Apparatus and methods for performing scalable multislice computed tomography scan

Information

  • Patent Grant
  • 6275562
  • Patent Number
    6,275,562
  • Date Filed
    Tuesday, November 17, 1998
    26 years ago
  • Date Issued
    Tuesday, August 14, 2001
    23 years ago
Abstract
A scalable multislice system which, in one embodiment, includes a scalable multi-slice detector, a scalable data acquisition system (SDAS), scalable scan management, control, and image reconstruction processes, and scalable image display and analysis, is described. In the axial multi-slice scan mode, multiple rows of scan data can be processed before image reconstruction, and the data can be used to produce either multiple thin slices or a reduced number of thicker slices with reduced image artifact. In addition, images with thicker slice thicknesses can be later reconstructed retrospectively into thinner slices of images based on clinical diagnosis needs. As a result, the number of unwanted images for viewing, filming, and archiving is reduced. In addition, high z-axis resolution images can be later reconstructed for patient diagnosis. In the helical multi-slice scan mode, multiple combinations of patient table speed and x-ray beam and detector collimations, enable generation of images having different z-axis resolution can be produced. For example, at the table speed of 30 mm/rotation, images of 5-10 mm slices can be generated. Thicker slice (such as 10 mm) images can be generated prospectively, which provides the benefit of a reduced number of images and reduced image reconstruction time. At a later time, thinner slice images can be generated retrospectively using the same data. Such thinner slice images may be necessary depending on the clinical application needs. Such thinner slice images can be generated without rescanning the patient.
Description




BACKGROUND OF THE INVENTION




This invention relates generally to computed tomograph (CT) imaging and, more particularly, to a multi-slice CT scanner having a scalable x-ray collimator, x-ray detector, x-ray data acquisition system, scan data processing, and scan image reconstruction.




Typical CT patient scans are executed in either an axial mode (i.e., patient table stops, scan executed, and then patient table moves to next location) or in a helical mode (i.e., patient table moves continuously during the scan). Single slice scanners are common, and dual (two) slice CT systems are known. At least some of the commercially available dual slice systems have a number of limitations. Tradeoffs between patient scan speed, image quality, and x-ray tube loading generally must be made in performing such scans. For example, in order to obtain improved image quality, the patient scan speed may have to reduced or the x-ray tube loading must be increased, or both. Increasing patient scan speed may result in degraded image quality or require increased x-ray tube loading, or both. Until now, no known system provides the benefits of increased patient scan speed, improved image quality, and reduced x-ray tube loading.




Further, the known commercially available dual slice systems are not scalable in that such dual slice systems cannot be configured to collect more than two slices of data. Until now, no know system enables an operator to select for axial scans, the slice thickness and number of images per rotation, and for helical scans, the slice thickness, scan mode, and scan speed.




BRIEF SUMMARY OF THE INVENTION




These and other objects may be attained by a scalable multislice system which, in one embodiment, includes a scalable multi-slice detector, a scalable data acquisition system (SDAS), scalable scan management, control, and image reconstruction processes, and scalable image display and analysis. As used herein, the term scalable generally means that an operator can readily and simply select the desired number of slices and the slice thickness for images to be displayed. In the present multislice system, multiple rows of x-ray scan data can be acquired. In addition, increased patient scan speed, improved image quality, and reduced x-ray tube loading are achieved.




In the axial multi-slice scan mode, multiple rows of scan data can be processed before image reconstruction, and the data can be used to produce either multiple thin slices or a reduced number of thicker slices with reduced image artifact. In addition, images with thicker slice thicknesses can be later reconstructed retrospectively into thinner slices of images based on clinical diagnosis needs. As a result, the number of unwanted images for viewing, filming, and archiving is reduced. In addition, high z-axis resolution images can be later reconstructed for patient diagnosis.




In the helical multi-slice scan mode, multiple combinations of patient table speed and x-ray beam and detector collimations, enable generation of images having different z-axis resolution can be produced. For example, at the table speed of 30 mm/rotation, images of 5-10 mm slices can be generated. Thicker slice (such as 10 mm) images can be generated prospectively, which provides the benefit of a reduced number of images and reduced image reconstruction time. At a later time, thinner slice images can be generated retrospectively using the same data. Such thinner slice images may be necessary depending on the clinical application needs. Such thinner slice images can be generated without rescanning the patient.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a pictorial view of a CT imaging system.





FIG. 2

is a block schematic diagram of the system illustrated in FIG.


1


.





FIG. 3

is an exemplary embodiment of a scan user interface than can be used in conjunction with the system illustrated in

FIGS. 1 and 2

.





FIG. 4

is a perspective view of a CT system detector array.





FIG. 5

is a perspective view of a detector module shown in FIG.


4


.





FIG. 6

illustrates the geometric configuration of the CT system illustrated in FIG.


1


.





FIG. 7

is a schematic illustration of x-ray generation and detector components view from a side of the gantry.





FIGS. 8

,


9


and


10


illustrate operation of the cam collimator in the CT system illustrated in FIG.


1


.





FIGS. 11

,


12


and


13


schematically illustrate collection of scan data for various number of slices and slice thicknesses.











DETAILED DESCRIPTION OF THE INVENTION




Referring to

FIG. 1

, a computed tomography (CT) imaging system


10


in accordance with one embodiment of the present invention is shown as including a gantry


12


representative of a “third generation” CT scanner. Gantry


12


has an x-ray source


14


that projects a beam of x-rays toward a detector array


16


on the opposite side of gantry


12


. Detector array


16


is formed by a plurality of detector modules which together sense the projected x-rays that pass through a medical patient


18


. Each detector module produces an electrical signal that represents the intensity of an impinging x-ray beam and hence the attenuation of the beam as it passes through patient


18


.




