formed by processing the subset of voxels. Images rendered using the systems, methods, and non-transitory computer-readable media described herein retain the context and intuitiveness of projection images that collapse the full volumetric dataset while providing a simple and uncluttered appearance.

In some embodiments, selection of the subset of voxels can be performed more than once to represent additional regions of interest. For example, the subset of voxels representing the ROI can be a first subset of voxels representing a first ROI. In these embodiments, the systems, methods, and non-transitory computer-readable media described herein can further select a second subset of voxels from the three-dimensional array of voxels representing a second ROI. The systems, methods, and non-transitory computer-readable media of these embodiments can further render, using the graphic unit, the image of the first ROI and the image of the second ROI on a display according to a user control. In various embodiments, the image of the second ROI is different than the image of the first ROI.

<FIG> illustrates a prior art scheme for selecting voxels to generate a projection image by selecting a single slice <NUM> from a three-dimensional array of voxels <NUM>. The projection image generated by using this conventional method consists of the object data in the single slice. Because features in the object are not always aligned with the view direction, the thin sections of features in the object that are visible in the projection image may be unrecognizable or miscategorized by a human or machine viewer due to the lack of context. As a result, the user may miss contraband in the object. An example of an image of a single slice is depicted in <FIG>.

<FIG> illustrate subsets of voxels of a three-dimensional array of voxels for use in rendering one or more projection images of portions of one or more regions of interest of an object in accordance with embodiments of the present disclosure. Each three-dimensional array of voxels <NUM>, <NUM>, <NUM> illustrated in <FIG>, respectively, can, in some embodiments, be a reconstructed volumetric dataset generated from measurement data obtained using a tomographic imaging technique. In some embodiments, the measurement data can be indicative of an interaction of an x-ray with the object. In some embodiments, a dimension of each voxel in the array of voxels can be in a range of <NUM> to <NUM>. In some embodiments, the dimension of each voxel in the array of voxels can be <NUM>. The three-dimensional array of voxels can be generated from the measurement data using one or more direct reconstruction techniques, one or more iterative reconstruction techniques, or a combination of direct and iterative reconstruction techniques. In some embodiments, the three-dimensional array of voxels can be reconstructed using a methodology that is classically complete (i.e., generated from measurement data that is pi-line complete or that is collected over a scan path that includes <NUM>° around the object). In some embodiments, the three-dimensional array of voxels can be reconstructed using a methodology that is classically incomplete (i.e., generated from measurement data that was obtained over a scan path that is less than <NUM>° around the object). In some embodiments, the three-dimensional array of voxels can include object data obtained from a magnetic resonance imaging (MRI) technique, a positron emission tomography (PET) technique, or any other suitable tomographic technique that can generate a data in the form of a three-dimensional array of voxels.

In <FIG>, the three-dimensional array of voxels <NUM> has been divided into a plurality of image slices 202a-202f. In accordance with some embodiments, the three-dimensional array of voxels <NUM> can include one or more regions of interest (ROIs) represented by a subset of voxels from the array <NUM> selected along a direction perpendicular to a view direction defined by the ROI. For example, the array of voxels <NUM> can include a first subset of voxels 230a representing a first ROI, a second subset of voxels 230b representing a second ROI, and a third subset of voxels 230c representing a third ROI. Although three subsets of voxels 230a-230c are shown in <FIG>, any suitable number of subsets can be selected from the three-dimensional array of voxels <NUM>. By processing the subset of voxels 230a-230c representing one or more ROIs, an image of one or more of the ROIs can be formed. In various embodiments, the image or images of one or more of the ROIs can be rendered using a graphic unit. In some embodiments, the image or images of the one or more of the ROIs can be processed using a computing device to detect a contraband item within the object or an object or item within a human or animal.

In some embodiments, the subset of voxels 230a-230c representing each of the ROIs can represent one or more portions of a plurality of image slices 202a-202f. For example, the subset of voxels 230a representing the first ROI can represent one or more portions of a first slice 202a and a second image slice 202b. The subset of voxels 230b representing the second ROI can represent one or more portions of a third image slice 202c and a fourth image slice 202d The subset of voxels 230c representing the third ROI can represent one or more portions of a fifth image slice 202e and a sixth image slice 202f. As shown in <FIG>, the first subset of voxels 230a and the second subset of voxels 230b can be contiguous. In some embodiments, the subset of voxels can include less than all of the voxels included in one or more of the plurality of slices 202a-202f.

In accordance with various embodiments, the subset of voxels representing each of the ROIs is selected along a direction perpendicular to the view direction <NUM> defined by the ROI. Although the view direction <NUM> is shown as parallel to a basis axis of the three-dimensional array of voxels <NUM> in <FIG>, the view direction <NUM> can be angled at any direction with respect to the orientation of the array of voxels <NUM>. In some embodiments, the coordinate axes of the three-dimensional array of voxels <NUM> can be rotated to align with the view direction <NUM>.

In accordance with various embodiments, the plurality of image slices 202a-202f can correspond to planes at different depths along a coordinate axis of the array of voxels <NUM>. In some embodiments, each of the plurality of image slices 202a-202f can include all of the voxels at each coordinate value along the coordinate axis of the array of voxels <NUM>. Although the array of voxels <NUM> has been divided into six image slices 202a-202f in <FIG>, it will be understood by one skilled in the art that the plurality of voxels can be divided into any number of image slices. For example, a three-dimensional array of voxels reconstructed from object data in a security setting can be divided into thousands of image slices.

The subset of voxels 230a-230c that represent each of the ROIs is processed in accordance with various methods to form an image of each respective ROI. For example, the subset of voxels 230a from the first image slice 202a and the second image slice 202b can represent the first ROI and can be processed to form an image of the first ROI. In some embodiments, data of the object included in the subset of voxels is summed along the view direction <NUM>. In other embodiments, data of the object included in the subset of voxels can be averaged along the view direction <NUM>.

In <FIG>, the three-dimensional array of voxels <NUM> has been divided into a plurality of image slices 302a-302f. In accordance with some embodiments, the three-dimensional array of voxels <NUM> can include one or more regions of interest (ROIs) represented by a subset of voxels from the array of voxels <NUM> selected along a direction perpendicular to a view direction <NUM> defined by the ROI. In accordance with some embodiments of the present disclosure, one or more of the ROIs can include one or more portions of a plurality of non-contiguous slices. In other words, each of the subsets of voxels 330a-330c representing the ROIs can include gaps in voxels parallel to the view direction wherein voxels included in the gaps are not included in the corresponding subset of voxels. For example, the first subset of voxels 330a representing the first ROI can include a first slice 302a and a fourth slice 302d. The second subset of voxels 330b representing the second ROI can include a second slice 302b and a fifth slice 302e. The third subset of voxels 330c representing the third ROI can include a third slice 302c and a sixth slice 302f. In some embodiments, one or more of the subsets of voxels 330a-330c can be interlaced (i.e., a portion of the second subset of voxels 330b can be interjected between portions of the first subset of voxels 330a). In some embodiments, the subset of voxels can include less than all of the voxels included in one or more of the plurality of slices 302a-302f.

