Patent Description:
A subject, such as a human patient, may undergo a surgical procedure to address an issue in the subject's anatomy. The surgery can include various procedures, such as movement or augmentation of bone, insertion of an implant (i.e. an implantable device), or other appropriate procedures.

Images of a subject can assist a surgeon in planning and performing a procedure. A surgeon may select a two-dimensional image or a three-dimensional image representation of the subject, based on images acquired from an imaging system, such as a magnetic resonance imaging (MRI) system, computed tomography (CT) system, fluoroscopy (e.g. C-Arm imaging systems), or other appropriate imaging systems. The images can assist the surgeon in performing a procedure with less invasive techniques by allowing the surgeon to view the anatomy of the subject without removing the overlying tissue (including dermal and muscular tissue).

From <CIT> an imaging system configured to acquire a selected dose x-ray image projection of a subject according to the preamble of claim <NUM> is known, and from <CIT> a method of acquiring a limited x-ray dose image projection of a subject according to the preamble of claim <NUM> is known.

Further imaging systems configured to acquire a selected dose x-ray image projection of a subject are known from <CIT>, from <CIT>, and from <CIT>.

The object of the disclosure is to provide an improved imaging system configured to acquire a selected dose x-ray image projection of a subject and an improved method of acquiring a limited x-ray dose image projection of a subject.

This object is solved by an imaging system configured to acquire a selected dose x-ray image projection of a subject according to claim <NUM>, and also by a method of acquiring a limited x-ray dose image projection of a subject according to claim <NUM>. Further embodiments are subject of the dependent claims.

Imaging systems may include those disclosed in <CIT>, and entitled "FILTER SYSTEM AND METHOD FOR IMAGING A SUBJECT".

With reference to <FIG>, in an operating theatre or operating room <NUM>, a user, such as a surgeon <NUM>, can perform a procedure on a subject, such as a patient, <NUM>. In performing the procedure, the user <NUM> can use an imaging system <NUM> to acquire image data of the patient <NUM> to allow a selected system to generate or create images to assist in performing a procedure. A model (such as a three-dimensional (3D) image) can be generated using the image data and displayed as an image <NUM> on a display device <NUM>. The display device <NUM> can be part of and/or connected to a processor system <NUM> that includes an input device <NUM>, such as a keyboard, and a processor module <NUM> which can include one or more processors or microprocessors (e.g., central processing units, graphics processor units, etc.) incorporated with the processing system <NUM> along with selected types of non-transitory and/or transitory memory module <NUM>. A connection <NUM> can be provided between the processor <NUM> and the display device <NUM> for data communication to allow driving the display device <NUM> to display or illustrate the image <NUM>.

The imaging system <NUM> can include an O-Arm ® imaging system sold by Medtronic Navigation, Inc. having a place of business in Louisville, CO, USA. The imaging system <NUM>, including the O-Arm ® imaging system, or other appropriate imaging systems may be in use during a selected procedure, such as the imaging system described in <CIT>, <CIT>, and <CIT>.

The imaging system <NUM> may include a mobile cart <NUM>. The imaging system <NUM> may further include a controller and/or control system <NUM>. In various embodiments, the controller <NUM> may be incorporated in the mobile cart <NUM> if present. The control system may include a processor module 33a and a memory module 33b (e.g., a tangible, non-transitory memory). The memory 33b may include various instructions that are executed by the processor 33a to control the imaging system, including various portions of the imaging system <NUM>. The control system may include a processor such as a general purpose processor or a specific application processor and a memory system (e.g., a tangible, non-transitory memory, such as a spinning disk or solid state non-volatile memory). For example, the memory system may include instructions to be executed by the processor to perform functions and determine results, as discussed herein.

The imaging system <NUM> may further include an imaging gantry <NUM> in which is positioned a source unit <NUM> and a detector <NUM>. The gantry <NUM> may be connected to the mobile cart <NUM>. The gantry may be O-shaped or toroid shaped, wherein the gantry is substantially annular and includes walls that form a volume in which the source unit <NUM> and detector <NUM> may move.

The mobile cart <NUM> can be moved from one operating theater to another and the gantry <NUM> can move relative to the cart <NUM>, as discussed further herein. This allows the imaging system <NUM> to be mobile and moveable relative to the subject <NUM>. Thus, the imaging system <NUM> may be used in multiple locations and with multiple procedures without requiring a capital expenditure or space dedicated to a fixed imaging system.

The source unit <NUM> may be an x-ray emitter that can emit x-rays through the patient <NUM> to be detected by the detector <NUM>. As is understood by one skilled in the art, the x-rays emitted by the source <NUM> can be emitted in a cone and detected by the detector <NUM>. The source/detector unit <NUM>/<NUM> is generally diametrically opposed within the gantry <NUM>. The detector <NUM> can move in a <NUM>° motion around the patient <NUM> within the gantry <NUM> with the source <NUM> remaining generally <NUM>° opposed (such as with a fixed inner gantry or moving system) to the detector <NUM>. Also, the gantry <NUM> can move isometrically relative to the subject <NUM>, which can be placed on a patient support or table <NUM>, generally in the direction of arrow <NUM> as illustrated in <FIG>. The gantry <NUM> can also tilt relative to the patient <NUM> illustrated by arrows <NUM>, move longitudinally along the line <NUM> relative to a longitudinal axis <NUM> of the patient <NUM> and the cart <NUM>, can move up and down generally along the line <NUM> relative to the cart <NUM> and transversely to the patient <NUM>, to allow for positioning of the source/detector <NUM>/<NUM> relative to the patient <NUM>. The imaging device <NUM> can be precisely controlled to move the source/detector <NUM>/<NUM> relative to the patient <NUM> to generate precise image data of the patient <NUM>. The imaging device <NUM> can be connected with the processor <NUM> via connection <NUM> which can include a wired or wireless connection or physical media transfer from the imaging system <NUM> to the processor <NUM>. Thus, image data collected with the imaging system <NUM> can be transferred to the processing system <NUM> for navigation, display, reconstruction, etc..

The source <NUM>, as discussed herein, may include one or more sources of x-rays for imaging the subject <NUM>. In various embodiments, the source <NUM> may include a single source that may be powered by more than one power source to generate and/or emit x-rays at different energy characteristics. Further, more than one x-ray source may be the source <NUM> that may be powered to emit x-rays with differing energy characteristics at selected times. Dual energy imaging systems may include those disclosed in <CIT> and <CIT>.

According to various embodiments, the imaging system <NUM> can be used with an un-navigated or navigated procedure. In a navigated procedure, a localizer and/or digitizer, including either or both of an optical localizer <NUM> and an electromagnetic localizer <NUM> can be used to generate a field and/or receive and/or send a signal within a navigation domain relative to the patient <NUM>. The navigated space or navigational domain relative to the patient <NUM> can be registered to the image <NUM>. Correlation, as understood in the art, is to allow registration of a navigation space defined within the navigational domain and an image space defined by the image <NUM>. A patient tracker or dynamic reference frame <NUM> can be connected to the patient <NUM> to allow for a dynamic registration and maintenance of registration of the patient <NUM> to the image <NUM>.

