Patent Publication Number: US-2007100234-A1

Title: Methods and systems for tracking instruments in fluoroscopy

Description:
BACKGROUND OF THE INVENTION  
      This invention relates generally to computed tomography (CT) imaging and more particularly, to tracking instruments during interventional CT Fluoroscopy.  
      In at least one known CT system configuration, an x-ray source projects a fan-shaped beam which is collimated to lie within an X-Y plane of a Cartesian coordinate system and generally referred to as the “imaging plane” The x-ray beam passes through the object being imaged, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is dependent upon the attenuation of the x-ray beam by the object. Each detector element of the array produces a separate electrical signal that is a measurement of the beam attenuation at the detector location. The attenuation measurements from all the detectors are acquired separately to produce a transmission profile.  
      In known third generation CT systems, the x-ray source and the detector array are rotated with a gantry within the imaging plane and around the object to be imaged so that the angle at which the x-ray beam intersects the object constantly changes. A group of x-ray attenuation measurements, i.e., projection data, from the detector array at one gantry angle is referred to as a “view” A “scan” of the object comprises a set of views made at different gantry angles, or view angles, during one revolution of the x-ray source and detector. In an axial scan, the projection data is processed to construct an image that corresponds to a two dimensional slice taken through the object. One method for reconstructing an image from a set of projection data is referred to in the art as the filtered back projection technique. This process converts the attenuation measurements from a scan into integers called “CT numbers” or “Hounsfield units,” which are used to control the brightness of a corresponding pixel on a display device.  
      To reduce the total scan time, a “helical” scan may be performed. To perform a “helical” scan, the patient is moved while the data for the prescribed number of slices is acquired. Such a system generates a single helix from a one fan beam helical scan. The helix mapped out by the fan beam yields projection data from which images in each prescribed slice may be reconstructed.  
      Reconstruction algorithms for helical scanning typically use helical weighting (“HW”) algorithms which weight the collected data as a function of view angle and detector channel index. Specifically, prior to filtered back projection, the data is weighted according to a helical weighting factor, which is a function of both the view angle and detector angle. As with underscan weighting, in a HW algorithm, projection data is filtered, weighted, and backprojected to generate each image.  
      In multi-slice CT fluoroscopy, a fan beam of x-rays is projected toward a detector that includes a plurality of rows of detector elements in the z-axis direction. Each row of detector elements is used to reconstruct an image of a target lying between the source of the x-ray beam and the detector. Any number of images may be combined to generate a volumetric image of the target and/or sequential frames of images to help, for example, in guiding a needle to a desired location within a patient. A frame, like a view, corresponds to a two dimensional slice taken through the imaged object. Particularly, projection data is processed at a frame rate to construct an image frame of the object.  
      In CT Fluoro systems, it is generally advantageous to increase the frame rate while minimizing image degradation. Increasing the frame rate provides advantages including, for example, that an operator physician is provided with more timely (or more up to date) information regarding the location of, for example, a biopsy needle. However, increasing the frame rate generally adversely affects minimizing image degradation. For example, an increase in the frequency that projection data is filtered, weighted and backprojected, tends to slow the frame rate. The frame rate is thus limited to the computational capabilities of the CT Fluoro system. As the number of acquired slices per gantry rotation offered in multi-slice CT systems increases, the user is unable to use all the information available. More specifically, in interventional CT procedures the user is challenged when attempting to monitor multi-slice scanners which are capable of presenting multiple images at frame rates often exceeding approximately  10  frames per second. With multi-slice CT Fluoro systems, one to three thick-slice summations of the available thinner axial slices can be presented as summed images, however, such a summation foregoes the potential resolution enhancement afforded by thin slice imaging. As a result, such summation may not provide the possible improved needle placement accuracy afforded by multi-slice scanners.  
      Additionally, the trajectory of the needle insertion during the interventional procedure (biopsy, drainage etc.) may be different from the axial plane such that in conventional CT single-slice interventional procedures, the needle insertion is generally limited to the image plane only and any Z direction needle position change requires patient table movement in the appropriate direction. The decision regarding the correct magnitude and direction of this movement requires experience and frequently involves a “trial and error” approach. Moreover, there is an added risk of moving the patient table and patient In and Out of the gantry aperture during the procedure while the needle remains inserted in the patient&#39;s body.  