In accordance with various embodiments, the subset of voxels 330a-330c representing each of the ROIs is selected along a direction perpendicular to the view direction <NUM> defined by the ROI. Although the view direction <NUM> is shown as parallel to a basis axis of the three-dimensional array of voxels <NUM>, the view direction <NUM> can be angled at any direction with respect to the orientation of the array of voxels <NUM>. In some embodiments, the coordinate axes of the three-dimensional array of voxels <NUM> can be rotated to align with the view direction <NUM>.

In <FIG>, the three-dimensional array of voxels <NUM> has been divided into a plurality of image slices 402a-402f. In accordance with some embodiments, the three-dimensional array of voxels <NUM> can include one or more regions of interest (ROIs) represented by a subset of voxels from the array of voxels <NUM> selected along a direction perpendicular to a view direction <NUM> defined by the ROI. The first subset of voxels 430a representing the first ROI can include a first image slice 402a and a second image slice 402b. The second subset of voxels 430b representing the second ROI can include the second image slice 402b, a third image slice 402c, and a fourth image slice 402d. The third subset of voxels 430c representing the third ROI can include the fourth image slice 402d, a fifth image slice 402e, and a sixth image slice 402f. In accordance with some embodiments of the present disclosure, at least one voxel of the first subset of voxels 430a representing the first ROI can also be included in the second subset of voxels 430b representing the second ROI. For example, voxels in second image slice 402b can be included in the first subset of voxels 430a and in the second subset of voxels 430b in some embodiments. Likewise, voxels in the fourth image slice 402d can be included in the second subset of voxels 430b and the third subset of voxels 430c. In accordance with various embodiments, the first subset of voxels 430a and the second subset of voxels 430b can include different numbers of voxels. For example, the first subset of voxels 430a in <FIG> can include all of the voxels in the first image slice 402a and the second image slice 402b while the second subset of voxels 430b can include all of the voxels in the second image slice 402b, the third image slice 402c, and the fourth image slice 402d. In other embodiments, the first subset of voxels 430a and the second subset of voxels 430b can include the same number of voxels.

Although the view direction <NUM> defined by the second ROI is parallel to the view direction <NUM> defined by the first ROI in <FIG>, the relationship between the two view directions is not constrained and the two view directions can be at any angle with respect to one another.

<FIG> illustrates a method of rendering a projection image of a portion of an object by omission of a subset of voxels from the three-dimensional array of voxels in accordance with some embodiments of the present disclosure. As depicted in <FIG>, a three-dimensional array of voxels <NUM> is divided into subsets of voxels 530a-530c representing the first ROI, the second ROI, and the third ROI. In some embodiments, each of the subsets of voxels 530a-530c can be projected or resampled onto a linescan geometry. For example, projection of each of the subsets of voxels 530a-530c onto a linescan geometry can include projecting from an orthographic to a perspective orientation. In the embodiment depicted in <FIG>, the first subset of voxels 530a becomes projected first ROI <NUM>, the second subset of voxels 530b becomes projected second ROI <NUM>, and the third subset of voxels 530c becomes projected third ROI <NUM>.

In some embodiments, the data of the object excluded from the subset of voxels representing an ROI can form a first two-dimensional dataset. For example, voxels excluded from projected second ROI <NUM> (i.e., the projected first ROI <NUM> and the projected third ROI <NUM> in this example) can be used to form a first two-dimensional dataset. In some embodiments, the first two-dimensional dataset is formed by summing the data along the view direction <NUM>. For example, data in the projected first ROI <NUM> and the projected third ROI <NUM> can be summed to create the first two-dimensional dataset <NUM>.

In some embodiments, a second two-dimensional dataset <NUM> can be formed by using the full three-dimensional array of voxels. For example, the second two-dimensional dataset <NUM> can be generated from measurement data obtained using a line-scan imaging technique or can be a full projection image along the view direction <NUM> including the entire array of voxels <NUM>. In accordance with various embodiments, a projection image of the ROI can be generated by subtracting the first two-dimensional dataset from the second two-dimensional dataset. For example, the first two-dimensional dataset <NUM> can be subtracted from the second two-dimensional dataset <NUM> to create a projection image <NUM> of the second ROI 530b. In some embodiments, images created using a line-scan imaging technique can be of higher resolution than projection images formed from voxels of an array of voxels <NUM>. Subtraction of the first two-dimensional dataset from the second two-dimensional dataset as described herein can provide the ability to isolate an ROI in a higher resolution image than would be possible by manipulating only the three-dimensional array of voxels <NUM>.

In accordance with various embodiments of the present disclosure, reconstruction of the three-dimensional array of voxels representing an object can be a separate and distinct process from segmentation of the array of voxels to based on specific criteria. In some embodiments, a user can select and review one or more ROIs continuously while viewing volumetric images of the object as described in greater detail below. In some embodiments, segmentation of the array of voxels can occur automatically after reconstruction but before algorithmic discovery of appropriate ROIs.

The volume of the object can be less than the total volume represented in the three-dimensional array of voxels <NUM>, <NUM>, <NUM>, <NUM>. In some embodiments, segmentation of the three-dimensional array of voxels can occur to identify an object or item represented within the array of voxels. In some embodiments, an image slice can be determined that denotes an edge of the object. For example, the image slice can be identified that is at the edge of a sub-volume of the array of voxels <NUM> that encompasses between <NUM>% and <NUM>%, or more preferably between <NUM>% and <NUM> %, or most preferably between <NUM>% and <NUM>% of a total sum of the data of the object in the three-dimensional array of voxels <NUM>, <NUM>, <NUM>, <NUM>. In some embodiments, the data of the object can be mass density, and the image slice can be identified that is at the edge of a sub-volume of the array of voxels <NUM>, <NUM>, <NUM>, <NUM> that includes <NUM>% or more of the total mass found in the three-dimensional array of voxels. In embodiments where the image slice that is at the edge of the object is determined, voxels beyond that slice can be excluded from any selected subset of voxels. By excluding voxels that do not represent data of the object (i.e., that represent empty space), computational overhead can be reduced without reducing image quality. In addition, empty voxels can include errors that occur during reconstruction of the array of voxels <NUM>, <NUM>, <NUM>, <NUM>. By excluding the empty voxels, the error rate can be reduced and the image quality can be increased.

