Dental tomosynthesis system using patterned exposure sequence

Abstract

An intraoral imaging apparatus has an intraoral detector configured to generate successive images from a series of patterned exposures. An array of x-ray sources is configured to generate the series of patterned exposures to the detector, wherein the sources are distributed over both height and width directions. A controller is configured to generate the series of patterned exposures, wherein the controller is programmed to specify, for each of the plurality of patterned exposures in the series a partial subset of the array sources that are energized to obtain the patterned exposure and exposure energy generated at each array source in the patterned exposure.

Description

DENTAL TOMOSYNTHESIS SYSTEM USING PATTERNED EXPOSURE SEQUENCETECHNICAL FIELD

[0001] The present disclosure relates generally to intraoral imaging and more particularly relates to methods and apparatus for intraoral tomosynthesis imaging.BACKGROUND

[0002] A 3-dimensional (3-D) or volume x-ray image can be of significant value for diagnosis and treatment of teeth and supporting structures. A volume x-ray image for this purpose is formed by combining image data from two or more individual 2-D projection images, obtained within a short time of each other and with a well-defined angular and positional geometry between each projection image and the subject tooth and between each projection image and the other projection images. Cone-Beam Computed Tomography (CBCT) is one established method for obtaining a volume image of dental structures from multiple projection images. In CBCT imaging, an image detector and a radiation source orbit a subject and obtain a series of x-ray projection images at small angular increments. The information obtained is then used to synthesize a volume image that faithfully represents the imaged subject to within the available resolution of the system, so that the volume image that is formed can then be viewed from any number of angles. Commercially available CBCT apparatus for dental applications include the CS 8100 3D System from Carestream Dental LLC, Atlanta, GA.

[0003] While CBCT imaging is a powerful diagnostic tool, however, there can be cases where, even though volume imaging is beneficial, the full-fledged capability of CBCT imaging is not needed. For some functions of volume imaging, such as for use in guiding implant placement, for example, a rudimentary volume imaging capability that provides a measure of depth representation would be suitable. Depth imaging can also help to overcome superposition anomalies between adjacent dental structures. For uses such as these, limited depth information can be sufficient; the use of numerous x-ray projection images, such as those provided from a CBCT system, would not be required. Instead, sufficient volume information can be obtained using a smaller number of x-ray images, provided that a spatial coordinate reference between images is maintained.

[0004] As a general principle, it would be advantageous to obtain the minimum number of x-ray exposures needed in order to generate the volume diagnostic data. A complete CBCT series of projection images, acquired over a 180 degree orbit, requires a correspondingly higher cumulative radiation dosage than does acquisition of a partial series that is either taken over a smaller range of angles or uses fewer projection images taken at increased relative angular increments.

[0005] Tomosynthesis, with provides depth imaging using images acquired over a limited range of angles, appears to offer the dental practitioner a number of advantages over conventional 2D radiography and 3D tomography imaging, such as CBCT imaging, for intraoral features. In tomosynthesis, as with other volume imaging approaches, a limited number of 2D projection images are obtained in sequence, with each image frame shifted in terms of relative angle from the previously acquired image frame. Reconstruction algorithms can then be used to form a volume image of sufficient depth and resolution for a number of diagnosis and assessment functions. This gives tomosynthesis some of the benefits of full-scale tomography imaging for providing volume data, but at lower dose than tomography requires.

[0006] In conventional tomosynthesis imaging, the x-ray source travels along a fixed path that is generally centered on the object being imaged, with the travel path typically curved, as determined by the imaging hardware. Image projections are acquired at discrete positions along the travel path, to acquire image content at incrementally changing source / detector angles. This conventional model has been successful in a number of tomosynthesis applications. However, recent advances in x- ray source arrays and detector technologies make it possible to generate a number of alternative imaging paradigms that are better suited to intraoral imaging tomosynthesisapplications and can help to reduce exposure to the patient without compromising the utility of tomosynthesis results.

[0007] Thus, although a number of solutions have been proposed for providing intraoral tomosynthesis, there remain considerable areas for improvement, as particularly relates to more effective use of improved technologies, along with improvements in reducing patient exposure where multiple images must be acquired.SUMMARY

[0008] An object of the present disclosure is to advance the art of intraoral radiography by providing exemplary apparatus and / or method embodiments for reconstructing a limited-depth image from a small number of x-ray images obtained by an intraoral imaging detector.

[0009] Another object of this disclosure is to address, in whole or in part, at least the foregoing and other deficiencies in the related art.