The patient tracking device or dynamic registration device <NUM> and an instrument <NUM> can then be tracked relative to the patient <NUM> to allow for a navigated procedure. The instrument <NUM> can include a tracking device, such as an optical tracking device <NUM> and/or an electromagnetic tracking device <NUM> to allow for tracking of the instrument <NUM> with either or both of the optical localizer <NUM> or the electromagnetic localizer <NUM>. The instrument <NUM> can include a communication line <NUM> with a navigation/probe interface device <NUM> such as the electromagnetic localizer <NUM> with communication line <NUM> and/or the optical localizer <NUM> with communication line <NUM>. Using the communication lines <NUM>, <NUM> respectively, the interface <NUM> can then communicate with the processor <NUM> with a communication line <NUM>. It will be understood that any of the communication lines <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> can be wired, wireless, physical media transmission or movement, or any other appropriate communication. Nevertheless, the appropriate communication systems can be provided with the respective localizers to allow for tracking of the instrument <NUM> relative to the patient <NUM> to allow for illustration of a tracked location of the instrument <NUM> relative to the image <NUM> for performing a procedure.

One skilled in the art will understand that the instrument <NUM> may be any appropriate instrument, such as a ventricular or vascular stent, spinal implant, neurological stent or stimulator, ablation device, or the like. The instrument <NUM> can be an interventional instrument or can include or be an implantable device. Tracking the instrument <NUM> allows for viewing a location (including x,y,z position and orientation) of the instrument <NUM> relative to the patient <NUM> with use of the registered image <NUM> without direct viewing of the instrument <NUM> within the patient <NUM>.

Further, the gantry <NUM> can include an optical tracking device <NUM> or an electromagnetic tracking device <NUM> to be tracked with the respective optical localizer <NUM> or electromagnetic localizer <NUM>. Accordingly, the imaging device <NUM> can be tracked relative to the patient <NUM> as can the instrument <NUM> to allow for initial registration, automatic registration, or continued registration of the patient <NUM> relative to the image <NUM>. Registration and navigated procedures are disclosed in <CIT>. Upon registration and tracking of the instrument <NUM>, an icon <NUM> may be displayed relative to, including superimposed on, the image <NUM>. Briefly, registration includes a transformation of image space and patient space to allow for illustration of a tracked object (e.g. the instrument <NUM>) relative to (e.g. superimposed on) the image <NUM>.

Turning reference to <FIG>, according to various embodiments, the source <NUM> can include a single x-ray tube <NUM> that can be connected to a switch <NUM> that can interconnect a first power source A <NUM> and a second power source B <NUM> with the x-ray tube <NUM>. X-rays can be emitted from the x-ray tube <NUM> in a selected shape or configuration, such as a cone shape, that may be centered about a ray or line <NUM> directed toward the detector <NUM>. The switch <NUM> can switch between the power source A <NUM> and the power source B <NUM> to power the x-ray tube <NUM> at different power parameters, such as selected and different voltages and/or amperages to emit x-rays at different energy characteristics generally in the direction of the vector <NUM> towards the detector <NUM>. The vector <NUM> may be a central vector or ray within the beam of x-rays. The vector <NUM> may include a selected line or axis relevant for further interaction with the beam, such as with a filter member, as discussed further herein.

It will be understood, however, that the switch <NUM> can also be connected to a single variable power source that is able to provide power characteristics at different voltages and/or amperages rather than the switch <NUM> that connects to two different power sources A <NUM> and B <NUM>. Also, the switch <NUM> can be a switch that operates to switch a single power source between different voltages and amperages. Further, the source <NUM> may include more than one source that is configured or operable to emit x-rays at more than one energy characteristic. The switch, or selected system, may operate to power the two or more x-rays tubes to generate x-rays at selected times.

The patient <NUM> can be positioned within the x-ray beam to allow for acquiring image data of the patient <NUM> based upon the emission of x-rays in the direction of vector <NUM> towards the detector <NUM>.

Acquisition of projections with beams (e.g., x-rays beams) at more than one power or energy characteristic (e.g. dual power characteristics) may allow for enhanced and/or dynamic contrast reconstruction of models of the subject <NUM> based upon the image data acquired of the patient <NUM>. It is understood, however, that more than two power sources may be provided or they may be altered during operation to provide x-rays at more than two energy characteristics. In addition and/or alternatively to more than one source and/or power source, a filter assembly <NUM> may be provided to assist in and/or generation of acquisition of projections at multiple power parameters. The discussion herein of two or dual energy is merely exemplary and not intended to limit the scope of the present disclosure, unless specifically so stated.

Further, one or more models may be generated with one or more projections with the imaging system <NUM>. The processor module <NUM>, 33a may execute selected instructions to generate the models. The instructions may include an iterative or algebraic process can be used to reconstruct the model (such as for the image <NUM>) of at least a portion of the patient <NUM> based upon the acquired image data. It is understood that the model may include a three-dimensional (3D) rendering of the imaged portion of the patient <NUM> based on the image data. The rendering may be formed or generated based on selected techniques, such as those discussed herein.

The x-ray tube <NUM> may be used to generate two dimension (2D) x-ray projections of the patient <NUM>, selected portion of the patient <NUM>, or any area, region or volume of interest. The 2D x-ray projections can be reconstructed, as discussed herein, to generate and/or display three-dimensional (3D) volumetric models of the patient <NUM>, selected portion of the patient <NUM>, or any area, region or volume of interest. As discussed herein, the 2D x-ray projections can be image data acquired with the imaging system <NUM>, while the 3D volumetric models can be generated or model image data.

For reconstructing or forming the 3D volumetric image, appropriate algebraic techniques include Expectation maximization (EM), Ordered Subsets EM (OS-EM), Simultaneous Algebraic Reconstruction Technique (SART) and Total Variation Minimization (TVM), as generally understood by those skilled in the art. The application to perform a 3D volumetric reconstruction based on the 2D projections allows for efficient and complete volumetric reconstruction. Generally, an algebraic technique can include an iterative process to perform a reconstruction of the patient <NUM> for display as the image <NUM>. For example, a pure or theoretical image data projection, such as those based on or generated from an atlas or stylized model of a "theoretical" patient, can be iteratively changed until the theoretical projection images match the acquired 2D projection image data of the patient <NUM>. Then, the stylized model can be appropriately altered as the 3D volumetric reconstruction model of the acquired 2D projection image data of the selected patient <NUM> and can be used in a surgical intervention, such as navigation, diagnosis, or planning. The theoretical model can be associated with theoretical image data to construct the theoretical model. In this way, the model or the image data <NUM> can be built based upon image data acquired of the patient <NUM> with the imaging device <NUM>.

The 2D projection image data can be acquired by substantially annular or <NUM>° orientation movement of the source/detector <NUM>/<NUM> around the patient <NUM> due to positioning of the source/detector <NUM>/<NUM> moving around the patient <NUM> in the optimal movement. An optimal movement may be a predetermined movement of the source/detector <NUM>/<NUM> in a circle alone or with movement of the gantry <NUM>, as discussed above. An optimal movement may be one that allows for acquisition of enough image data to reconstruct a select quality of the image <NUM>. This optimal movement may allow for minimizing or attempting to minimize exposure of the patient <NUM> and/or the user <NUM> to x-rays by moving the source/detector <NUM>/<NUM> along a path to acquire a selected amount of image data without more or substantially more x-ray exposure.