     BRIEF DESCRIPTION OF THE INVENTION  
      In one embodiment, an imaging system for displaying an instrument in a region of interest is provided. The imaging system includes a multi-slice detector, a processor coupled to the multi-slice detector, and a display configured to display reconstructed images. The processor is configured to receive a plurality of multi-slice scan data, identify at least a portion of an instrument in at least one slice of the plurality of multi-slice scan data, and display the identified instrument portion with an indicator associated with the at least one slice.  
      In another embodiment, a computer system is provided. The computer system is configured to receive a plurality of multi-slice scan data, and identify at least a portion of a needle-like instrument positioned in at least one slice of the multi-slice scan data with an indicator associated with the slice.  
      In yet another embodiment, a method of displaying an instrument in a region of interest is provided. The method includes associating an indicator including at least one of a color, a shading, and a pattern with each slice of a multi-slice image of a region of interest, identifying at least a portion of an instrument in at least one slice, and applying the indicator associated with the slice, to the identified instrument portion in that slice.  
      In still another embodiment, an imaging scanner is provided. The imaging scanner includes a data acquisition apparatus configured to acquire imaging data from a subject, a monitor configured to display images reconstructed from the acquired imaging data and a computer programmed to acquire multiple slices of imaging data from the subject having an intracorporeal device positioned therein, reconstruct a multi-slice image from the multiple slices of imaging data, and cause the monitor to display the multi-slice image at a real-time frame rate while preserving information of a position of the intracorporeal device contained in the multiple slices of imaging data for observation by a human observer.  
      In another embodiment, a method of tracking an invasive instrument relative to a target using an imaging system that includes a movable patient table and a multi-slice detector array to automatically move the scan plane of the imaging system within the Z coverage area of the multi-slice detector array is provided. The method includes determining an intracorporeal trajectory of the instrument, displaying a tip of the instrument in at least one of a plurality of adjacent slices, and translating a patient table when the tip reaches a substantial extent of the Z coverage area. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a pictorial view of a multi-slice volumetric CT imaging system;  
       FIG. 2  is a block schematic diagram of the multi-slice volumetric CT imaging system illustrated in  FIG. 1 ;  
       FIG. 3  is a flow chart of an exemplary method of displaying an instrument in a region of interest;  
       FIG. 4  is an exemplary CT fluoroscopy scan image that includes a region of interest;  
       FIG. 5  is another exemplary CT fluoroscopy scan image that includes the region of interest shown in  FIG. 4 ;  
       FIG. 6  is an exemplary display that may be output through the display shown in  FIG. 2 ;  
       FIG. 7  is a side schematic view of an embodiment of the patient table that may be used with the imaging system shown in  FIG. 1 ;  
       FIG. 8  is a flow diagram of an exemplary method of a tracking algorithm to automatically move the scan plane within the Z coverage of the multi-slice detector array; and  
       FIG. 9  is a exemplary CT fluoroscopy scan image area that includes a region of interest described in method in  FIG. 8 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.  
      Also as used herein, the phrase, “reconstructing an image” is not intended to exclude embodiments of the present invention in which data representing an image is generated but a viewable image is not. Therefore, as used herein the term, “Image,” broadly refers to both viewable images and data representing a viewable image. However, many embodiments generate (or are configured to generate) at least one viewable image. Additionally, although described in detail in a CT medical setting, it is contemplated that the benefits accrue to all imaging modalities including, for example, ultrasound, Magnetic Resonance Imaging, (MRI), Electron Beam CT (EBCT), Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT), and in both medical settings and non-medical settings such as an industrial setting or a transportation setting, such as, for example, but not limited to, a baggage scanning CT system for an airport or other transportation center.  
       FIG. 1  is a pictorial view of a CT imaging system  10 .  FIG. 2  is a block schematic diagram of system  10  illustrated in  FIG. 1 . In the exemplary embodiment, a computed tomography (CT) imaging system  10  is shown as including a gantry  12  representative of a “third generation” CT imaging system. Gantry  12  has a radiation source  14  that projects a cone beam  16  of X-rays toward a detector array  18  on the opposite side of gantry  12 .  