[0010] It is another object of this disclosure to provide, in whole or in part, at least the advantages described herein.

[0011] These objects are given only by way of illustrative example, and such objects may be exemplary of one or more embodiments of the invention. Other desirable objectives and advantages inherently achieved by the disclosed methods may occur or become apparent to those skilled in the art. The invention is defined by the appended claims.

[0012] According to an aspect of the disclosure, there is provided an intraoral imaging apparatus comprising: an intraoral detector configured to generate successive images from a series of patterned exposures; an array of x-ray sources that is configured to generate the series of patterned exposures to the detector, wherein the sources are distributed over both height and width directions; anda controller that is configured to generate the series of patterned exposures, wherein the controller is programmed to specify, for each of the plurality of patterned exposures in the series:(i) a partial subset of the array sources that are energized to obtain the patterned exposure; and(ii) exposure energy generated at each array source in the patterned exposure.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of the embodiments of the invention, as illustrated in the accompanying drawings.

[0014] The elements of the drawings are not necessarily to scale relative to each other.

[0015] FIG. 1 is a simplified schematic diagram showing a chair side intraoral tomosynthesis imaging apparatus as conventionally configured.

[0016] FIG. 2 is a simplified schematic diagram that shows an intraoral tomosynthesis imaging apparatus according to an embodiment of the present disclosure.

[0017] FIG. 3 is a perspective view showing an exemplary arrangement of x-ray sources on a planar array.

[0018] FIG. 4 is a perspective view showing x-ray coverage from an x-ray source along the edge of the planar array.

[0019] FIG. 5 is a schematic diagram that shows a coverage mapping of the detector for each x-ray source in the planar array.

[0020] FIG. 6 is a schematic view that shows various exemplary exposure patterns for x-ray sources in the array, according to an embodiment of the present disclosure.

[0021] FIG. 7 shows views from tomosynthesis processing using the exposure patterns of FIG. 6.

[0022] FIG. 8A shows a projection image for teeth, obtained using exposure from a central x-ray source in the array.

[0023] FIG. 8B compares an exemplary 2D projection image with a tomosynthesis depth view.

[0024] FIG. 8C compares another exemplary 2D projection image with a tomosynthesis depth view.

[0025] FIG. 9 is a logic flow diagram showing an exposure sequence according to an embodiment of the present disclosure.

[0026] FIG. 10 is a schematic diagram showing multiple sources arranged along a curved surface.

[0027] FIG. 11 is a plan view that shows exemplary coverage when using the arrangement of FIG. 10.

[0028] FIG. 12A is a perspective view that shows a source array arrangement with both thermionic and cold-cathode x-ray emitters.

[0029] FIG. 12B is another perspective view that shows a source array arrangement with both thermionic and cold-cathode x-ray emitters.

[0030] FIG. 12C is a perspective view that shows a source array arrangement along a curved surface, using both thermionic and cold-cathode x-ray emitters.

[0031] FIG. 13 is a perspective view that shows a source array -based tomosynthesis imaging apparatus attached to a treatment chair.

[0032] FIG. 14 shows the use of collimator compensation according to an embodiment of the present disclosure.DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0033] The following is a detailed description of exemplary embodiments, reference being made to the drawings in which the same reference numerals identify the same elements of structure in each of the several figures.

[0034] Where they are used in the context of the present disclosure, the terms “first”, “second”, and so on, do not necessarily denote any ordinal, sequential, or priority relation, but are simply used to more clearly distinguish one step, element, or set of elements from another, unless specified otherwise.

[0035] As used herein, the term “energizable” relates to a device or set of components that perform an indicated function upon receiving power and, optionally, upon receiving an enabling signal.

[0036] In the context of the present disclosure, the terms “viewer”, “operator”, and “user” are considered to be equivalent and refer to the viewing practitioner, technician, or other person who views and manipulates an image, such as a dental image, on a display monitor. An “operator instruction” or “viewer instruction” is obtained from explicit commands entered by the viewer, such as by clicking a button on a camera or by using a computer mouse or by touch screen or keyboard entry.

[0037] In the context of the present disclosure, the phrase “in signal communication” indicates that two or more devices and / or components are capable of communicating with each other via signals that travel over some type of signal path. Signal communication may be wired or wireless. The signals may be communication, power, data, or energy signals. The signal paths may include physical, electrical, magnetic, electromagnetic, optical, wired, and / or wireless connections between the first device and / or component and second device and / or component. The signal paths may also include additional devices and / or components between the first device and / or component and second device and / or component.