Also, due to movements of the gantry <NUM>, the detector need never move in a pure circle, but rather can move in a spiral helix, or other rotary movement about or relative to the patient <NUM>. Also, the path can be substantially non-symmetrical and/or nonlinear based on movements of the imaging system <NUM>, including the gantry <NUM> and the detector <NUM> together. In other words, the path need not be continuous in that the detector <NUM> and the gantry <NUM> can stop, move back the direction from which it just came (e.g. oscillate), etc. in following the optimal path. Thus, the detector <NUM> need never travel a full <NUM>° around the patient <NUM> as the gantry <NUM> may tilt or otherwise move and the detector <NUM> may stop and move back in the direction it has already passed.

In acquiring image data at the detector <NUM>, the selected energy x-rays generally interact with a tissue and/or a contrast agent in the patient <NUM> differently based upon the characteristics of the tissue or the contrast agent in the patient <NUM> and the energies of the two x-rays emitted by the x-ray tube <NUM>. For example, the soft tissue of the patient <NUM> can absorb or scatter x-rays having a first energy differently than the x-rays having a second energy different than the first energy. Similarly, a contrast agent, such as iodine, can absorb or scatter the x-rays at the first energy differently from those at the second energy. Different energy x-rays may be used to distinguish and/or differentiate different types of material properties (e.g. hard or soft anatomy or between two types of soft anatomy (e.g. vessels and surrounding tissue)), contrast agent, implants (e.g. metal implants) and surrounding natural anatomy (e.g. bone), or etc. within the patient <NUM>. By switching between two or more power parameters and knowing the time to generate the x-rays the information detected at the detector <NUM> can be used to identify or segregate the different types of anatomy or contrast agent being imaged.

At least because the x-ray tube <NUM> is in a moveable imaging system, such as the imaging system <NUM>, it can be moved relative to the patient <NUM>. Thus, the x-ray tube <NUM> may move relative to the patient <NUM> while the energy of the x-rays that reach or are attenuated by the subject <NUM> is being changed or altered. Accordingly, an image projection acquired with the first energy may not be at the same pose or position relative to the patient <NUM> as the second energy. If the model is desired or selected to be formed of a single location in the patient <NUM>, however, various interpolation techniques can be used to generate the model. Interpolation may occur between image data acquired at a first time and image data acquired at a second time. The image data at the first and second times may be generated with the two different energies. Thus, the model may be formed including image data from both energies using interpolation between the acquired image data. Further, the interpolation may be to account for an amount of movement (e.g. linear, rotational, etc.) of the x-ray tube <NUM> between when the projection is generated with the first energy and the projection is generated with the second energy. Accordingly, a projection regarding a single pose may be generated with two energies via interpolation that accounts for movement of the source <NUM> during image acquisition.

In addition to and/or alternatively to the generation of x-rays at different energies from one or more sources, the filter assembly <NUM> can be used to assist in insuring or creating a select differentiation between x-ray spectras of x-rays of the two different energies. Filter assemblies that may be appropriate include those disclosed in <CIT> and entitled "FILTER SYSTEM AND METHOD FOR IMAGING A SUBJECT". The filter assembly <NUM> may be operated in a selected manner, such as an interval manner that may be timed and/or gated to relate to various parameters including the image acquisition as discussed above. Therefore, the filter assembly <NUM> can be operated to image the patient <NUM> to achieve the differentiation between the dual energies of the x-rays.

Turning reference to <FIG>, the filter assembly <NUM> is illustrated. The filter assembly <NUM> may include a filter member <NUM> that is carried by a filter carrier <NUM>, wherein the filter carrier <NUM> may rotate around an axis <NUM> on a shaft <NUM>. The filter member <NUM> may be formed of a selected material, including those that selectively attenuate x-rays including lead, aluminum, tin, etc., and fixed to the filter carrier <NUM>. The first filter <NUM> may block or limit selected x-ray photons related to selected energies of a broad spectrum beam, as discussed herein.

The first filter member <NUM> may be fixed or held with the carrier in selected manners such as, bores may be formed in the filter member <NUM> and one or more screws <NUM> fix the filter member <NUM> to the filter carrier <NUM> by passing through or engaging the filter member <NUM> and the filter carrier <NUM>. It is understood that other fixation mechanisms may be provided, such as welding, adhesives, brazing, or the like, to fix the filter member <NUM> to the filter carrier <NUM>. The carrier <NUM> may further be provided as a frame such that x-rays that pass through the filter member <NUM> and reach the detector <NUM> pass through the filter member <NUM>, but not the material of the filter carrier <NUM>.

As illustrated in <FIG>, the filter carrier <NUM> may have a curved outer edge <NUM> such that the filter carrier <NUM> includes a radius <NUM> and has an outer arcuate edge <NUM>. The filter carrier <NUM>, therefore, may form at least a part of a circle or round member. The combination of the filter carrier <NUM> and the filter member <NUM> may have a selected mass that defines or forms only a portion of a circle. Therefore, a counterbalance <NUM> may be fixed to the filter carrier <NUM> to counter balance the mass of the filter member <NUM> and the filter carrier <NUM>.

The counterbalance may have an arcuate outer edge <NUM> and a substantially similar radius <NUM> to the radius <NUM>. The counter balance <NUM>, therefore, may form a circle with the filter carrier <NUM>. The counterbalance <NUM> and the filter carrier <NUM> form a filter carrier assembly <NUM> to move the filter member <NUM> relative to the x-ray to be positioned into or out of the x-rays generally travelling along the direction <NUM>, as schematically illustrated in <FIG>.

In various embodiments, the filter carrier <NUM> may include a second filter member or material <NUM>. The second filter <NUM> may block or limit selected x-ray photons related to selected energies of a broad spectrum beam, as discussed herein. The second filter may be placed in a selected position relative to the first filter <NUM>. The second filter <NUM> may be in place of or positioned as the counterbalance <NUM> to the first filter <NUM>. As the filter carrier <NUM> rotates, therefore, the second filter <NUM> may also be placed in the beam <NUM>.

The filter carrier <NUM> may rotate around the shaft <NUM> that has or forms the central axis <NUM>. The filter carrier <NUM> may be operated to rotate in two directions or in a single direction, such as in the direction of arrow <NUM> around the axis <NUM>. In various embodiments, the filter carrier <NUM> may be moved to carry the filter member <NUM> in substantially one rotational direction.

According to various embodiments, the filter carrier <NUM> may be operated to rotate around the axis <NUM> at a selected rate. The selected rate may be a substantially constant speed and rotation per minute (RPM) and/or changeable for a selected period of time. Therefore, whether the filter member <NUM> is in the beam path <NUM>, the second filter <NUM>, and/or a selected open area (e.g., no filter) may be in the beam path <NUM>. In various embodiments, a selected portion of the filter assembly <NUM> may be placed in the beam <NUM> every about <NUM> milliseconds.