      Detector array  18  is formed by a plurality of detector rows (not shown) including a plurality of detector elements  20  which together sense the projected X-ray beams that pass through an object, such as a medical patient  22 . Each detector element  20  produces an electrical signal that represents the intensity of an impinging radiation beam and hence the attenuation of the beam as it passes through object or patient  22 . An imaging system  10  having a multi-slice detector  18  is capable of providing a plurality of images representative of a volume of object  22 . Each image of the plurality of images corresponds to a separate “slice” of the volume. The “thickness” or aperture of the slice is dependent upon the thickness of the detector rows.  
      During a scan to acquire radiation projection data, gantry  12 , and the components mounted thereon rotate about a center of rotation  24 .  FIG. 2  shows only a single row of detector elements  20  (i.e., a detector row). However, multi-slice detector array  18  includes a plurality of parallel detector rows of detector elements  20  such that projection data corresponding to a plurality of quasi-parallel or parallel slices can be acquired simultaneously during a scan.  
      Rotation of gantry  12  and the operation of radiation source  14  are governed by a control mechanism  26  of CT system  10 . Control mechanism  26  includes a radiation controller  28  that provides power and timing signals to radiation source  14  and a gantry motor controller  30  that controls the rotational speed and position of gantry  12 . A data acquisition system (DAS)  32  in control mechanism  26  samples analog data from detector elements  20  and converts the data to digital signals for subsequent processing. An image reconstructor  34  receives sampled and digitized radiation data from DAS  32  and performs high-speed image reconstruction. The reconstructed image is applied as an input to a computer  36  which stores the image in a mass storage device  38 .  
      Computer  36  also receives commands and scanning parameters from an operator via console  40  that has a keyboard. An associated display  42 , for example, a monitor, allows the operator to observe the reconstructed image and other data from computer  36 . The operator supplied commands and parameters are used by computer  36  to provide control signals and information to DAS  32 , radiation controller  28  and gantry motor controller  30 . In addition, computer  36  operates a table motor controller  44  which controls a motorized table  46  to position patient  22  in gantry  12 . Particularly, table  46  moves portions of patient  22  through gantry opening  48 .  
      In one embodiment, computer  36  includes a device  50 , for example, a floppy disk drive or CD-ROM drive, for reading instructions and/or data from a computer-readable medium  52 , such as a floppy disk or CD-ROM. In another embodiment, computer  36  executes instructions stored in firmware (not shown). Generally, a processor in at least one of DAS  32 , reconstructor  34 , and computer  36  shown in  FIG. 2  is programmed to execute the processes described below. Of course, the method is not limited to practice in CT system  10  and can be utilized in connection with many other types and variations of imaging systems. In one embodiment, computer  36  is programmed to perform functions described herein, accordingly, as used herein, the term computer is not limited to just those integrated circuits referred to in the art as computers, but broadly refers to computers, processors, microcontrollers, microcomputers, programmable logic controllers, application specific integrated circuits, and other programmable circuits.  
       FIG. 3  is a flow chart of an exemplary method  300  of displaying an intracorporeal device, such as a medical instrument in a region of interest. The method includes acquiring  302  a plurality of multi-slice scan data. Each slice of the multi-slice scan is analyzed and the portion of the instrument included in each slice is identified. Identification is performed automatically by any of a number of techniques, for example, but not limited to, an image threshold detection based on the relatively high CT values of the instrument, for example, a metallic needle, and/or techniques such as image analysis or preprocessed sinogram data analysis based on pre-designated entrance and target locations. Using such analyses a position of the instrument is determined  304  within the region of interest with respect to each slice of the multi-slice scan data.  
      In the exemplary embodiment, each thin slice of an n-slice multi-slice scanner is designated a specific indicator, such as a color, a shade, a pattern, or a texture that is chosen such that a natural continuum of n colors corresponds to the n detector rows. The selected continuum could be, for example, a heat spectrum, a rainbow, or other progression of colors. Similarly, a continuum of shading, patterns or textures may be associated with each detector row. Associating elements of the continuum is performed on a slice by slice basis, where segments or portions of the instrument that appear in the slice are assigned the appropriate element for the selected continuum. In one embodiment, for example, a rainbow spectrum is selected as the continuum for a color indicator for a biopsy needle instrument. In a rainbow spectrum the colors transition from red, orange, yellow, green, blue, indigo and violet. The colors are not discrete bands of color, rather the colors transition continually from violet to red. In the case where six slices are used to reconstruct the image of the region of interest, each slice is assigned a color based on the selected continuum. In the example of the rainbow spectrum, a first slice at one end of the region of interest is assigned red, an adjacent slice is assigned the color orange, the next adjacent slice is assigned the color yellow, and so on to the other end of the region of interest. A portion of the biopsy needle that is located in each slice is colorized the same color as the color assigned to the slice. Accordingly, a color, shade, pattern, or texture is associated  306  with each portion of the instrument and the slice in which the portion was positioned.  