[0038] In the present disclosure, the term “detector” refers to the sensing element that is placed in the patient’ s mouth, receives radiation, and provides the image content. Such a detector is a digital detector that provides the image data generated from the x- ray directly to an imaging system, where it is processed and used to form an image for display and recording. For tomosynthesis acquisition, a high-speed digital detector, such as an RVG sensor from Carestream Dental LLC, Atlanta, GA can be used.

[0039] In the context of the present disclosure, the terms “pixel” and “voxel” may be used interchangeably to describe an individual digital image data element, that is, a single value representing a measured image signal intensity, related to a point in space. Conventionally, an individual digital image data element is referred to as a voxel for 3- dimensional volume images and a pixel for 2-dimensional images. Volume images, such as those from CT or CBCT apparatus, are formed by obtaining multiple 2-D images of pixels, taken at different relative angles, then combining the image data, using known algorithmic techniques, to form corresponding 3-D voxels. For the purposes of the description herein, the terms voxel and pixel can generally be considered equivalent, describing an image elemental datum that is capable of having a range of numerical values related to x-ray intensity. Voxels and pixels have the attributes of both spatial location and image data code value.

[0040] The term “set”, as used herein, refers to a non-empty set, as the concept of a collection of elements or members of a set is widely understood in elementary mathematics. The term “subset”, unless otherwise explicitly stated, is used herein to refer to a non-empty proper subset, that is, to a subset of the larger set, having one or more members. For a set S, a subset may comprise the complete set S. A “proper subset” or “partial subset” of set S, however, is strictly contained in set S and excludes at least one member of set S.

[0041] The term “exemplary” indicates that the description is used as an example, rather than implying that it is an ideal.

[0042] Planes can be considered "in parallel" if they are parallel to within no more than 12 degrees in any direction.

[0043] Embodiments of the present disclosure are directed to methods for intraoral imaging, particularly to methods for tomosynthesis imaging that provides a measure of depth imaging suitable for use in analysis and detection of various conditions that can be of diagnostic interest. The present disclosure addresses the need for improved imaging methods that can use 2-D arrays of x-ray sources to provide both conventional2-D radiographic images and the stack of 2-D projection images that are used to form the tomosynthesis image content.

[0044] By way of illustrating the concept of conventional tomosynthesis imaging, the simplified schematic diagram of FIG. 1 shows a tomosynthesis imaging apparatus 20 in which radiation from an x-ray source 14 is directed, at each of several positions over a succession of angles, as represented in dashed lines, toward an intraoral detector 10, retained in the mouth of a patient P. In some imaging apparatus, a single x-ray source 14 is translated over an arcuate path, as shown in FIG. 1, directing radiation to detector 10 at each discrete position over a range of angular increments. Each acquired projection image 12 is recorded as part of the tomosynthesis stack, for further reconstruction processing to generate the tomosynthesis image content. Following the conventional model, a collimator 16 travels with the source 14 to help limit the angle of exposure energy to detector 10. A controller 18 can provide control functions related to translating the position of and energizing x-ray source 14 and acquiring and processing the projection images 12 for rendering on a display 22. Algorithms and processing for tomosynthesis reconstruction are familiar to those skilled in the depthimaging art.

[0045] Considering the basic model outlined in FIG. 1, it can be appreciated that there are a number of variables related to tomosynthesis acquisition, including number of angular positions and thus number of projection images 12 acquired, energy level used by x-ray source 14, and timing required for acquisition of a full sequence that is needed to generate the tomosynthesis image stack. It can be appreciated that better image content is obtained when time delay between captures of projection images 12 is minimized. In addition, it is desirable to reduce exposure to the patient wherever possible, without compromise to image quality.

[0046] To help address the shortcomings of imaging systems that are constrained by following the basic arrangement of FIG. 1, an alternative approach to tomosynthesis acquisition and processing has been developed using an array of x-ray sources (sometimes referred to herein as a “source array”) to direct exposure energy at differentangles for generating the projection image stack. The simplified schematic of FIG. 2 shows a tomosynthesis imaging apparatus 100 with a flat-panel x-ray source array 24 having a plurality of x-ray sources 14 (also, perhaps, referred to as “x-ray emitters 14”), each with a corresponding collimator 16. Using array 24 eliminates the need to transport a single x-ray source 14 along a path, as was shown in FIG. 1 and can provide other advantages for tomosynthesis depth imaging, as described in more detail subsequently. With the source array arrangement shown in FIG. 2, the x-ray sources 14 and detector 10 are not in fixed positions with respect to each other.