In various embodiments, the filter carrier assembly <NUM> may be connected to a carry gear <NUM>. The carry gear <NUM>, in various embodiments, is driven by a belt <NUM> that is driven by a drive gear <NUM> that is connected to a shaft <NUM> powered by a motor assembly <NUM>. The motor assembly <NUM> may include a housing <NUM> and a powered motor (not specifically illustrated) within the housing <NUM>. The motor assembly <NUM> may be powered by various power mechanisms, such as electrical power, pneumatic power, or the like. The motor assembly <NUM> may be any appropriate motor assembly that can drive the filter carrier assembly <NUM> at the selected speed and be powered by the imaging system <NUM> and controlled by the controller <NUM>. The motor assembly <NUM> may include an appropriate stepper and/or servo motors, for example the Maxon® EC-I-<NUM> brushless DC servo motor sold by Maxon Motor Ag having a place of business in Switzerland.

Control connection <NUM> may be provided and interconnected with the imaging system controller <NUM>. As discussed above, the positioning of the filter member <NUM> may be controlled by the imaging system controller <NUM> to filter x-ray spectra, as discussed above. The filter member carrier assembly <NUM> may be mounted to the carry gear <NUM> through the appropriate mechanism, such as one or more screws, bolts, adhesives, rivets, or other appropriate mechanical or chemical adhesions of the carrier assembly <NUM> to the carry gear <NUM>. Therefore, upon rotation of the drive gear <NUM> the belt <NUM> may drive the carry gear <NUM> to spin the filter carrier assembly <NUM>, including the filter members <NUM>, <NUM>, at a selected rotation rate. It is understood, however, that the motor assembly <NUM> may be directly connected to the carry gear <NUM> without requiring the belt <NUM>. In a direct connection, for example, the carry gear <NUM> may be mounted directly to the shaft <NUM> (e.g. replacing the drive gear <NUM>) and/or the carry gear <NUM> may directly engage the drive gear <NUM> without the belt <NUM> and/or other transmission system. Alternatively, other appropriate drive or transmission mechanisms may be provided between the drive gear <NUM> and the carry gear <NUM> such as a worm drive, a geared transmission, or other appropriate connection systems.

During operation, the position of the filter member <NUM> may be synced with the location of the beam <NUM> in time with the emission of the x-rays at the selected power that are intended or selected to pass through the filter members <NUM>, <NUM> before reaching the patient <NUM>. According to various embodiments, the filter assembly <NUM> may include an encoder assembly. The encoder assembly may be used to sense, determine, and/or transmit a position of the filter carrier <NUM> to the control <NUM> or other appropriate controller. In various embodiments, the encoder may include various components such as a magnetic member <NUM> positioned on the carrier <NUM> and a sensor (e.g. a Hall Effect sensor) <NUM> positioned to sense movement of the magnetic member <NUM>. The encoder may include those disclosed in <CIT> and entitled "FILTER SYSTEM AND METHOD FOR IMAGING A SUBJECT".

With continuing reference to <FIG> and additional reference to <FIG>, the imaging system <NUM> may be used to generate projections of the patient <NUM> with one or a plurality of energies at the detector <NUM>. In particular, energies of a beam, such as an x-ray beam traveling along the path of the ray <NUM>, may impinge or reach the detector <NUM> and/or the patient <NUM> at discrete and selected energies. For example, the beam that travels along the path <NUM> through the patient <NUM> to the detector <NUM> may be selected to be at least at two different energies. The two energies may be separated by a selected amount, as discussed herein.

In various embodiments, for example, the source <NUM> at the x-ray tube <NUM> may transmit or emit a broad spectrum beam, such as an x-ray beam, with many different energy levels which includes a board energy spectrum. For example, the beam emitted by the tube <NUM> may emit a beam 110a in the direction of the ray <NUM> to include a spectrum of energies (e.g., about <NUM> keV to about <NUM> keV), with peak energies of including about <NUM> kVp to about <NUM> kVp, including about <NUM> kVp to about <NUM> kVp. At each of the peak energies, it is understood, however, that a range of energy in a spectra may include the peak value. The beam 110a, however, may be selectively altered and/or filtered.

The beam 110a, as schematically illustrated in <FIG>, is emitted from the tube <NUM>. As the beam passes through the filter assembly <NUM>, it may engage the first filter <NUM> and/or the second filter <NUM>. The beam 110a, therefore, may be attenuated by the two filters <NUM>, <NUM>. In various embodiments, the two filters may limit or attenuate the beam 110a to two different energies in a post-filtered beam portion 110b. Accordingly, the beam 110a may include a pre-filter portion 110a and the second filter portion or post-filter portion 110b. The post-filter portion 110b may have two distinct energies depending upon which filter it is passed through.

As schematically illustrated in <FIG>, the pre-filter beam 110a may be a broad spectrum beams and may have a selected energy range or spectrum, such as that discussed above. The post-filter beam 110b that passes through the first filter <NUM> may have a first beam spectra where low-energy x-ray are attenuated and thus increasing the Half-Value Layer (HVL) which may also alter the kVp of the post-filter beam. With reference to <FIG>, the first filter <NUM> may filter the broad spectrum pre-filter beam portion 110a to a first selected post-filter spectrum 110b' that may also be referred to as a partial or limited beam.

Turning reference to <FIG>, the second filter <NUM> may filter the broad spectrum pre-filter beam 110a to a second selected post-filter beam 110b". The second post-filter beam 110b" may include a selected power characteristic, such as a separate or different spectra or voltage, from the first post-filter beam 110b' and may also have a differing HVL. The second post-filter beam energy 110b", which may also be referred to as a limited or partial beam, may have a second post-filter beam spectra with a higher HVL than the first post-filter beam.

Thus, the first and second post-filter beams may have differing peak energies, such as differing by about <NUM> kVp to about <NUM> kVp, where each beam may be selected from a range of about <NUM> kVp to about <NUM> kVp. Each selected kVp, however, may have a known or understood spread around to the kVp. Further, the HVL may be different between the first and second post-filter beams. For example, the HVL may differ by about <NUM> millimeters of Aluminum (mm Al) to about <NUM> Al, and HVL values for each beam may be selected from about <NUM> Al to about <NUM> Al, including about <NUM> Al to about <NUM> Al. It is understood by one skilled in the art that the HVL is an equivalent thickness of Aluminum (Al) that reduces a beam intensity by one-half.

As illustrated in <FIG>, the filter carrier <NUM> may also define one or more openings or passages 210a. The openings may allow for passage of an unfiltered or broad spectrum beam for image collection and/or other purposes. Thus, image data may be acquired with one or more filter arrangements and/or an open (i.e., broad spectrum beam image data acquisition).

As illustrated in <FIG>, both of the post-filter beams 110b may reach the detector <NUM>. In both instances, however, the post-filter beam 110b may pass through and/or be attenuated by the subject <NUM>. Accordingly, as both of the post-filter beams 110b', 110b" include different energies or power characteristics that are attenuated by the patient <NUM> and reach the detector <NUM> the projectors received or determined with the detector <NUM> may be based upon different beam energies. Therefore, although the single pre-filter beam 110a may be emitted by the source <NUM>, including the x-ray tube <NUM>, the beam attenuated or reaching the subject <NUM> may be differentiated into at least two different beams. The two different energies of the two different post-filter beams 110b', 110b" may be used to differentiate and/or distinguish various features in the patient <NUM> in the image data collected at the detector <NUM> as discussed above. The single source tube and a single pre-filter beam 110a, however, may be used to generate the two post-filter beams with different energies 110b', 110b". The filter assembly <NUM> including the two filter members <NUM>, <NUM> may be used to generate the two different post-filter beams 110b', 110b". It is further understood, however, that the filter assembly may include more than two filters and/or an open area that allow for generation of more than two energies and/or to allow the whole broad spectrum beam to pass in the path <NUM> for image data acquisition.