A method of forming an image of an object is depicted in <FIG> in accordance with various embodiments. Performance of the method <NUM> receives, using at least one processing unit, a three-dimensional array of voxels (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) representing an object in Step <NUM>. In step <NUM>, a subset of voxels (230a-230c, 330a-330c, 430a-430c) is selected from the array representing a region of interest (ROI) of the object using the at least one processing unit. The subset of voxels represents one or more portions of a plurality of image slices (202a-202f, 302a-302f, 402a-402f) of the object. The subset of voxels is selected along a direction perpendicular to a view direction defined by the ROI. In some embodiments, the entire object can be automatically partitioned into ROIs of a predetermined size. In such embodiments, each subset of voxels representing an ROI can include one or more portions of between <NUM> and <NUM> image slices. In step <NUM>, an image is formed of the ROI by processing the subset of voxels. In some embodiments, step <NUM> renders, using a graphic unit, the image of the ROI.

A computer-implemented method is depicted in <FIG> in accordance with some embodiments. Performance of the computer-implemented method <NUM> renders a GUI <NUM> on a display to display an image of an object in step <NUM>. In step <NUM>, input is received, via one or more graphical user interface elements of the GUI, to identify a region of interest of the image of the object. In step <NUM>, a subset of voxels from a three-dimensional array of voxels representing an ROI of the object is processed to form an image of the ROI in response to receipt of the identification of the ROI. The subset of voxels represents one or more portions of a plurality of image slices of the object. The subset of voxels is selected along a direction perpendicular to a view direction defined by the region of interest. In step <NUM>, the image of the ROI is rendered in the GUI window. In step <NUM>, input is received via the GUI to manipulate the image of the ROI. An example of a computational device for performing the computer implemented-method is illustrated in <FIG>.

<FIG> and <FIG> illustrate exemplary windows of a graphical user interface <NUM> according to various embodiments of the disclosure taught herein. The graphical user interface (GUI) <NUM> can include one or more windows <NUM>, <NUM>, <NUM>. In <FIG>, the GUI <NUM> includes a first window <NUM> and a second window <NUM>. The first window <NUM> can be rendered to display multiple ROI images of the object as taught herein. The second window <NUM> can render a resizable view <NUM> of an ROI image selected from first window <NUM>.

In some embodiments, the image of the object is a volumetric image. In some embodiments, the volumetric image can be divided into regions of interest as discussed above in relation to <FIG>. In some embodiments, the ROIs can be rendered individually one at a time or rendered individually as part of a montage of images representing a plurality of ROIs in the object of interest. The montage of images may be rendered to appear in a stacked relationship with the image of each ROI individually selectable by a user using a pointing device, by scrolling or manipulating a wheel on the pointing device, or by interaction with a touchscreen of the display device. By examining the separated ROIs, the user can preliminarily identify contraband <NUM> as it is not obscured by surrounding items <NUM> in the object. Identification or selection of the ROI by the user can cause the computer-implemented method to process a subset of voxels representing that ROI to form an image of the ROI. The projection image of the ROI can be displayed in the second window <NUM>.

As depicted in the first window <NUM>, four ROI images 730a-730d are shown with separation between them for improved visibility. In some embodiments, the multiple ROI images 730a-730d can rotate before the viewer upon selection of a GUI element, for example, view rotation arrows 735a, 735b. In some embodiments, the user can use rotation view arrows 735a, 735b to rotate one or more of the ROI images 730a-730d in the first window <NUM> individually or can rotate some or all of the ROI images 730a-730d as a group. In some embodiments, the user can use a slider bar 735c to bring different ROI images into view or to select an ROI image for further action. The slider bar 735c allows the user to scroll the ROI images 730a-730d up or down in a vertical direction. The slider bar 735i allows the user to scroll the ROI images 730a-730d from side-to-side in a horizontal direction. In some embodiments, the GUI <NUM> can provide a visual indicator <NUM> of the ROI corresponding to the resizable ROI image <NUM> that is rendered in the second window <NUM>. The visual indicator <NUM> can be an arrow rendered on the display. To highlight an ROI to the user, differences in the display contrast including coloration, shading, or line thickness, lines delineating the edges of the ROI, or any other suitable method can be used. In some embodiments, the user can select the location of the ROI in the object.

In some embodiments, the user uses one or more GUI elements 735a-735i of the GUI <NUM> to identify, review, and manipulate one or more of the ROIs 730a-730d in the first window <NUM> or the second window <NUM>. These GUI elements can include, but are not limited to, slider bars, view rotation arrows, magnification buttons, demagnification buttons, image size reset buttons, menus, buttons, gesture elements responsive to a gesture, or mouse control elements. In some embodiments, the mouse control element can include input from rotation of a mouse wheel. In some embodiments, the GUI elements can be configured to allow the user to select a dimension or location of the ROI. For example, the GUI element can allow the user to expand or contract the ROI. In some embodiments, the GUI <NUM> can provide a magnification button 735d and a demagnification button 735e to allow increase or decrease in the magnification of the resizable ROI image <NUM>. Similarly, the GUI <NUM> can provide a rotation button 735f to allow the viewer to rotate the orientation of the resizable ROI image <NUM>.

<FIG> depicts another example of multiple windows of the GUI <NUM>. As depicted in <FIG>, the GUI <NUM> includes the first window <NUM>, the second window <NUM>, and a third window <NUM>. In accordance with various embodiments, the first window <NUM>, second window <NUM>, and third window <NUM> can each include a projection image of the object. In some embodiments, the rendered projection images <NUM>, <NUM>, <NUM> in each window <NUM>, <NUM>, <NUM> are formed along different view directions. In some embodiments, one or more of the projection images <NUM>, <NUM> are full projection images formed by collapsing the entire three-dimensional array of voxels. In some embodiments, the one or more projection images can be formed along perpendicular view directions. The object depicted in <FIG> includes contraband <NUM> and surrounding items <NUM>. The use of multiple projection images along different view directions can increase the likelihood that the user will preliminarily identify contraband <NUM>.

In some embodiments, a side projection view <NUM> and an end projection view <NUM> of the object can be shown in the first window <NUM> and the third window <NUM>, respectively. In some embodiments, the side projection view <NUM> and the end projection view <NUM> can be generated by collapsing the full three-dimensional array of voxels. The complementary views of the object seen in the side projection view <NUM> and the end projection view <NUM> can help the user preliminarily identify contraband <NUM> items among surrounding objects <NUM>. In some embodiments, an ROI can be depicted in the side projection view <NUM> and the end projection view <NUM> between moveable GUI line elements <NUM> and <NUM>, respectively. A resizable ROI image <NUM> from between the movable GUI line elements <NUM> and <NUM> can be formed as taught herein and can be displayed in the second window <NUM>.