[0047] Array 24 can be formed using a configuration of carbon nanotubes (CNT), also termed “cold cathode” sources, or other features. Typically, carbon nanotubes or other nanostructures that can be used for this purpose generate electrons using field emission. Support circuitry then accelerates the electron stream that is directed towards the anode for x-ray generation. For intraoral imaging, each x-ray source 14 can be configured to operate having anode voltage in the 60kV range or slightly higher, for example. With a CNT array, the cathode energy of each source 14 can be individually modulated, thereby varying x-ray emission from the anode. This capability enables the array design to have greater flexibility in terms of imaging depth for tomosynthesis. At the same time, the ability to modulate x-ray energy from one exposure to another adds some complexity to the image reconstruction tasks performed by the system.

[0048] The use of the planar array 24 presents a number of challenges related to efficient use of the emitted x-ray energy. As shown in the perspective view of FIG. 3, in a planar arrangement, each x-ray source 14 emits the bulk of its x-ray energy in the direction perpendicular to the plane (that is, at a normal to the plane). Because of this, the amount of energy received on the detector from any particular source 14 varies according to the position of the particular source 14 within the array, which can be considered with reference to the height and width of the source relative to a normal to the center of detector 10. The FIG. 3 example shows an array 24 of 47 sources 14, arranged in 7x7 fashion. Substantially all of the energy in the cone of emission from a central x-ray source 14c is directed to reach detector 10, with the cone coverage,surrounding a normal N from the central source 14c, extended over the full detector 10 area. As shown in the perspective view of FIG. 4, an x-ray source 14e along the edge of the array 24 provides a cone of radiation which extends only along the periphery of the detector 10 surface. In this way, the actual energy profile for radiation that can be received on detector 10 can vary between neighboring sources 14 on the array 24. The image content obtained from each source 14 on the edges or corners of the array 24 only extends over a portion of detector 10.

[0049] In addition to the capability to provide depth image content due to different incident angles for the x-ray cone, the CNT array 24 also allows independent control of each source 14 in the array. CNT sources can be individually energized, allowing one, two, or more sources 14 to emit x-ray energy, at the same time, toward the subject from their different respective angular positions. Moreover, when using CNT sources 14 in the array, each individual source 14 be adjusted for its energy level, allowing control of the amount of emitted x-ray energy and dose to the subject.

[0050] The schematic view of FIG. 5 shows a coverage map 50, mapping of the coverage area of detector 10 provided by the emission from each of the individual x- ray sources 14 in the array 24. Each of the 49 views in FIG. 5 represents, using a test sample, a “thumbnail” view of detector coverage corresponding to a particular corresponding x-ray source 14 element of the array, indicated as an image 52.

[0051] As noted previously and as is evident from the thumbnail images of FIG. 5, most of the x-ray sources 14 individually provide a radiation cone beam that impinges upon just a partial portion of detector 10. Thus, for example, as noted previously with respect to FIG. 3, sources 14 at or near the center of array 24 emit cones of radiation that substantially encompass the full area of detector 10. X-ray sources 14 that are further from the center source 14c have, correspondingly, less extent of coverage of detector 10 for their emitted energy, as shown, for example, by the enlarged inset Q in FIG. 5.

[0052] As the term is used herein, the center or central x-ray source 14 in the array 24 is the source 14 having the highest percentage of detector 10 within its cone ofradiation. For a planar array 24, the central x-ray source 14 can be considered to be at or closest to the geometric center or midpoint of the array, as shown in FIG. 3, for example. For other array geometries, described subsequently, a similar geometric definition of central source 14, with respect to the array configuration, would apply.

[0053] Referring back to the example of FIG. 4, peripheral x-ray source 14e can provide a cone of emission that partially covers or impinges on detector 10, as shown in an exemplary thumbnail image 52 of inset Q in FIG. 5. In this example, the cone of emission from the corresponding element of array 24 extends over slightly more than 81 % of detector 10. The remaining 19% of the detector 10 surface is not impinged on by emission from source 14c in this example.

[0054] Considered from a different aspect, each pixel in detector 10 can receive light from a partial subset of -ray sources 14. According to an embodiment, each pixel in detector 10 can receive x-ray emission from at least 22 sources 14 and may receive exposure from as many as 28 sources. Table 1 shows, for a typical embodiment, the percentage of detector 10 pixel coverage that is provided using various number of sources; this mapping considers how many sources are visible to each detector pixel. For example, from values in Table 1, it can be seen that only a very few peripheral pixels of detector 10 receive exposure from fewer than 23 x-ray sources 14 from array 24. More than half of the detector pixels receive exposure from 25 or more sources.