The image acquisition or image data acquisition of the subject <NUM> at the detector <NUM>, therefore, may proceed in a selected manner, such as according to a method <NUM> as illustrated in <FIG>. The method <NUM> may be used to acquire image projections or image data of the subject <NUM> at two different energies or power characteristics of the beam 110a from the single source tube <NUM> and the single broad spectrum beam 110a. The method may start in block <NUM> which may include positioning the subject <NUM> relative to the imaging system <NUM>, moving the imaging system <NUM> relative to the subject, or other appropriate procedures.

The method <NUM> may be used to collect image data of the subject <NUM> with either the first post-filter beam 110b' or the post-second filter beam 110b". It is understood, however, that additional filters may be provided and, therefore, additional or more than two post-filter beams with different and distinguishable energies may also be produced. Further, although the method herein illustrates and refers to the use of the two filters <NUM>, <NUM>, it is understood that only a single filter may be used to collect all projections of the subject <NUM> and/or only two filters may be selected out of a plurality of filters, for operation of the imaging system <NUM>. Accordingly, the discussion herein of using the two filters <NUM>, <NUM> is merely exemplary for including a plurality of filters to achieve a plurality of post-filtered beam energy for collection of a plurality of image data of the subject <NUM>.

Accordingly, the method <NUM> after the start in block <NUM> may include selecting a position for the first energy image projection in block <NUM>. For example, the image assembly <NUM> can include rotation of the source <NUM> relative to the subject <NUM> and/or other movements of the gantry <NUM> relative to the subject <NUM>. As discussed above, the gantry <NUM> may move axially along a long axis <NUM> of the subject <NUM> in the direction of arrow <NUM>, rotate in the direction of arrow <NUM>, move perpendicular to the long axis <NUM>, and/or orthogonal to the axis <NUM> in the direction of arrow <NUM>. Accordingly, the selection of a position for the first energy projection in block <NUM> may include positioning the source <NUM> relative to the subject <NUM> in any appropriate position. For example, it may be desired to acquire image data for imaging and/or reconstructing a model of a selected portion of the subject, such as a selected vertebrae. One skilled will understand, therefore, positioning the imaging system for acquiring the first energy projection may include positioning the imaging system <NUM> relative to the subject <NUM> for acquiring a selected image.

After making the selection in block <NUM>, the first filter may be moved into the broad spectrum beam in block <NUM>. As discussed above the first filter <NUM> may be moved into the beam path <NUM> to produce the first filter beam 110b'. Thus the collection of image data with the first filter beam may proceed in block <NUM>. After collecting the first image data with the first filter beam in block <NUM> a selection of a position for a second energy image projection may be made in block <NUM>. As discussed above, the second energy image need not be collected, however, if collecting a second energy is selected a determination of a position may be made in block <NUM>. The position may be a selected position made in a manner similar to that discussed above regarding the selection for the first energy projection in block <NUM>. In various embodiments, for example, it may be selected to include a projection at the subject <NUM> that both of the energy, and, therefore, movement of the imaging system, such as the source <NUM> including the x-ray tube <NUM>, may not occur. It is understood, however, that the source <NUM> may move such as rotating around the subject <NUM> and/or due to movement of the gantry <NUM> relative to the subject.

After selecting a position for the second energy projection in block <NUM> the second filter <NUM> may be moved into the beam 110a in block <NUM>. After moving the filter into the beam 110a, the second filter beam 110b" may pass the filter assembly <NUM> for collection of image data as a second filter beam in block <NUM> may occur. Accordingly, image data may be collected at both of the energies with the post-filter beams 110b', 110b" by movement of the respective filters <NUM>, <NUM> into the beam 110a. The single broad spectrum beam 110a may be filtered to generate or create either and/or both of the post-filter beams 110b', 110b". The post-filter beams 110b may also be referred to as partial or limited spectrum beams as they are limited or partial spectrums of the broad spectrum beam 110a.

After collection of the second filter beam image data in block <NUM>, a determination of whether additional projections are needed may be made in block <NUM>. If no additional projections are needed or selected, a NO path <NUM> may be followed to an end block <NUM>. Ending in block <NUM> may include ending or collection projections with either of the filtered beams 110b', 110b". However, it is understood that additional processes may occur, such as reconstruction of a selected model, performing of a procedure on the subject <NUM>, or other appropriate post-imaging processes may occur.

If addition projections are selected in block <NUM>, a YES path <NUM> may be followed. The YES path <NUM> may allow for a selection of acquiring either or both of image projection with the first or second filtered beam. As discussed above, the filter assembly <NUM> may also include open or blanks areas 210a in the filter carrier. Thus, the full or broad spectrum beam 110a may also be used to collect image data, if selected. It is understood, therefore, that a broad spectrum image may also be collected at block <NUM>. It is understood, however, that a broad spectrum image is optional.

After determination and/or collection of the optional broad spectrum image collection, a first filter beam path <NUM> may be followed to select a position of the first energy image projection in block <NUM> to continue or loop the process. Accordingly, either only the first energy image projection may be collected and/or both the first and second energy projection may be collected.

In addition and/or alternatively thereto, however, a second filtered beam path <NUM> may also be followed. The second filtered beam path <NUM> may move to selecting a position for the second energy image projection in block <NUM>. Again, as discussed above, image data may be collected at either or both of the first or second energy and/or other additional energies, and/or need not be collected at all of the selected energies. Thus, the YES path <NUM> may include collecting images at any selected energy and/or broad spectrum energies, as illustrated above.

The imaging system <NUM> including the single x-ray beam source <NUM> may emit a broad spectrum beam 110a. Selected filters, such as the first and second filters <NUM>, <NUM> may filter the single broad spectrum beam 110a to two filtered or partial spectrum beams 110b', 110b". The two filtered beams 110b', 110b" may include energies that allow for collection of two different energy image projections for selected purposes, such as for distinguishing selected contrast agents, selected tissues, or other appropriate matter with distinguishable attenuation characteristics. Nevertheless, the imaging system <NUM> may include the filter assembly <NUM> to allow for generation of the two energy beams even if the x-ray source tube <NUM> of the source <NUM> only emits only a single broad spectrum initial or primary beam.