If the user preliminarily identifies contraband <NUM>, the user can adjust the ROI to focus on the contraband <NUM> and at least partially exclude surrounding objects <NUM> to produce a suitable projection image including the contraband <NUM>. In various embodiments, the ROI can be visualized in the projection views <NUM>, <NUM> using differences in display contrast such as coloration, shading, or line thickness or by using lines delineating the edges of the ROI. In some embodiments, a line <NUM> is provided to separate the first window <NUM> and the third window <NUM>. In some embodiments, the line <NUM> can be moved by the user to adjust the relative size of the first window <NUM> and the third window <NUM>. In some embodiments, the GUI <NUM> dynamically resizes the side projection image <NUM> and the end projection image <NUM> as the user slides the dividing line <NUM> from side-to-side.

In some embodiments, the user can use the moveable elements <NUM>, <NUM> to select a dimension of the ROI. For example, the user can use a pointing device in the one or more projection images to drag the moveable GUI line elements <NUM>, <NUM> to change a dimension of the ROI to create a new ROI. In turn, the processing unit can select a subset of voxels representing the new ROI and can form and render an image <NUM> of the new ROI in the second window <NUM>. In some embodiments, the GUI <NUM> can render some or all of the side projection image <NUM>, end projection image <NUM>, and ROI image <NUM> in response to selections of dimension of the ROI made by the user. In some embodiments, the user can use view rotation arrows 735a to rotate one or more of the side projection image <NUM> and the end projection image <NUM> in the first window <NUM>. In some embodiments, the GUI <NUM> can provide the magnification button 735d and the demagnification button 735e to allow increase or decrease, respectively, in the magnification of the resizable ROI image <NUM>. Similarly, the GUI <NUM> can provide the rotation button 735f to allow the viewer to rotate the orientation of the resizable ROI image <NUM>.

In some embodiments, the GUI <NUM> can enable a user to tag a region within the image of the ROI that corresponds to an item of interest. For example, a user might identify contraband <NUM> within an ROI and wish to tag the location of the contraband <NUM> within the object. In some embodiments, the tagged region can be identified by the user by dragging a bounding box <NUM> to define the tagged region. Once the tagged region has been defined, the GUI <NUM> in some embodiments can render, using a graphic unit, an image of the tagged region. In some embodiments, the GUI <NUM> can save, in a memory, data related to the location of the tagged region within the object.

To evaluate the imaging improvements taught herein, the systems, methods, and non-transitory computer-readable media as taught herein were used to generate images of the object that includes multiple items including contraband <NUM>. The object was scanned using an x-ray computed tomography (CT) system with a rotating gantry as described below. Measurement data collected by the CT system was reconstructed into a three-dimensional array of voxels.

<FIG> were generated from the same three-dimensional array of voxels along the same view direction. <FIG> depict a conventional full projection image and a conventional single-slice projection image of the object, respectively. <FIG> depicts an image of an ROI including the contraband <NUM> rendered in accordance with the principles taught herein.

In <FIG>, a full projection image <NUM> was generated by summing the data values along the view direction for all voxels in the three-dimensional array of voxels. By summing data values for the entire array of voxels, items included in the object that are "above" or "below" one another along the view direction overlap in the resulting projection image. Thus, the resulting image is cluttered, and individual items included in the object require significant time, attention, and training for a user to identify. The image of <FIG> is inadequate when used in a security context because of the operational context of reviewing many passenger bags under time pressure.

<FIG> is a slice image <NUM> representing a single-slice projection through the object as described above with reference to <FIG>. The image was generated by selecting voxels from the array of voxels that all lie in a plane perpendicular to the view direction. By selecting voxels from a single image slice of the array of voxels, items included in the object are often unidentifiable because their shape in the image is not necessary indicative of their true shape. As a result, a human viewer requires significant time, attention, and training when viewing images representing single slices of the object. The slice image <NUM> is inadequate when used in a security environment because of the operational context of reviewing many objects, for example passenger bags, freight, and the like, under time constraints. In addition, the array of voxels in this instance can be represented by hundreds of image slices. Stepping through hundreds of images for each object would be excessively burdensome for a viewer in a security environment.

<FIG> is an ROI image <NUM> formed by processing a selected subset of voxels representing a plurality of image slices of the array of voxels representing the object as discussed above in relation to <FIG>. For the ROI image <NUM>, the subset of voxels represents approximately twenty-four image slices. The subset of voxels was processed by summing the data of the object in the direction parallel to the view direction. As shown, the full outline of the contraband <NUM> is readily visible in ROI image <NUM> and would immediately be recognizable to a machine or human viewer.

ROI image <NUM> and slice image <NUM> are images of the same article of contraband <NUM>. Slice image <NUM> represents a single slice of data through the object. ROI image <NUM> represents an ROI of the object formed from a plurality of slices of data through the object. Image <NUM> is formed from a selected subset of voxels representing an ROI and includes voxels from about twenty-five image slices.

<FIG> is a block diagram of an exemplary computing device <NUM> that may be used to implement exemplary embodiments of the image reconstruction systems, methods, and non-transitory computer-readable media described herein. Descriptions and elements of the computing device <NUM> below may be applicable to any computing device described above with reference to previous embodiments. The computing device <NUM> includes one or more non-transitory computer-readable media for storing one or more computer-executable instructions or software for implementing exemplary embodiments. The non-transitory computer-readable media may include, but are not limited to, one or more types of hardware memory, non-transitory tangible media (for example, one or more magnetic storage disks, one or more optical disks, one or more flash drives, one or more solid state disks), and the like. For example, memory <NUM> included in the computing device <NUM> may store computer-readable and computer-executable instructions or software for implementing exemplary embodiments of the imaging system <NUM>. The computing device <NUM> also includes the configurable or programmable processing unit <NUM> and associated core(s) <NUM> and may include one or more additional configurable or programmable processor(s) <NUM>' and associated core(s) <NUM>' (for example, in the case of computer systems having multiple processors or cores), for executing computer-readable and computer-executable instructions or software stored in the memory <NUM> and other programs for controlling system hardware. Processor <NUM> and processor(s) <NUM>' may each be a single core processor or multiple core (<NUM> and <NUM>') processor.

Virtualization may be employed in the computing device <NUM> so that infrastructure and resources in the computing device may be shared dynamically. A virtual machine <NUM> may be provided to handle a process running on multiple processors so that the process appears to be using only one computing resource rather than multiple computing resources. Multiple virtual machines may also be used with one processor.

Memory <NUM> may include a read-only memory or random access memory, such as DRAM, SRAM, EDO RAM, and the like. Memory <NUM> may include other types of memory as well, or combinations thereof. In some embodiments, the memory <NUM> can be used to store measurement data <NUM> or the three-dimensional array of voxels <NUM>, <NUM>, <NUM>, <NUM>.