[0055] Table 1: Number of sources for detector pixel exposure

[0056] The solution presented herein takes advantage of detector 10 pixel coverage / exposure from multiple sources 14 as described, and the varied angular aspects of x-ray exposure from distributed sources in array 24, to provide patterned exposure energy, provided in a sequence that enables tomosynthesis imaging with reduced patient exposure. Localized intensity, with variable energy released from different sources 14, can also be employed with an array of sources. Different sources 14 can be energized using different kVp / mAs values and extended in energized state for different duration, thus providing different energy levels for the resulting emitted radiation.

[0057] Referring to FIG. 6, there is shown a set of exemplary patterns a) through 1) for exposure provided from array 24. In these examples, exposure can be varied according to source intensity level in a single exposure or, alternately, the number of times each individual source 14 is energized in the sequence. In determining the patterns used and the sequence of exposures provided in order to obtain projection images, one consideration relates to grouping exposures, in order to more efficiently take advantage of otherwise unused detector areas, according to detector coverage, as shown in the example of FIG. 5. Thus, for example, in a single exposure, sources 14 can be grouped accordingly and energized synchronously in order to complement the coverage of the detector 10. A single exposure can simultaneously energize sources ateach of the four comers of the array 24, for example. Subsequent exposures may employ fewer than four sources.

[0058] The same pattern a) - 1) shown in FIG. 6, or other pattern configurations, can be used for each acquired projection image in an exposure series, or patterns can be combined in some way in order to obtain the image information that is needed. It can be appreciated that numerous patterns can be configured using an array having multiple sources; thus, the set shown in FIG. 6 is only exemplary.

[0059] A sequence of exposure patterns can be used, with different sources 14 energized one or more times in the sequence. Thus, for example, in an exposure sequence, a first exposure can be executed by energizing only one or more x-ray sources 14 at or near the center of array 24. A second exposure can follow, utilizing sources 14 between the center and peripheral regions of the array. A third exposure can energize only particular sources 14 that provide angular content of interest for generating the stack of tomosynthesis images. Subsequent images in the series can each apply exposure from different sets of sources 14 in order to generate the needed image content for conventional radiography as well as for tomosynthesis.

[0060] By way of illustration, exemplary exposure times and dose values for the example patterns of FIG. 6 are given in Table 2.

[0061] Table 2. Example Exposure Times and Dose

[0062] According to an embodiment of the present disclosure, data binning or other weighting techniques can be applied in order to compensate for some reduced performance when using peripheral x-ray sources for exposure. Thus, for example, image content that is obtained when using an x-ray source at or near the center or midpoint of the array 24 can be more heavily weighted than image content obtained from x-ray sources at or near edges of the array 24.

[0063] According to an embodiment of the present disclosure, a sequence of images can be obtained by energizing two or more x-ray sources 14 simultaneously, wherein the sources 14 that simultaneously emit are symmetric about a central source 14. Sources 14 can be combined for simultaneously being energized in a single exposure when their respective coverage of the field of view is non-overlapping. Referring to FIG. 5, for example, sources 14 in the comers of the array 24 expose only corresponding comer areas of the detector. These sources 14 are non-overlapping relative to the energy directed to detector 10. By energizing sources 14 in all four comers simultaneously, the detector 10 can be used more efficiently to capture image content for four sources 14 in one exposure and image acquisition. Similarly, array 24 elements can be grouped for simultaneous emission of x-ray energy, based on their relative location about a central source 14c. Using simultaneous source 14 excitation, with selected subsets of sources 14, the number of exposures needed can be significantly reduced.

[0064] An overall goal can be to limit total exposure time of the patient to less than 5 seconds, for example, allowing sufficient time for readout of each acquired projection image, obtaining from 17 to 36 projection images in an exposure session. Exposurewithin these timing constraints could be acquired at rates from 3.4 times per second to higher, depending on the response time of the detector 10.

[0065] The images a) - 1) shown in FIG. 7 show results of tomosynthesis depth imaging, as rendered, using different pattern configurations to display image content for the same depth or layer. Images of dental features at various depths can be rendered using any pattern of array 24 emitters, such as the corresponding patterns a) - 1) for sources given in FIG. 6. Image h) is obtained at high dose, due to relatively long exposure time. Other images in FIG. 7 are taken over a range of dose levels, as determined by the pattern(s) used and exposure duration.