As discussed above, the imaging system <NUM> may be used to acquire image data of the subject <NUM> for reconstruction of a model thereof. Reconstructing a model of the subject <NUM> may include using a plurality of projections acquired with the imaging system <NUM> to generate a 3D model of the subject <NUM>. Image data, therefore, acquired relative to the subject <NUM> at a plurality of positions and/or over a period of time may be used to reconstruct the model, such as the model <NUM> for display on the display device <NUM>. The reconstruction may occur as discussed above. In various embodiments, however, a reconstruction of the model <NUM> for display may be based upon various types of image data acquired of the subject <NUM>. As discussed above, dual energy image data may be acquired of the subject <NUM>. In addition to and/or alternatively to, a low dose or lower dose image acquisition technique may be used to acquire image data of the subject <NUM> for performing the 3D reconstruction. In various embodiments, for example, the source <NUM> may be positioned at various positions relative to the subject <NUM> and acquisition of image projections may be made at the different positions that are used for the reconstruction. The reconstruction, therefore, is based upon the plurality of projections. In various embodiments, each of the projections may be at a single or selected dose, such as with a different spectra of energy. Thus, the x-ray does to the subject <NUM> may be limited, as opposed to acquire all image data with the broad spectrum, by about <NUM>% to about <NUM>%.

The acquisition of image data of the subject for performing a reconstruction to generate a three-dimensional image may, for example, include acquiring projection at selected intervals around the subject <NUM>. With reference to <FIG>, the imaging system <NUM> is schematically illustrated. The imaging system <NUM> may include the source <NUM>' that is moved within and/or relative to the gantry <NUM>. It is understood that the detector <NUM> may also move relative to the source <NUM> for acquisition of image projections of the subject <NUM>. Accordingly, while the <FIG> schematically illustrates the gantry <NUM> and the source <NUM>', it is understood that the detector and other portions of the imaging system <NUM> may also be present. Nevertheless, the source <NUM>' may move around a circle, or other appropriate shape relative to the subject <NUM>, with the imaging system <NUM>. As illustrated in <FIG>, for example, the source <NUM>' may move to various selected positions, any number of positions may be selected and the eight illustrated positions are only exemplarily. It is understood, however, that the source <NUM>' may move to any appropriate number of positions to acquire projections of the subject <NUM> to ensure adequate data collection for performing the image reconstructions.

In various embodiments, for example, the imaging system <NUM> may be operated, such as by the controller <NUM> based upon input by the user <NUM>, or other appropriate input, to move the source <NUM> relative to the subject <NUM> in the exemplary eight positions (or other appropriate positions) illustrated in <FIG>. At each of the positions the source <NUM> may emit high power or a selected power of x-rays that are detected at a detector for acquisition of image projections of the subject <NUM>. The image projections may allow for reconstruction of a selected image, such as a three-dimensional model, of the subject <NUM>.

In various embodiments, however, the eight positions of the source <NUM> may be used to acquire projections of the subject <NUM> at different or varying intensities of the x-rays beam. In various embodiments, the filter assembly <NUM> may be used in the source <NUM> to alter a power of the beam emitted by the x-ray tube <NUM> through the subject <NUM>. In various embodiments, for example, with reference to <FIG>, the source assembly <NUM>' may include a filter assembly <NUM>', similar to the filter assembly <NUM> as discussed above. The filter assembly <NUM>' may include the first filter <NUM> and an open or unfiltered portion <NUM>. The open portion <NUM> may be an opening or void in the filter carrier <NUM>. As discussed above the x-ray tube or tube <NUM> may emit a pre-filter beam 110a. The pre-filter beam may be filtered by the first filter <NUM> to be a filter beam 110b. The first filter <NUM> may filter the pre-filter beam 110a to be a low energy post filter beam 110b.

Turning reference to <FIG>, the filter assembly <NUM>' may rotate or move the filter carrier <NUM> such that the filter <NUM> is moved out of the beam <NUM> and the void <NUM> is moved into the beam 110a. The source assembly <NUM>'a, therefore, may include the void <NUM> positioned within the beam 110a. In this position or configuration, therefore, the source assembly <NUM>'a may be used to emit a full power beam such that the beam after passing the filter carrier <NUM> is the same power and unfiltered. Thus, the full beam power that is emitted by the tube <NUM> may pass through the subject or interact with the subject <NUM> and be detected at the detector <NUM>.

Returning reference to <FIG> and with continuing reference to <FIG>, the imaging system <NUM> may acquire image projections of the subject <NUM> at different powers or different attenuations at different positions relative to the subject <NUM>. For example, as illustrated at <FIG>, the source assembly <NUM> may be configured as the source assembly <NUM>' such that the filter <NUM> is positioned in the beam 110a to filter or reduce a power of the beam as it passes through the subject <NUM> or it interacts with the subject <NUM>. At the positions of the source <NUM>'a, the source assembly <NUM>'a may include an unfiltered beam, thus being configured to allow an unfiltered beam to pass from the source tube <NUM> and interact with the subject <NUM>. As illustrated in <FIG>, the source assembly <NUM> may be configured to alternatively change or alternate between the high power and low power beam that reaches the subject <NUM>. As illustrated in <FIG>, the imaging system <NUM> may ease the single source tube <NUM> to alter a power of the x-rays reaching the subject <NUM>.

The imaging system <NUM> with the source assembly <NUM> may be configured into at least two configurations, including the configuration <NUM>', as illustrated in <FIG>, and the configuration <NUM>'a, as illustrated in <FIG>. The x-ray tube <NUM> may emit the beam 110a. In the first or filtered configuration the first filter <NUM> may filter the beam 110a such that the source assembly <NUM> emits the filtered beam 110b. The filtered beam 110b may be a low power beam and/ or different spectra that reaches the subject <NUM>. The low power beam 110b may include selected power characteristics such as kVp and amount of beam filtration.

The source assembly <NUM>'a configuration may include an unfiltered region <NUM> of the filter carrier <NUM> and/or filter assembly <NUM> such that the emitted beam 110a emits or leaves the source assembly <NUM>'a and reaches the subject <NUM> at a full or first power. Thus, the source assembly <NUM>'a may allow for an emission of a high power radio beam to reach the subject <NUM>.

As illustrated above, therefore, the single source assembly <NUM> including the single source tube <NUM> may be used to emit a beam at a high power or first power 110a and a second or low power 110b. As illustrated in <FIG> the source assembly <NUM> may be changed between configurations in alternating positions or to acquire alternating frames of image projections of the subject <NUM>. Thus, the imaging system <NUM> may be used to acquire image projections of the subject <NUM> at two different powers at different positions.

The low power beam 110b may allow for acquisition of image projections of the subject <NUM> at a lower power than the higher full power beam 110a. Thus, when alternating the configuration of the source assembly <NUM>, as illustrated in <FIG>, a selected set of image projections may be acquired of the subject <NUM> at a lower dose than if all of the projections were acquired at the higher full dose. As exemplary illustrated in <FIG>, a full set of projections may be acquired of the subject <NUM> at a selected reduction of power. Thus, the x-ray does to the subject <NUM> may be limited, as opposed to acquire all image data with the broad spectrum, by about <NUM>% to about <NUM>%.