      In the exemplary embodiment, an image of the region of interest is reconstructed using a plurality of the image slices from the multi-slice scan data. An image of the instrument, colorized in colors associated with each slice where the portion of the instrument was located is reconstructed. A combined image of multiple slices of the region of interest and the portions of the instrument associated with the slices is then displayed  308 .  
       FIG. 4  is an exemplary CT fluoroscopy scan image area  400  that includes a region of interest  402 . A medical instrument, such as a biopsy needle  404  is positioned within region of interest  402  during a procedure. A plurality of image slices of a cross section of region of interest  402  includes a portion of needle  404 . In the exemplary embodiment, a slice  406  at a first end of region of interest  402  includes a base portion  408  of needle  404 , a slice  410 , and a slice  412  include portions of needle  404  that pass through each slice, and a slice  416  near the center of region of interest  402  includes a tip portion  418  of needle  404 . Slices  420 ,  422 , and  424  do not include any portion of needle  404 . In the exemplary embodiment, each slice is associated with a different color of a selectable color spectrum continuum  426 . For example, slice  406  is associated with red, slice  410  with red-orange, slice  412  with orange, slice  416  with yellow, slice  420  with light green, slice  422  with green, and slice  424  with blue. In various embodiments of the present invention, other selected spectrums and/or indicators will yield different colors, shading, pattern, or texture associated with each of slices  406 ,  410 ,  412 ,  416 ,  420 ,  422 , and  424 .  
      An image  428 , reconstructed from the scan data associated with slice  406  includes an image portion  430  of needle  404 . Portion  430  is colorized red, the color associated with the slice in which it is positioned. An image  432 , reconstructed from the scan data associated with slice  410  includes an image portion  434  of needle  404 . Portion  434  is colorized red-orange, the color associated with the slice in which it is positioned. Images  436  through  444  are likewise reconstructed from the scan data associated with scan data for slices of region of interest  402 . Each of images  436  through  444  only includes a portion of needle  404  that is positioned within that slice. For example, image  436  includes an image portion  437  of needle  404  and image  438  includes an image portion  439  that illustrates tip  418  of needle  404 . If needle  404  is not positioned such that any portion of needle  404  is located within a slice, the image corresponding to that slice will not include a portion of needle  404  in the image. For example, images  440 ,  442 ,  444  do not include a corresponding portion illustrating a position of needle  404  because needle  404  is not positioned such that a portion of needle  404  is located within the slice corresponding to images  440 ,  442 ,  444 .  
       FIG. 5  is another exemplary CT fluoroscopy scan image area  500  that includes region of interest  402  shown in  FIG. 4 . Biopsy needle  404  is positioned within region of interest  402  during a procedure. In the exemplary embodiment, needle  404  is positioned such that tip  418  is located within slice  416  as shown in  FIG. 4 , except that needle  404  enters region of interest  402  from a different location than that shown in  FIG. 4 . A plurality of image slices of a cross section of region of interest  402  include a portion of needle  404 . In the exemplary embodiment, slice  424 , at a second end of region of interest  402 , includes base portion  408  of needle  404 , slice  422  and slice  420  include portions of needle  404  that pass through each slice, and slice  416 , near the center of region of interest  402 , includes tip portion  418  of needle  404 . Slices  412 ,  410 , and  406  do not include any portion of needle  404 . In the exemplary embodiment, each slice is associated with a different color of a selectable color spectrum continuum  426  as illustrated above with regard to  FIG. 4 . Slice  406  is associated with red, slice  410  with red-orange, slice  412  with orange, slice  416  with yellow, slice  420  with light green, slice  422  with green, and slice  424  with blue.  