[0066] FIG. 8A shows a projection image obtained from exposure by a central source 14 in array 24 using the timing configuration given for pattern h) above. FIGs. 8B and 8C show side-by-side comparison of an acquired projection image (at left in each figure) with a rendered view (at right) that is available from tomosynthesis processing, optimizing the image content of dental structures at different depths.Exposure Sequence

[0067] The logic flow diagram of FIG. 9 shows steps for execution of an exposure sequence using x-ray source array 24 for a series of exposures, one subset at a time, according to an embodiment of the present disclosure. In an initialization step S910, patient setup and selection of exposure sequence and parameters using array 24 have been completed and the practitioner can begin the exposure sequence, shown as an iterative process to generate projection image 12 content from each individual exposure in the FIG. 9 diagram. Each exposure employs a partial subset of array 24 sources, reducing the overall number of exposures needed. The subset arrangement can be predetermined, based on analysis of x-ray cone emission angles relative to detector 10, for example.

[0068] Continuing with the FIG. 9 sequence, an energization step S920 sets up the subset containing one or more sources 14 to be energized at the same time and for the same duration for the current exposure. An exposure step S93O then exposes detector10 using the energized subset of sources for a predetermined duration and acquires the image content read from detector 10. A preprocessing step S940 provides initial processing to form the 2D projection image formed from energizing the selected subset of sources 14, then stores the 2D projection image for subsequent tomosynthesis image processing. A decision step S950 determines whether or not all of the needed 2D projection images have been obtained and, if not, increments the process to iterate through the next subset. When the tomosynthesis stack of 2D projections is complete, a rendering step S960 can then execute, forming the tomosynthesis content for display of depth images.Non-Planar Exposure Arrays

[0069] According to an alternate example embodiment of the present disclosure, as shown in the FIG. 10 schematic, x-ray source array 24 can have multiple sources 14 arranged along a curved surface, such as along a spherical surface. With each source 14 directed toward sensor 10 as a target, the detector 10 area coverage of each source 14 can be maximized, so that the x-ray cone emitted from each source exposes the full detector 10 area. By way of example, this 100% coverage, available when sources 14 are oriented in the angular manner suggested by the nine sources in FIG. 10, is shown in the nine thumbnail images of FIG. 11.

[0070] According to an alternate embodiment of the present disclosure, positioning components associated with array 24 can be used to adjust or fine-tune the angular orientation of one or more individual x-ray sources 14. One or more actuators 26 can be provided in order to adjust the angular orientation of collimator 16 for the corresponding x-ray source 14 or to shift its spatial position along the array 24 surface. Actuator(s) 26 can be used to adjust the angular position of a single source 14, of multiple sources 14, or of the full array 24.Mixed-Source Exposure Arrays

[0071] According to an embodiment of the present disclosure, the multi-source array 24 can have x-ray sources 14 of different types, including some thermionic sources and some cold-cathode CNT sources. FIG. 12A shows an array 24 arrangement containing CNT multiple x-ray sources 14 and a thermionic source 114. CNT x-ray sources 14 can provide a first level of exposure energy at a first distance from the subject and detector 10. Thermionic source 114 can direct a second level of exposure energy, such as a higher level, from an increased distance. Alternately, thermionic source 114 could be positioned nearer to the subject than are the CNT sources 14.

[0072] FIG. 12B is a perspective view that shows an array 24 configuration wherein thermionic source 114 is disposed along the same surface that supports the CNT sources. In this configuration, it may be useful to have all sources providing the same exposure energy.

[0073] FIG. 12C is a perspective view that shows a configuration in which array 24 is formed on a spherical surface, with thermionic source 114 at a central point in the array 24 and CNT sources 14 distributed about the central source 114.

[0074] It should be appreciated that the patterned exposure and exposure sequences described previously with respect to FIG. 6 can be applied with embodiments using a combination of thermionic sources 114 and spatially distributed CNT sources 14.

[0075] FIG. 13 is a perspective view that shows an array-based tomosynthesis imaging apparatus 200 attached to a treatment chair. Other arrangements, such as wall mount or free-standing arrangements, can be used for array 24. Advantageously, with array configurations, scan mechanisms are not needed. However, additional scan automation can be provided in order to support array operation and extend imaging capabilities. An operator interface can be provided for signal communication with control of imaging apparatus 200, allowing control functions such as practitioner selection of a predetermined exposure sequence as described previously with respect to FIG. 9, for example. Display 22 can also show tomosynthesis imaging results, processed by a processor 118 and selectable for viewing at the site of patient treatmentusing an operator interface 120. This arrangement allows the practitioner to view depth image content, on demand, at the side of the patient.