The total selected projections acquired for a reconstruction, therefore, may be done at a total lower dose (e.g. of x-rays) to the subject <NUM> due to the low power acquisitions at <NUM>' at the positions as illustrated in <FIG>. The high dose projections <NUM>'a allow for a high signal to noise ratio for reconstructing a model of the subject <NUM>. The low power projections may have a lower signal to noise ratio, but provide appropriate data for assisting in the reconstruction of the model <NUM> of the subject <NUM>. For example, the low power projections may allow for an identification of edges of various features, such as bony or high attenuation structures, of the subject <NUM>. Accordingly, while a high signal to noise ratio may not be achieved with a low powered projection, selected information may be acquired for assisting in a reconstruction. Interpolation may be made between the high and low powered projections to assist in the reconstruction. The reconstruction, therefore, may use the low power projections, even though a lower signal to noise ratio may be achieved, to perform the reconstruction.

Various reconstruction techniques may be used to construct the model <NUM> of the subject <NUM>, even with the lower signal to noise ratio image projections. The lower signal to noise ratio projections may also be referred to as noisy projections, even though they include selected data.

Various reconstruction techniques may include, to perform a reconstruction, for example, a machine learning system. The machine learning system may be trained to identify features in the high noise projections to assist in defining the reconstruction using the sparse data collection technique including the selected or alternating high energy or high dose projections. The low dose projections may allow for or generate a sparse image acquisition or data acquisition of the subject <NUM>, with a selected reconstruction techniques may be used to textualize the sparse data, such as identifying edges within the low dose projections. The high does projections may be used to identify spatial resolution and to perform the reconstruction and a low loss reconstruction may be provided with the high noise projections used to interpolate or assist in the reconstruction method. Thus, the x-ray does to the subject <NUM> may be limited, as opposed to acquire all image data with the broad spectrum, by about <NUM>% to about <NUM>%.

In various embodiment, the imaging system <NUM> including the filter assembly <NUM>, as discussed above, may include additional or alternative filter members such as those included in a filter system <NUM> as illustrated in <FIG>. The filter system <NUM> may include a filter carrier <NUM>', similar to the filter carrier <NUM>, as discussed above. The filter carrier <NUM>' may be driven by various assemblies and portions, including those as discussed above, such as the motor or motor assembly <NUM> that may be driven directly and/or via various belts as discussed above. Nevertheless, the filter carrier <NUM> may rotate relative to the source <NUM> and the detector <NUM>. The source <NUM> may emit a beam along the beam path <NUM>. The beam emitted by the source <NUM> may pass through a portion of the filter carrier <NUM> and reach and/or be blocked or filtered by the filter portion on the filter carrier <NUM>.

In various embodiments, the filter carrier may carry or move one or more filter portions. The filter carrier <NUM> may hold a first filter portion <NUM>, a second filter portion <NUM>, a third filter portion <NUM>, and a fourth filter portion <NUM>. Each of the filter portions may be similar to one another, but include varying sections, as discussed further herein, that may block a portion or region of the beam <NUM>. In various embodiments, for example, each of the filter portions <NUM>, <NUM>, <NUM>, <NUM> may be provided to assist in detecting and/or correcting for scattering of the beam <NUM> between the source <NUM> and the detector <NUM>. The beam <NUM> may be an x-ray beam that is emitted by a tube, such as the tube <NUM>, and the source <NUM>. The x-ray beam may pass through or relative to the filter carrier <NUM> to the detector <NUM> and be detected for generating an image projection of the subject, such as the subject <NUM>. The beam 110a, however, may be scattered by various interactions, including air or other material interactions.

Each of the filter sections <NUM>-<NUM>, may include different or selected configurations. For example, the filter section in <NUM> may include a filter or blocking portion <NUM> and an opening or blank portion <NUM>. The blocking section <NUM> may include a portion that substantially or entirely blocks the beam 110a from passing through the filter section <NUM> toward the detector <NUM>. The blocking section <NUM> may, for example, include a high density x-ray blocking material such as lead, or other appropriate materials. The void <NUM> may be substantially open, such as an air void or opening positioned relative to the blocking portion <NUM>. The filtering section <NUM> may include a selected dimension, such as a first dimension <NUM> and a second dimension <NUM>. The dimensions <NUM>, <NUM> may generally be known or consistent for each section or portion that a projection may be acquired of the subject <NUM> at the detector <NUM>. Accordingly, the filter carrier <NUM>' may also be formed of a substantially blocking material such that the beam 110a passes substantially only through the filter portions, including the void <NUM> of the filter portion <NUM>.

The filter carrier <NUM>, as discussed above, may include a selected number, such as four of the filter regions including the filter region <NUM>, the filter region <NUM>, the filter region <NUM>, and the filter region <NUM>. Each of the filter regions may include substantially blocking portions, such as the blocking portions <NUM>, <NUM>, and <NUM> of the respective filter regions <NUM>, <NUM>, <NUM>. Each of the filter regions may also include respective void or opening portions <NUM>, <NUM>, and <NUM> of the respective filter regions <NUM>, <NUM>, <NUM>. Accordingly, each of the filter regions may include substantially blocking regions <NUM>, <NUM>, <NUM>, and <NUM> and respective open or void regions <NUM>, <NUM>, <NUM>, and <NUM>.

Each of the filter regions <NUM>, <NUM>, <NUM>, <NUM> may be positioned relative to the beam <NUM>. As illustrated in <FIG>, the respective void and blocking portions that are positioned within the beam <NUM> may allow for defining or passing the beam through different blocking portions relative to void portions to identify or block selected halves, allowing for defining quadrants of the detector <NUM>. As illustrated in <FIG>, as the filter carrier <NUM> rotates around a center point <NUM> in a selected direction, such as generally in the direction of <NUM>, each of the filter regions <NUM>, <NUM>, <NUM>, <NUM> pass through the beam <NUM>. Each of the filter regions including the blocking portions allow for blocking one-half of the detector space or surface. As each of the four blocking regions or filter regions pass through the beam <NUM>, therefore, quadrants may be defined on the detector <NUM>. The blocking regions positioned relative to the opening or void regions allow for imaging or defining scattering portions of the beam <NUM>.

With continuing reference to <FIG> and additional reference to <FIG>, the filter region <NUM> is illustrated, as an example. The filter region <NUM>, as discussed above, includes the void portion <NUM> and the blocking portion <NUM>. The source <NUM> may emit the beam <NUM> past the filter region <NUM> and toward the detector <NUM>. As illustrated in <FIG>, the blocking region <NUM> blocks a portion of the beam <NUM> such as substantially about one-half of the beam <NUM>, including the blocked beam portion 110x. The open or blade portion <NUM> allows for the beam <NUM> to pass and allows for a passing or unblocked beam portion 110y.

As illustrated in <FIG>, the beam <NUM> may be split or at least partially partitioned between the blocked portion 110x and the passing or through portion 110y. The passing portion 110y, and also referred to as a partial beam, may contact the detector <NUM> to generate or allow for a projection to be produced of the passing portion 110y. The blocked portion 110x, however, is generally blocked from reaching the detector <NUM>. As illustrated in <FIG>, the filter region <NUM>, including the through or void portion <NUM> and the blocking filter <NUM>, allows for the separation of the beam <NUM> into the blocked portion 110x and the passing portion 110y. As discussed above, the filter carrier <NUM> may include a selected number of portions, such as the four filter void regions or portions <NUM>, <NUM>, <NUM>, <NUM> to allow for generation or selection of different blocked portions of the beam <NUM> and the blocking portion or filter portion <NUM> as illustrated in <FIG> is merely exemplary.