      Image  444 , reconstructed from the scan data associated with slice  424  includes an image portion  502  of needle  404 . Portion  502  is colorized blue, the color associated with the slice in which it is positioned. Image  442 , reconstructed from the scan data associated with slice  422  includes an image portion  504  of needle  404 . Portion  504  is colorized green, the color associated with the slice in which it is positioned. Images  428  through  440  are likewise reconstructed from the scan data associated with scan data for slices of region of interest  402 . Each of images  428  through  440  only includes a portion of needle  404  that is positioned within that slice. For example, image  440  includes an image portion  506  of needle  404  and image  438  includes image portion  508  that illustrates tip  418  of needle  404 . If needle  404  is not positioned such that any portion needle  404  is located within a slice, the image corresponding to that slice will not include a portion of needle  404  in the image. Accordingly, images  436 ,  432 , and  428  do not include a corresponding portion illustrating a position of needle  404  because needle  404  is not positioned within the slice corresponding to images  436 ,  432 , and  428 .  
       FIG. 6  is an exemplary display  600  that may be output through display  42  (shown in  FIG. 2 ). A multi-slice relatively thicker image  602  includes an image comprising a plurality of slices. A composite view  604  of needle  404  is displayed as needle segments along with their proper color coding that are combined into a single multi-color needle shaft (if it passes through adjacent slices) whose orientation can be instantly understood. For example, as illustrated in  FIG. 4 , if red-orange-yellow-green-blue is assigned to the cranial-caudal slices, then a needle tip that is blue indicates a needle trajectory towards the feet, while a red tip indicates needle  404  is positioned towards the head. A yellow needle tip designates that it is positioned substantially in the middle of region of interest  402 .  
      The viewer is presented a first viewing area  606  including single composite thick slice image  602  that is comprised of a combination, such as a summation, of the acquired n thin slices and overlayed with the multi-color composite needle segments. In the exemplary embodiment, this single composite slice is updated at high frame rates for observer viewing.  
      Improved placement information may be obtained by displaying a second viewing area  608  that includes a thin-slice image, for example, image  438  showing the needle tip, alongside combined thick slice image  602 . Second viewing area  608  provides the viewer with a detailed, thin-slice, high-resolution image for confirmation of needle tip positioning. Automatic needle-tip identification and tracking may be accomplished in a similar fashion to the techniques described above.  
      In another embodiment, a third viewing area (not shown) displays a second thin-slice image, selected to lie in the plane of the target anatomy. This allows the observer to further confirm that needle  404  has reached the target.  
      A legend  610  indicates relative positions of the slices associated with each color, texture, or pattern used in composite thick slice image  602 . Another legend  612 , displayed with the thin slice image selected in second viewing area  608  illustrates the relative position of the portion of needle  404  associated with the slice selected and displays the needle portion in the color, texture, or pattern associated with that slice to facilitate confirmation of the position of needle  404  in any portion of region of interest  402 .  
       FIG. 7  is a side schematic view of an embodiment of patient table  46  that may be used with imaging system  10  (shown in  FIG. 1 ). In the exemplary embodiment, patient  22  is lying on patient table  46  that includes a positioning motor  702  communicatively coupled to table motor controller  44  that automatically positions table  46  such that needle-tip  418  and region of interest  402  always lie in or near the central slice of system  10 . Identification of needle tip  418  is performed automatically by any of a number of techniques, for example, but not limited to, an image threshold detection based on the relatively high CT values of the needle, and/or techniques such as image analysis or preprocessed sinogram data analysis based on pre-designated entrance and target locations. When needle tip  418  is identified, a command is sent to table motion controller  44  to reposition table  46  such that needle tip  418  is aligned with a central portion of display  42 . Such needle-tracking is particularly appropriate where the needle insertion is significantly skewed to the axial plane, accordingly, such a method potentially permits needle insertion while maintaining the user&#39;s hands substantially outside of the x-ray beam.  
       FIG. 8  is a flow diagram of an exemplary method  800  of a tracking algorithm to automatically move the scan plane within the Z coverage of the multi-slice detector array rather than moving the patient table to follow the needle tip.  FIG. 9  is an exemplary CT fluoroscopy scan image area  900  that includes a region of interest described in method  800  in  FIG. 8 . The acquired data is analyzed using the attenuation information from one or more reconstructed images, raw data and/or preprocessed data to substantially determine the exact needle position. The reconstructed image displaying the needle tip will slide automatically according to the needle tip movement and the upper beam collimator will automatically track the needle tip movement in the Z direction, in order to reduce the patient and the operator dose. In the exemplary embodiment, the region of interest is represented by sixteen images, such as detector rows  901 - 916 , each image corresponding to a slice of a sixteen slice detector.  