A user may interact with the computing device <NUM> through the display <NUM>, such as a computer monitor, onto which the graphic unit <NUM> may display one or more GUIs <NUM> provided in accordance with exemplary embodiments. The computing device <NUM> may include other I/O devices for receiving input from a user, for example, a keyboard or any suitable multi-point touch interface <NUM>, a pointing device <NUM> (e.g., a mouse), a microphone <NUM>, or an image capturing device <NUM> (e.g., a camera or scanner). The multi-point touch interface <NUM> (e.g., keyboard, pin pad, scanner, touch-screen, etc.) and the pointing device <NUM> (e.g., mouse, stylus pen, etc.) may be coupled to the display <NUM>. The computing device <NUM> may include other suitable conventional I/O peripherals.

The computing device <NUM> may also include one or more storage devices <NUM>, such as a hard-drive, CD-ROM, or other computer readable media, for storing data and computer-readable instructions or software that implement exemplary embodiments of the imaging system <NUM>. For example, the storage <NUM> can store one or more implementations of direct reconstruction executable codes <NUM>, iterative reconstruction executable codes <NUM>, or image processing executable codes <NUM> that are further discussed above in connection with <FIG>. Exemplary storage device <NUM> may also store one or more databases for storing any suitable information required to implement exemplary embodiments. For example, exemplary storage device <NUM> can store one or more databases <NUM> for storing information, such as transport system speed, items scanned, number of alarm triggers, sensor information, system geometry, x-ray source calibration, time since last system maintenance, lifetime usage, or any other information to be used by embodiments of the system <NUM>. The databases may be updated manually or automatically at any suitable time to add, delete, or update one or more data items in the databases.

The direct reconstruction code <NUM> includes executable code and other code to cause the processing unit <NUM> to implement one or more of the direct reconstruction techniques taught herein. The iterative reconstruction code <NUM> includes executable code and other code to cause the processing unit <NUM> to perform one or more of the iterative reconstruction methodologies taught herein. The image processing code <NUM> includes executable code and other code to cause the processing unit <NUM> to form or render an image of the ROI of the object as taught herein, for example, as illustrated and described with reference to <FIG>. Although viewed as separate structures in storage <NUM>, one or more of the direct reconstruction code <NUM>, the iterative reconstruction code <NUM>, and the image processing code <NUM> may be implemented as a single module or routine.

The computing device <NUM> can include a network interface <NUM> that can be used to transmit or receive data, or communicate with other devices, in any of the exemplary embodiments described herein. Network interface <NUM> can be configured to interface via one or more network devices <NUM> with one or more networks, for example, Local Area Network (LAN), Wide Area Network (WAN) or the Internet through a variety of connections including, but not limited to, standard telephone lines, LAN or WAN links (for example, <NUM>, T1, T3, 56kb, X. <NUM>), broadband connections (for example, ISDN, Frame Relay, ATM), wireless connections (Wi-Fi, <NUM>, <NUM>, Bluetooth®), controller area network (CAN), or some combination of any or all of the above. In exemplary embodiments, the computing device <NUM> can include one or more antennas <NUM> to facilitate wireless communication (e.g., via the network interface) between the computing device <NUM> and a network. The network interface <NUM> may include a built-in network adapter, network interface card, PCMCIA network card, card bus network adapter, wireless network adapter, USB network adapter, modem or any other device suitable for interfacing the computing device <NUM> to any type of network capable of communication and performing the operations described herein. Moreover, the computing device <NUM> may be any computer system, such as a workstation, desktop computer, server, laptop, handheld computer, tablet computer (e.g., the IPAD™ tablet computer), mobile computing or communication device (e.g., the IPHONE™ communication device), internal corporate devices, or other form of computing or telecommunications device that is capable of communication and that has sufficient processor power and memory capacity to perform the operations described herein.

The computing device <NUM> may run any operating system <NUM>, such as any of the versions of the Microsoft® Windows® operating systems, the different releases of the Unix and Linux operating systems, any version of the MacOS® for Macintosh computers, any embedded operating system, any real-time operating system, any open source operating system, any proprietary operating system, or any other operating system capable of running on the computing device and performing the operations described herein. In exemplary embodiments, the operating system <NUM> may be run in native mode or emulated mode. In an exemplary embodiment, the operating system <NUM> may be run on one or more cloud machine instances.

As discussed above, the formation of an ROI image as taught herein from a subset of voxels in an array of voxels is not dependent on the type or configuration of the system that collected the measurement data from which the array of voxels is derived. Applicable systems can include medical systems, cargo scanning systems, or any other imaging modality that generates a three-dimensional array representation of an object. The concepts taught herein to select and render an image of an ROI of an object can be applied across known systems with little or no change to the detectors and radiation sources. A range of exemplary systems will now be described that are compatible with teachings presented herein.

Imaging systems in accordance with embodiments of the present disclosure can include an imaging apparatus to acquire measurement data of the object. The imaging systems can further include a programmable processing unit having a central processing unit, communicatively coupled to a memory.

The imaging apparatus in some embodiments can be an x-ray CT system. The x-ray CT system can have a moving x-ray source or a stationary x-ray source configured to irradiate at least a portion of the object. In some embodiments, the moving x-ray source can be disposed on a rotating gantry.

<FIG> illustrates an exemplary imaging system <NUM> for forming and rendering projection images of at least a portion of an object <NUM>, according to one embodiment of the present disclosure. The imaging system <NUM> includes an imaging chamber <NUM>, a transport system <NUM> to transport the object <NUM>, a computing device <NUM>, an x-ray source <NUM>, and a detector <NUM>. The imaging chamber encloses a passageway <NUM>. The computing device <NUM> can include a display <NUM>, an input device <NUM>, a processing unit <NUM>, and a graphic unit <NUM>. The computing device <NUM> can be used to render images of one or more ROIs as taught herein, the GUI <NUM>, and other interfaces on the display <NUM> using the graphic unit <NUM>.

The transport system <NUM> can be configured to transport the object <NUM> through at least a portion of the passageway <NUM> of the imaging chamber <NUM>. In accordance with various embodiments, the transport system <NUM> can include an object transport mechanism such as, but not limited to, a conveyor belt <NUM>, a series of rollers, or a cable that can couple to and pull an object <NUM> into the imaging chamber <NUM>. The transport system <NUM> can be configured to transfer the object <NUM> into the passageway <NUM> of the imaging chamber <NUM> at a range of speeds. The transport system <NUM> can transport the object <NUM> at any speed that allows collection of measurement data of the object <NUM>.

The x-ray source <NUM> can be configured to emit a conical beam of x-ray radiation (or gamma rays, or other radiation) at a plurality of points along a trajectory around the conveyor <NUM> on a scan path <NUM> relative to a direction of transport of the object <NUM>, to irradiate at least a portion of the object <NUM>. In some embodiments, the trajectory around the conveyor <NUM> on the scan path <NUM> relative to the direction of transport of the object <NUM> can be less than or greater than <NUM>°. In some embodiments, the source <NUM> can emit gamma rays. The detector <NUM> can be configured to detect measurement data indicative of an interaction of the x-ray radiation with the portion of the object <NUM>. The detector <NUM> is disposed relative to the x-ray source <NUM> to detect the measurement data along the scan path <NUM>. In some embodiments, the source <NUM> and detector <NUM> can have a fixed spatial relationship and may rotate about a longitudinal axis of the imaging system <NUM> as, for example, on a gantry. In some embodiments, one or more sources <NUM> and detectors <NUM> can be fixed with respect to the transport system <NUM>. In some embodiments, the positions of the x-ray source <NUM> and detector <NUM> can be fully known as a function of time during scanning of the object <NUM>.