The filter region <NUM>, including the other filter regions as discussed above, including the blocking portion <NUM> generally blocks at least a portion of the detector <NUM> from the beam <NUM>. The beam <NUM>, however, may have an amount of scattering due to various interactions of portions of the beam <NUM>, portions interacted or reached by the beam <NUM> or other factors. In various embodiments or under various condition, therefore, the beam <NUM> may have scattering such that all of the rays, such as x-rays in the beam <NUM>, do not travel on a straight path from the source <NUM> to the detector <NUM>. The scattering may be detected and/or determined as discussed herein.

As illustrated in <FIG>, for example, the beam or portions of the beam passing through the void region <NUM> may be scattered due to various interaction from a path directly or straight from the source <NUM> to the detector <NUM>. The portion of the beam <NUM> that passes substantially straight from the source <NUM> to the detector <NUM> may generally pass along or in the region of the unblocked beam 110y. Portions of the beam that pass through the void region <NUM> may be scattered for various reasons. As illustrated in <FIG>, therefore, exemplary scattered portions of the beam may include scattered portions 110za, zb, zc. The scattered portion(s) 110za, zb, zc may contact the detector <NUM> in a generally blocked region or area 38x, which may also be referred to as an occluded portion or region. The blocked region 38x may generally be a region of the detector <NUM> that is blocked due to the blocking region <NUM> of the filter region or portion <NUM>. Accordingly, any detection in the blocked region <NUM> would generally be due to scattering 110za, zb, zc of the beam <NUM>. The scattered beam portion 110za, zb, zc may interact or reach the detector <NUM> in the blocked region 38x. It is understood that different positions of the blocking portion, such as the blocking portion <NUM> including the blocking portions <NUM>, <NUM>, and <NUM>, as discussed above, may produce or allow for a determination of different scattering regions or portions.

With continuing reference to <FIG>, and reference to <FIG>, scattered beam information (i.e. the detected portions on the detector <NUM> in the blocked region 38x) may be used to selectively determine and/or correct for scattering distortion and/or artifacts in image data. With reference to <FIG> an image data or projection <NUM> is illustrated. The imaged projection <NUM> may include an unblocked or beam projection portion 110y'. A blocked or non-image projection portion 110z' may also be included in the image data <NUM>. As schematically illustrated in <FIG>, the imaged projection <NUM> may include the unblocked region 110y' that include substantially an eradiation of the entire region of the detector <NUM> with the beam <NUM>. As discussed above, the void region <NUM> may allow for a passage of the beam <NUM> to the detector <NUM> in the area 110y.

The projection at <NUM>, however, will generally include a void or un-projected region due to the blocking of the detector <NUM> by the blocking region <NUM>. Scattering, however, as discussed above, may allow for a scattering of portions of the beam 110za, zb, zc. Scattered portions of the beam 110y may produce selected detections on the detector <NUM> that may be detected for projection or image data <NUM>. As exemplary illustrated in <FIG>, the blocked portion may include scattered projection data 110za', 110zb', and 110zc'. It is understood that any appropriate or scattered amount of data may be detected at the detector <NUM> in the blocked region. Accordingly, the projection <NUM> may include more than the three scattered points, as illustrated in <FIG>, which are included nearly for the example discussion herein.

The projection <NUM>, acquired with a selected one of the filter regions, as discussed above, may be used for correction of image data collected with the imaging system <NUM>. As discussed above, the various projection or blocking regions may be used to determine any appropriate division of the detector <NUM> for scattering image data or artifacts. The exemplary inclusion of the four projection regions or filter regions is merely exemplary. Nevertheless, each of the filter regions may allow for a determination of a selected amount of scattering relative to the detector <NUM> and the source <NUM>.

The projection image <NUM>, as exemplary illustrated in <FIG>, can include the scattering image data. The scattered image data 110z' may be used for correction of image data collected with the imaging system. For example, any filter applied to the imaging system <NUM>, even including a lower or partial filtering filter may allow for or include scatter image data. Accordingly, the scattering filter, including the scattering filter regions <NUM>-<NUM> as discussed above, may allow for collection of scattering projections, including that illustrated in <FIG> as the scattering image <NUM>. Scattering images may be collected with the imaging system <NUM>. The scattering images may then be used to subtract from the selected projection to allow for correction of scatter data and image projections. For example, as illustrated in <FIG>, the scattered projection points 110za', 110zb', and 110zc' may be subtracted from selected image projections acquired with the imaging system <NUM>. The scatter data may be subtracted to allow for reducing artifacts due to scattering when collecting image projections of the subject <NUM> with the imaging system <NUM>. Also, the occluded portion 38x that may allow the acquisition of the image region 110z' may vary over time. That is, during the image data acquisition (i.e., projection acquisition) the filter may move over time to occlude a different portion of the detector <NUM>. Thus, the occluded region or portion may vary or change with each acquisition, and each acquisition may change over time due to movement of the imaging system <NUM> and/or the filter portion <NUM>. Thus, the position of the occluded portion created by the filter member <NUM> may be time varying with and relative to an acquisition time.

Accordingly, the imaging system <NUM> may include one or more filter portions that allow for filtering and selection of selected image projections collected with the imaging system <NUM>. The filter portions may generate scattering image data or projections due to interactions of x-ray beams from the source <NUM> due to physical properties thereof and/or the environment through which the projection or beam passes. The scattering filters, such as the filter portions <NUM>-<NUM> may be moved into the beam <NUM> to assist and/or determine scattering of the beam <NUM> in the imaging system <NUM>. The scattering filter or regions <NUM>-<NUM>, therefore, may assist in determining or correcting for scattering as discussed above.

It is not intended to be exhaustive or to limit the invention. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.

Claim 1:
An imaging system (<NUM>) configured to acquire a selected dose x-ray image projection of a subject (<NUM>), comprising:
a source (<NUM>) configured to emit x-rays as a whole beam with a first energy spectra;
a filter assembly (<NUM>), including:
a filter member (<NUM>) configured to limit a transmission x-rays to a filtered beam with a second energy spectra that has a different HVL than the first energy spectra,
a filter carrier (<NUM>) configured to move the filter member (<NUM>) relative to the whole beam;
a detector (<NUM>) configured to detect the whole beam and the filtered beam;
a control system (<NUM>) configured to control the position of the filter member (<NUM>) with the filter carrier (<NUM>) to selectively acquire projections of the subject (<NUM>);
wherein the control system (<NUM>) is configured to execute instructions to control movement of the filter carrier (<NUM>) to position the filter member (<NUM>) in filtering position and a non-filtering position;
wherein the filter member (<NUM>) limits the whole beam to the filtered beam in the filtering position;
wherein the imaging system is configured to acquire a selected number of projection to reconstruct a model of the subject (<NUM>),
wherein the imaging system (<NUM>) further comprises:
a reconstruction system configured to reconstruct the model of the subject (<NUM>) with image data acquired with the whole beam and the filtered beam for a reduced x-ray dose image acquisition;
wherein the filtered beam includes a lower dose of x-rays relative to the whole beam,
characterized in that
the filtered beam is operable with the detector (<NUM>) to identify edges of selected portion of the subject (<NUM>).