[0076] According to an embodiment of the present disclosure, actuator 26 can change the angle or position of its corresponding x-ray source 14, such as to reposition the collimator for the x-ray source or to provide a raster scanning pattern. Adjustment can be performed automatically, using control logic in controller 18 (FIG. 2), for example. Actuator 26 can be used to change the position of array 24 during acquisition of a tomosynthesis image sequence.

[0077] Exposure patterns can be generated according to the particular examination type that is needed by the practitioner. User interface tools can be provided to allow the practitioner to set up custom exposure sequence and patterns based on needs of the particular practice. Artificial Intelligence (Al) can be applied in order to generate sets or patterns or modify them for more effective use of the equipment.Image Processing

[0078] Using variable exposure settings generates projection images with different noise levels and variable average means. Calibration procedures that use flat-field (full exposure with any object) and dark current images (no x-ray radiation) can help to provide useful content for image processing and correction.

[0079] The use of multiple x-ray sources 14 in array form can also generate undesirable imagine effects related to collimator features in the reconstructed depth image. Referring to FIG. 14, there is shown how collimator edges can be alleviated or effectively eliminated from a set of projection images. An image 1010 shows collimator edges as they appear in tomosynthesis reconstruction for an array of sources. In practice, these edges could be misinterpreted or could obscure features of interest in the tomosynthesis views. An image 1020 shows an improved image that is generated from projection images conditioned by applying a slight amount of blurring along collimator edges. Although collimator edges are still perceptible, they are less prominent, and less likely to obstruct visibility of features of interest. An image 1030shows further improvement using a more aggressive conditioning of the projection images using blurring. While there can be slight loss of contrast and resolution in the generated tomosynthesis image, collimator edges are very difficult to perceive in image 1030 to which blurring has been applied. Selective blurring of image content is a familiar technique to those skilled in the imaging arts. According to an embodiment of the present disclosure, an operator interface instruction allows the user to adjust the aggressiveness of blurring algorithms for suppressing collimator edge visibility.

[0080] According to an alternate embodiment of the present disclosure, array 24 of x-ray sources can include x-ray emitters of different types. For example, a thermionic x-ray source can be provided as a central x-ray source, with its central ray directed from or extending through middle of the array, with sources arranged along planar or curved surfaces. Surrounding x-ray sources can be formed using nanotube devices, as described previously.

[0081] Embodiments of the present disclosure are thus able to utilize a flat panel array of x-ray sources in order to reduce exposure to the patient when providing tomosynthesis imaging. Imaging anomalies appear to be minimal and can be addressed using various image processing techniques.

[0082] The invention has been described in detail with particular reference to a presently understood exemplary embodiments, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

[0083] The presently disclosed exemplary embodiments are therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.

[0084] A computer program for performing methods of certain exemplary embodiments described herein may be stored in a computer readable storage medium. This medium may comprise, for example; magnetic storage media such as a magnetic disk such as a hard drive or removable device or magnetic tape; optical storage media such as an optical disc, optical tape, or machine-readable optical encoding; solid stateelectronic storage devices such as random access memory (RAM), or read only memory (ROM); or any other physical device or medium employed to store a computer program. Computer programs for performing exemplary methods of described embodiments may also be stored on computer readable storage medium that is connected to the image processor by way of the internet or other network or communication medium. Those skilled in the art will further readily recognize that the equivalent of such a computer program product may also be constructed in hardware.

[0085] It should be noted that the term “memory”, equivalent to “computer- accessible memory” in the context of the application, can refer to any type of temporary or more enduring data storage workspace used for storing and operating upon image data and accessible to a computer system, including a database, for example. The memory could be non-volatile, using, for example, a long-term storage medium such as magnetic or optical storage. Alternately, the memory could be of a more volatile nature, using an electronic circuit, such as random-access memory (RAM) that is used as a temporary buffer or workspace by a microprocessor or other control logic processor device. Display data, for example, is typically stored in a temporary storage buffer that can be directly associated with a display device and is periodically refreshed as needed in order to provide displayed data. This temporary storage buffer can also be considered to be a memory, as the term is used in the application. Memory is also used as the data workspace for executing and storing intermediate and final results of calculations and other processing. Computer-accessible memory can be volatile, nonvolatile, or a hybrid combination of volatile and non-volatile types.

[0086] It should be understood that computer program products for exemplary embodiments herein may make use of various image manipulation algorithms and / or processes that are well known. It should be further understood that exemplary computer program product embodiments herein may embody algorithms and / or processes not specifically shown or described herein that are useful for implementation. Such algorithms and processes may include conventional utilities that are within the ordinary skill of the image processing arts. Additional aspects of such algorithms andsystems, and hardware and / or software for producing and otherwise processing the images or co-operating with the computer program product of the application, are not specifically shown or described herein and may be selected from such algorithms, systems, hardware, components and elements known in the art.