The computing device <NUM> includes at least one processing unit <NUM> including at least one central processing unit (CPU). The computing device <NUM> can be configured to receive measurement data acquired by the detector <NUM>. The processing unit <NUM> is programmable to execute processor-executable instructions such as image processing executable code to form projection images of portions of the object <NUM> as described in greater detail above.

The central processing unit is programmable to compute a reconstructed three-dimensional array of voxels representative of the object <NUM> by applying at least one iteration of an iterative reconstruction to the measurement data to derive the reconstructed three-dimensional array of voxels. In some embodiments, the programmable processing unit can execute image processing code <NUM> to receive the three-dimensional array of voxels representing the object upon execution of processor-executable instructions. Execution of the image processing code <NUM> allows a user to select an ROI of the object from a projection image. Based on the selected ROI, the image processing code <NUM> selects a subset of voxels from the array of voxels representative of the selected ROI. The subset of voxels represents one or more portions of a plurality of image slices of the object and is selected along a direction perpendicular to a view direction defined by the ROI. Execution of the image processing code <NUM> can form an image of the ROI by processing the subset of voxels. The computing device <NUM> and the processing unit <NUM> are discussed in greater detail with respect to <FIG>.

The computing device <NUM> including the processing unit <NUM> can be configured to exchange data, or instructions, or both data and instructions, with at least one of the other components of the imaging system <NUM> wirelessly or via one or more wires or cables <NUM>. As an example, the computing device <NUM> including the processing unit <NUM> can communicate with the x-ray source <NUM> or the detector <NUM> to control the operation of each and receive measurement data from the detector <NUM>. The computing device <NUM> including the processing unit <NUM> can receive measurement data that is representative of a volume of the object <NUM> and can be configured or programmed to apply at least one iteration of an iterative reconstruction to the measurement data to derive the three-dimensional array of voxels. In some embodiments, the computing device <NUM> can be configured to receive detector orientation data that correlates to the instantaneous location of the detector <NUM> with respect to the object <NUM>. Detector orientation data can be provided by location sensors located at or near the source <NUM>, detector <NUM>, or scan path <NUM> or can be calculated based upon other geometrical quantities of the imaging system <NUM>. In some embodiments, the detector orientation data can be encoded directly into the measurement data.

The graphic unit <NUM> can be configured to render an image of an ROI, for example, ROI image <NUM> from the three-dimensional array of voxels <NUM>, <NUM>, <NUM>, <NUM> on the display <NUM>. The graphic unit <NUM> can render a user interface on the display <NUM> to allow a user of the imaging system <NUM> to interact with the user interface of the computing device <NUM> with an input device <NUM>. In some embodiments, the user interface is a GUI <NUM> as described, for example, in relation to <FIG> and <FIG>. The input device <NUM> can be a keyboard, a mouse, a trackball, a touchpad, a stylus, a touchscreen of the display <NUM> or any other suitable device that allows a user to interface with the computing device. In some embodiments, the GUI <NUM> can be rendered on a touchscreen to allow a user to input information or data via the touchscreen.

The imaging chamber <NUM> may be made of appropriate metal or plastic materials that allow the desired spacing and orientation of the x-ray source <NUM> and the detector <NUM> relative to the object <NUM>. In some embodiments, the imaging chamber <NUM> may include radiation stopping or absorbing material such as lead.

The object <NUM> to be imaged can enter the imaging chamber <NUM> through the passageway <NUM>. The size of the passageway <NUM> may be of any shape that meets application-specific requirements. For example, the passageway <NUM> may be configured with a passageway sized to allow the transport of hand-carry luggage, checked luggage, cargo, shipping containers, or any other type of object. The passageway <NUM> may be configured with any geometric conformation. As non-limiting examples, the passageway <NUM> can have a circular cross-section, a square cross-section, a rectangular cross-section, a hexagonal cross-section, an oval cross-section, or other polygonal-shaped cross-section. In another example, passageway <NUM> can have an irregularly-shaped cross-section.

The imaging chamber <NUM> can house one or more x-ray sources <NUM> and detectors <NUM>. In accordance with various embodiments, the x-ray source <NUM> may be an x-ray source or a gamma ray source. The x-ray source(s) <NUM> can be configured to emit a cone-beam of radiation to interact with the object <NUM>, and the detectors <NUM> can be configured to detect radiation indicative of an interaction of the radiation with any portion of the object. As a non-limiting example, the detector <NUM> can detect attenuated radiation that has passed through a portion of the object <NUM>. In some embodiments, the x-ray source <NUM> and detector <NUM> can move cooperatively along a circular scan path that may be defined relative to the motion of an object <NUM> to form a helical cone beam. For example, the scan path may be a partial or complete circle of constant radius where the object <NUM> travels along a line passing through a central portion of the circle. The x-ray source <NUM> of some embodiments can include a high-energy electron beam and an extended target or array of targets. In some embodiments, imaging systems as taught herein can have more than one source and detector.

In some embodiments, the detector <NUM> may be configured with multiple detector elements in a detector array.

The processing unit <NUM> can be configured to generate the three-dimensional array of voxels representing the object from the radiation detected by the detectors <NUM> using any suitable image reconstruction methodology. Examples of direct reconstruction techniques that may be used to reconstruct the three-dimensional array of voxels in some embodiments include a filtered back-projection methodology, an analytical cone-beam methodology, an approximate cone-beam methodology, a Fourier reconstruction methodology, an extended parallel back-projection methodology, a filtered back-projection with dynamic pitch methodology, a pi-line-based image reconstruction methodology, a Feldkamp-type reconstruction methodology, a tilted-plane Feldkamp-type reconstruction methodology, or any other direct reconstruction technique that meets application-specific requirements.

Iterative reconstruction techniques may also be employed in the system <NUM> to reconstruct the three-dimensional array of voxels representing the object. Examples of iterative reconstruction techniques include a simultaneous algebraic reconstruction technique (SART), a simultaneous iterative reconstruction technique (SIRT), an ordered subset convex technique (OSC), ordered subset maximum likelihood methodologies, an ordered subset expectation maximization (OSEM) methodology, an adaptive statistical iterative reconstruction technique (ASIR) methodology, a least squares QR methodology, an expectation maximization (EM) methodology, an OS-separable paraboloidal surrogates technique (OS-SPS), an algebraic reconstruction technique (ART), a Kacsmarz reconstruction technique, or any other iterative reconstruction technique or methodology that meets application-specific requirements. In some embodiments, a sparse matrix or a compressed sensing technique can be used to increase the speed of the reconstruction.