      Based on a previously performed volume scan, the user locates  802  a display cursor on each of a needle tip entry point and a target. These two points may be located at different table positions (images) to determine the planned needle trajectory.  
      The system moves  804  the patient table such that the needle tip appears on an image, for example, an image  918  using a calculation based on the display cursor locations. In the exemplary embodiment, the initial entry direction (3D angle) of the needle is adjusted by the user using a guide (i.e. laser, calipers, lights, etc.). In an alternative embodiment, tuning of the initial entry angle is based on acquiring continuous or “tap” scanning with very low dose of the needle out of the patient just prior to insertion into the patient. The calculation is based on at least two images wherein the images are based on data acquired by more than one detector row.  
      The XY angle of the needle is continuously verified  806  based on the information from image  920 . The angle relative to the Z-axis is continuously verified based on the information from image  918  and image  920 .  
      The needle movement direction is calculated  808  on image  918  by continuously subtracting the actual (current) and previous images  918 . If the needle movement is slow, and the frame rate is fast, then the subtraction is performed on images  918  with longer time gaps.  
      Based on the initial entry direction (3D angle), calculated needle movement direction and slice thickness, the expected needle tip appearance area  924  on image  922  is predicted  810 . If the needle is completely included in only one image, each adjacent image, for example, image  920  and image  922  are both monitored  812  in their predicted areas. These areas will be located adjacent to the needle tip position on image  918 .  
      The area corresponding to the predicted appearance point on an image  922  is continuously verified  814  by subtracting the actual (current) image  922  from reference images  922  acquired previously. Verification that the needle tip has reached image  922  is confirmed by observing a dramatic density change within the predicted appearance area and/or confirmation of the density change for several consecutive reconstructed images. In the specific case where the needle is rigid, straight and has a relatively small angle (relative to z axis), the two adjacent images  920  and  922  may be sufficient for monitoring the needle positioning and predicted areas  918 . For curved interventional tools the calculation can be done using thinner slice thicknesses and enlarging the predicted appearance areas  918 .  
      After the confirmation, the system generates  816  images from rows  907 ,  908 ,  909 , and  910  instead of rows  906 ,  907 ,  908 , and  909  and the needle tip will remain in the displayed image  907  as before and the upper beam collimator translates  818  in the Z-direction a corresponding amount and direction.  
      The system verifies  820 , in real-time, on-line, that the needle is traveling along the predetermined trajectory. If the needle deviates substantially from the predetermined trajectory by exceeding a selectable position threshold, a warning is indicated to the user. Such a warning is advantageous for procedures where the needle trajectory and the target area are not in the same imaged plane.  
      When the needle tip reaches  822  a limit of the Z coverage of the multi-slice detector array, for example, by exiting the last slice of the array, the user is warned that movement of the patient table, either manually or automatically, is necessary to maintain the needle tip within the viewing capability of the system.  
      Because the needle is able cross more than one slice plane (i.e. the needle is skewed to the scanner&#39;s axial plane), a significant dose saving to the user may be achieved by, for example, tilting the gantry. The system is programmed to determine  824  a recommended optimum gantry tilt angle for the specific interventional procedure used.  
      The above-described embodiments of an imaging system provide a cost-effective and reliable means for displaying wide scan coverage imaging while maintaining thin-slice detailed imaging for medical instrument insertion accuracy. More specifically, the needle color-coding provides a single thick-slice image while still showing thin-slice needle positioning to facilitate simultaneously benefiting from both aspects of multi-slice CT. As a result, the described embodiments of the present invention facilitate imaging a patient in a cost-effective and reliable manner.  
      Exemplary embodiments of imaging system methods and apparatus are described above in detail. The imaging system components illustrated are not limited to the specific embodiments described herein, but rather, components of each imaging system may be utilized independently and separately from other components described herein. For example, the imaging system components described above may also be used in combination with different imaging systems. A technical effect of the various embodiments of the systems and methods described herein include at least one of facilitating imaging a patient with images wherein instrument placement accuracy is enhanced.  
      While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.