[0087] Exemplary embodiments according to the application can include various features described herein (individually or in combination).

[0088] While the invention has been illustrated with respect to one or more implementations, alterations and / or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the invention can have been disclosed with respect to only one of several implementations / exemplary embodiments, such feature can be combined with one or more other features of the other implementations / exemplary embodiments as can be desired and advantageous for any given or particular function. The term “a” or “at least one of’ is used to mean one or more of the listed items can be selected. The term “about” indicates that the value listed can be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the illustrated exemplary embodiment. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

CLAIMSWhat is claimed is:

1. An intraoral imaging apparatus comprising: an intraoral detector configured to generate successive images from a series of patterned exposures; an array of x-ray sources that is configured to generate the series of patterned exposures to the detector, wherein the sources are distributed over both height and width directions; and a controller that is configured to generate the series of patterned exposures, wherein the controller is programmed to specify, for each of the plurality of patterned exposures in the series:(i) a partial subset of the array sources that are energized to obtain the patterned exposure; and(ii) exposure energy generated at each array source in the patterned exposure.

2. The apparatus of claim 1, wherein the sources in the array are arranged along a planar surface.

3. The apparatus of claim 1, wherein the sources in the array of x-ray sources are arranged along a curved surface.

4. The apparatus of claim 3 wherein, for each x-ray source in the array, an emitted cone of radiation provides exposure energy that extends over the full area of the detector.

5. The apparatus of claim 1 , wherein each x-ray source in the array has a corresponding collimator.

6. The apparatus of claim 1, wherein one or more of the kVp, mAs, and exposure duration are independently controllable for each x-ray source in the array.

7. The apparatus of claim 1, wherein the apparatus further comprises a processor in signal communication with the detector and configured to generate tomosynthesis images.

8. The apparatus of claim 1, wherein the x-ray sources in the array are of both thermionic and cold cathode types.

9. The apparatus of claim 1, wherein the apparatus further comprises at least one actuator that is energizable to provide positional adjustment to a corresponding x-ray source.

10. The apparatus of claim 9, wherein the at least one actuator adjusts the angle of a collimator for the corresponding x-ray source with respect to the detector.

11. The apparatus of claim 1, wherein the apparatus mounts to a patient treatment chair for viewing acquired images following the series of patterned exposures.

12. A tomosynthesis imaging apparatus, comprising: an intraoral detector; a surface comprising multiple X-ray sources, wherein each of the x-ray sources is configured to irradiate at least a portion of the detector;a set of exposure patterns, wherein at least one exposure pattern identifies a subset of the x-ray sources to be energized over the same exposure interval and further identifies exposure settings for each x-ray source in the subset of x-ray sources; and an operator interface for selection of a predetermined sequence of the exposure patterns.

13. A method for acquiring tomosynthesis image content from dental features of a patient, the method comprising the steps of: configuring an intraoral detector to generate successive images from a series of multiple patterned exposures; configuring an array of a plurality of x-ray sources in order to generate the series of patterned exposures to the detector, wherein the x-ray sources are spatially distributed over both height and width directions; generating the series of patterned exposures by energizing one or more elements of the plurality of x-ray sources in a predetermined sequence and acquiring projection image content from the intraoral detector; processing the acquired projection image content to generate the tomosynthesis image; and rendering the generated tomosynthesis image content on a display.

14. The method of claim 13, wherein the method further comprises a step of automatically adjusting the angle of one or more of the plurality of the x-ray sources relative to the detector.

15. The method of claim 13, wherein the method further comprises a step of varying the exposure energy by varying the duration over which one or more of the plurality of x-ray sources is energized.

16. The method of claim 13, wherein configuring the array of x-ray sources further comprises configuring at least one thermionic x-ray source and at least one cold cathode x-ray source.

17. The method of claim 13, wherein the method further comprises a step of scanning one or more of the plurality of the x-ray sources in a raster pattern.

18. The method of claim 13, wherein the predetermined sequence comprises two or more exposures in which different partial subsets of the array of x-ray sources are energized.

19. The method of claim 13, wherein the method further comprises a step of calibrating one or more x-ray sources using both flat-field and dark current images.

20. The method of claim 13, wherein the method further comprises a step of blurring collimator edges in at least one of the acquired projection images.

Images