In the implementation of an iterative reconstruction technique, an initial state is defined before successive iterative steps are performed. When initialized using an empty or uniform set, an iterative reconstruction technique may perform many iterations before achieving convergence. Each iteration step is computationally intensive, so conducting many iteration steps can unacceptably increase the total time for data reconstruction. Reducing the numbers of iterations to achieve a solution can greatly increase the speed and efficiency of the image reconstruction computation. In accordance with various embodiments, the process of iterative reconstruction can be initialized using the output from a direct reconstruction technique including, but not limited to, a filtered back-projection methodology. The use of output from a direct reconstruction technique can significantly reduce the number of iterations to reach convergence and speed up total processing time.

In accordance with various embodiments, measurements obtained from a detector <NUM> may be used by the processing unit <NUM> to reconstruct a three-dimensional (i.e., volumetric) array of voxels representing properties of the object <NUM>. Data included in the three-dimensional array of voxels can represent one or more properties of the object <NUM> being imaged, which may be under inspection to identify contraband <NUM>. For example, the radiation emitted by the x-ray source <NUM> may attenuate as it passes through a portion of the object <NUM> before impinging on a detector <NUM>. This attenuation is proportional to the density of the portion of the object <NUM> through which it traveled. Accordingly, data in the three-dimensional array of voxels can represent information about the density of the portion of the object. In another embodiment, radiation at two different energy levels may be directed such that they pass through a portion of the object <NUM>. The ratio of the attenuation between beams at two different energy levels can provide information about the atomic number or elemental composition of the portion of the object <NUM>. The system <NUM> according to the principles taught herein may be configured to compute data in the three-dimensional array of voxels corresponding to the density, or atomic number, or both density and atomic number properties, of a portion of the volume of the object <NUM>. In various embodiments, measurement data or reconstructed images or representations may be stored and retrieved for analysis at a later date or may be displayed to a user on the display <NUM>. In some embodiments, the measurement data collected at the detector <NUM> may be interpolated onto a virtual array or interpolation may be used to modify or replace data values associated with malfunctioning or missing detector positions.

<FIG> depict systems for acquiring measurement data of the object and generating images of ROIs of the object in accordance with the teachings herein. In these embodiments, the object <NUM>' can be a biological organism. The systems of <FIG> can generate and process measurement data to create three-dimensional volumetric or two-dimensional projection images of an ROI included in the object <NUM>'. In some embodiments, the ROI can include an organic or inorganic structure within the biological organism.

<FIG> depicts a system <NUM>' that includes a source <NUM>', a detector <NUM>', and the computing device <NUM>. The computing device can include the graphic unit <NUM>, the processing unit <NUM>, the display <NUM>, and the input device <NUM>. The source <NUM>' can emit radiation that can interact with the object <NUM>' and then be detected by the detector <NUM>'. The detector <NUM>' can generate measurement data based on the received radiation that is indicative of the interaction of the radiation with the object <NUM>'.

In some embodiments, the source <NUM>' can be an x-ray source similar to the system described above with reference to <FIG>. For example, the source <NUM>' can be the x-ray source of a medical computed tomography (CT) system. In some embodiments, the source <NUM>' can emit other forms of penetrating or non-penetrating radiation such as gamma rays, microwave radiation, infrared radiation, visible radiation, ultraviolet radiation, or any other suitable form of radiation.

The source <NUM>' can be configured to emit a cone-beam of radiation to interact with the object <NUM>', and the detector(s) <NUM>' can be configured to detect radiation indicative of an interaction of the radiation with any portion of the object. As a non-limiting example, the detector <NUM>' can detect attenuated radiation that has passed through a portion of the object <NUM>'. In some embodiments, the source <NUM>' and detector <NUM>' can move cooperatively along a circular scan path that may be defined relative to the motion of an object <NUM>' to form a helical cone beam. For example, the scan path may be a partial or complete circle of constant radius where the object <NUM>' travels along a line passing through a central portion of the circle. The x-ray source <NUM>' of some embodiments can include a high-energy electron beam and an extended target or array of targets. In some embodiments, imaging systems as taught herein can have more than one source and detector.

In some embodiments, the detector <NUM>' may be configured with multiple detector elements in a detector array. In some embodiments, the detector <NUM>' can be configured to detect radiation backscattered or reflected from the object <NUM>' rather than radiation transmitted through the object <NUM>'.

<FIG> depicts a system <NUM>" including a source <NUM>", a detector <NUM>", and the computing device <NUM>. The computing device can include the graphic unit <NUM>, the processing unit <NUM>, the display <NUM>, and the input device <NUM>. In accordance with some embodiments, the source <NUM>" can be located within the object <NUM>".

In some embodiments, the source <NUM>" can be configured to emit a variety of fundamental particles and waves including alpha particles, beta particles, gamma particles, positrons, muons, electrons, or photons from within the object <NUM>". In some embodiments, the source <NUM>" can emit a first particle or wave that can convert into a second particle or wave that is then detected by the detector <NUM>". For example, the source <NUM>" can include radionuclides that emit positrons as in positron emission tomography. The positrons can recombine with electrons to release gamma rays that are then detected by the detector <NUM>". In another embodiment, the source <NUM>" can emit light that is converted by interaction with the object <NUM>" into an acoustic signal as in photo- or optoacoustic imaging. The detectors <NUM>" in this embodiment can be ultrasonic transducers that receive the acoustic signal to produce measurement data.

In some embodiments, the detector <NUM>" may be configured with multiple detector elements in a detector array. In some embodiments, multiple detectors <NUM>" in an array can be placed around the object <NUM>" to receive particles or waves emitted directly or indirectly by the source <NUM>" within the object <NUM>". In some embodiments, the computing device <NUM> can use techniques such as time-of-flight to determine a position of the source <NUM>" within the object <NUM>" based on measurement data received at different times by the detectors <NUM>" in the detector array.

<FIG> depicts a system <NUM>'" including a source <NUM>"', a detector <NUM>"', and the computing device <NUM>. The computing device can include the graphic unit <NUM>, the processing unit <NUM>, the display <NUM>, and the input device <NUM>. In accordance with some embodiments, the source <NUM>‴ can stimulate or perturb a portion of the object <NUM>‴ in a way that can be detected by the detector <NUM>‴.

In some embodiments, the source <NUM>‴ can be an electromagnet or permanent magnet. In these embodiments, the source <NUM>‴ can operate to stimulate or perturb all or a portion of the object <NUM>‴ by applying a large magnetic field to the object to excite or align the nuclear spins of constituent components of the object <NUM>‴ such as hydrogen atoms. The source <NUM>‴ can apply a magnetic field that varies in space and time in some embodiments.

In some embodiments, the detector <NUM>‴ may be configured with multiple detector elements in a detector array. The detector <NUM>‴ can include magnetic coils that can detect radio frequency signals emitted by excited constituents of the object <NUM>‴ such as hydrogen atoms. In some embodiments, the computing device <NUM> can control the operation of the source <NUM>‴ and detector <NUM>‴ to correlate measurement data with spatial locations within or around the object <NUM>‴.

As described above, the source and detector of systems to generate measurement data according to embodiments taught herein can have a number of relationships. In some embodiments, the source and detector can have a fixed spatial relationship and, for example, may rotate about a longitudinal axis of the imaging system as, for example, on a gantry. In some embodiments, one or more sources and detectors can be fixed in space or relative to the motion of an object during imaging.

An example rotating gantry according to various embodiments is depicted in <FIG>. The gantry <NUM> includes an opening or central bore <NUM> through which objects may pass in connection with a transport system as discussed above with reference to <FIG>. The x-ray source <NUM> may be located on the gantry <NUM>, and the detector array <NUM> may be located substantially opposite the x-ray source <NUM> across the opening.

In some embodiments, a coating such as a metal foil <NUM>, <NUM>, <NUM> can be overlaid on one or more elements of the detector array <NUM>. The coated elements <NUM>, <NUM>, <NUM> may be sensitive to different radiation energy than the exposed elements. With these secondary energy detector elements interpolated within the main detector array <NUM>, embodiments taught herein may be capable of measuring volume properties such as atomic number or elemental composition. The introduction of secondary energy detector elements can leave gaps in the dataset when performing a volumetric data reconstruction for a property that requires low energy radiation such as density. The gaps in the volumetric data may be filled by interpolation of neighboring values, averaging, or by any other suitable method.

<FIG> illustrates an x-ray source target <NUM> and a detector array <NUM> geometry and relationship according to some embodiments. In some embodiments, the x-ray source target <NUM> is activated by a high-energy electron beam <NUM> from an electron source <NUM>. For example, an e-beam <NUM> can be directed to impinge on target <NUM>, which responds by emitting x-rays in 4π directions. Collimators (not shown) may be used to form the emitted radiation into a fan beam, cone beam, pencil beam, or other shaped beam as dictated by application-specific requirements. The shaped beam of radiation enters an examination region <NUM> through which an object passes. A detector array <NUM> may be located diametrically opposite to the radiation emission point and can respond to the attenuated beam of radiation. For example, the detectors along arms 1960a and 1960b of the detector array <NUM> detect x-rays in the fan beam generated along arm 1950a, for example, fan beam <NUM> emitted by x-ray source location <NUM>. In accordance with various embodiments, the plane defined by the detector array can be rotated by an angle <NUM> with respect to the plane defined by the x-ray source target <NUM>. Rotation by an angle <NUM> can help to avoid a situation in which x-rays emitted from the x-ray source target <NUM> are blocked by an arm of the detector array before passing through the examination region <NUM>. For example, radiation emitted at location <NUM> will be blocked on the outer surface of detector arm 1960c if the rotation angle <NUM> is zero. By introducing a non-zero rotation angle <NUM>, radiation is free to pass into the examination region <NUM> before impinging on detector arms 1960a and 1960b as described above. The electron beam <NUM> can be steered to control and sweep the x-ray source target <NUM> including location <NUM>. In example embodiments where the x-ray source target <NUM> includes multiple targetable elements, the scanning electron beam <NUM> can be further configured to irradiate some or all of the targetable elements. In some embodiments, a multitude of targetable elements may be disposed at angles along a trajectory of at least <NUM>° about the direction of transport of an object.

The x-ray source target <NUM> and detector array <NUM> are suitable for use in the imaging system <NUM>. In this embodiment, the beam of electrons <NUM> from the electron source <NUM> is swept across the surface of the x-ray source target <NUM> to cause emission of x-rays over an angular range of less than <NUM>° or at least <NUM>° about the direction of transport of the object <NUM>. Likewise, the speed of transport of an object relative to the scanning speed of the electron beam to cause emission of x-rays from the x-ray source target <NUM> is controlled to provide an imaging modality with a pitch approximately equal to <NUM> or greater than <NUM>.

<FIG> illustrates an example x-ray source and detector geometry according to some embodiments taught herein. In some embodiments, the x-ray source and detector are both fixed in location and do not rotate. As shown in <FIG>, a detector array <NUM> may have multiple segments that form an L-shape or staple shape to cover a greater complement of angles around an object <NUM>. In some exemplary systems, multiple detectors <NUM>, <NUM> can be included within a single system at different locations along the tunnel <NUM> traversed by the object <NUM>. An exemplary system using fixed (i.e., non-rotating or moving) x-ray sources and detectors may include multiple x-ray sources <NUM>, <NUM>, <NUM>, <NUM> that each emit radiation beams toward detectors <NUM>, <NUM>. The x-ray sources <NUM>, <NUM>, <NUM>, <NUM> can be controlled such that only one x-ray source emits toward a given detector at any point in time so that the received measurement data can be properly associated with the correct x-ray source. Multiple x-ray sources <NUM>, <NUM>, <NUM>, <NUM> may be skewed such that the range of angles between a given x-ray source and detector array is not duplicated by another x-ray source and detector combination. It will be apparent to one skilled in the art that any number of x-ray sources and detector arrays could be disposed within an imaging system to achieve any total angular coverage dictated by the specifics of the application. In accordance with various embodiments, the sources <NUM>, <NUM>, <NUM>, <NUM> can be extended targets that emit x-rays when stimulated by a high energy electron beam as described above in relation to <FIG>. In such embodiments, one or more fixed electron beam sources can be configured to irradiate positions along the extended targets. In some embodiments, each extended target can extend through a range of angles of less than <NUM>°, at least <NUM>°, or more than <NUM>° about the direction of transport of an object.

Claim 1:
A method of forming an image of an object, comprising:
receiving, using at least one configurable or programmable processing unit (<NUM>), a three-dimensional array of voxels (<NUM>, <NUM>, <NUM>, <NUM>) representing a physical object (<NUM>), the three-dimensional array of voxels includes data representative of a physical property of the object;
selecting, using the at least one configurable or programmable processing unit, a subset of voxels (230a-230c, 330a-330c, 430a-430c, 530a-530c) from the array of voxels, representing a region of interest, ROI, of the object, the subset of voxels representing one or more portions of a plurality of image slices (202a-202f, 302a-302f, 402a-402f) of the object, the subset of voxels selected along a direction perpendicular to an axis representing a view direction (<NUM>) specific to the ROI; and
forming an image of the ROI by summing mass density values of the object included in the subset of voxels along the view direction, the image representing an estimated total mass of the object in the ROI along the view direction.