During a scan to acquire x-ray projection data, gantry


12


and the components mounted thereon rotate about a center of rotation. A motorized table


20


positions patient


18


relative to gantry


12


. Particularly, table


20


moves portions of patient


18


through a gantry opening


22


during a scan.




Set forth below is a description of the system hardware architecture, a description of the various scan modes, and a description of an exemplary user interface.




System Hardware Architecture





FIG. 2

is a block schematic diagram of the system illustrated in FIG.


1


. As shown in

FIG. 2

, system


10


includes a host computer


24


coupled to a monitor (user interface)


26


for displaying images and messages to an operator. Computer


24


also is coupled to a keyboard


28


and a mouse


30


to enable the operator to input information and commands to computer


24


. Computer


24


is coupled to a scan and reconstruction control unit (SRU)


32


. SRU


32


also includes image generation controls. In one specific embodiment, SRU


32


includes a SGI PCI-based central processing unit which operates on an IRIX operating system. SRU


32


also includes an interface processor for interfacing with the data acquisition system (described below), and a scan data correction digital signal processing board for performing preprocessing, which is known in the art. SRU


32


also include an image generator for filtered backprojection and postprocessing operations, as is known in the art.




A stationary controller


34


is connected to SRU


32


, and controller


34


is coupled to a table controller


36


. Stationary controller


34


also is connected, through a slipring


38


, to an on-board controller


40


and a scalable data acquisition system (SDAS)


42


. A slipring


38


enables contactless transmission of signals across the slipring boundary and supports the necessary bandwidth for transmission of data and commands across the boundary. SDAS


42


samples and acquires the data from detector


16


and converts the sampled analog signals to digital signals. SDAS


42


, in the specific embodiment, includes forty eight interchangeable converter cards to support four row data acquisition. For two row data acquisition, twenty four cards could be used. In this specific embodiment, there are sixty four input channels per converter card and 1408 Hz sampling can be performed. SDAS


42


also includes a front-end pre-amplifier for amplifying the signals. A forward error correction is applied to the output data.




On-board controller


40


controls operation of x-ray source


14


and operation of SDAS


42


, which converts analog signals to digital data as described above. X-ray source


14


includes a high voltage generator


44


coupled to an x-ray tube


46


. Tube


46


may, for example, be the tube known in the art is the Gemini-1 tube and currently utilized in at least some CT system commercially available from General Electric Company, Milwaukee, Wis. 53201. Beams projected by X-ray tube


46


pass through a prepatient cam collimator


48


and impinge upon detector


16


(illustrated as a


16


row detector). Cam collimator


48


also is controlled by on-board controller


40


. Outputs from detector


16


are supplied to SDAS


42


.




With respect to operation of system


10


, and in

FIG. 2

data flow is illustrated by bold lines, control flow is illustrated by normal lines, and real-time control flow is illustrated by dotted lines. The numeric identifiers associated with the flows are set forth below.






1


: scan and reconstruction prescription from operator






2


: scan prescription to “master” controller






3


: scan parameters distributed






3




a


: table position






3




b


: rotating parameters






3




c


: kV and mA selections






3




d


: x-ray beam collimation and filter selections






3




e


: detector slice thickness and SDAS gain selections






4


: real-time control signals during scanning






5


: high voltage






6


: un-collimated x-ray beam






7


: collimated x-ray beam






8


: analog scan data






9


: digital scan data






10


: patient images Generally rotation of gantry


12


and the operation of x-ray source


14


are governed by controller


34


. On-board controller


40


, under the control of stationary controller


34


, provides power and timing signals to x-ray source


14


. SDAS


42


samples analog data from detector


16


and converts the data to digital signals for subsequent processing. SRU


32


receives sampled and digitized x-ray data from SDAS


42


and performs high speed image reconstruction. The reconstructed image is applied as an input to computer


24


which stores the image in a mass storage device.




Computer


24


also receives commands and scanning parameters from an operator via keyboard


28


and mouse


30


. Monitor


26


allows the operator to observe the reconstructed image and other data from computer


24


. The operator supplied commands and parameters are used by computer


24


to provide control signals and information. In addition, controller


36


controls motorized table


20


to position patient


18


(FIG.


1


).




Scan Modes




Generally, the above described CT system is operable to collect


1


,


2


or more slices data. Axial and helical scans can be performed with the system, and cross section images of a scanned object can be processed, reconstructed, displayed and/or archived. Scalable axial image reconstruction and display refers, for example, to selectability of the image thickness, number of slices, and number of images to be displayed. Further, the system is not limited to practice with any one particular image reconstruction algorithm, and it is contemplated that many different reconstruction algorithms can be utilized. Exemplary algorithms are set forth in U.S. Pat. Nos. 5,469,487, 5,513,236, 5,541,970, 5,559,847, and 5,606,585, and in co-pending U.S. patent application Ser. No. 08/561,382 (filed Nov. 21, 1995), Ser. No. 08/779,961 U.S. Pat. No. 5,828,719 (filed Dec. 23, 1996), and Ser. No. 08/797,101 U.S. Pat. No. 5,983,671 (filed Nov. 26, 1997), all of which are assigned to the present assignee, and all of which are incorporated herein, in their entirety, by reference.




In the axial multi-slice scan mode, multiple rows of scan data can be processed before image reconstruction, and the data can be used to produce either multiple thin slices or a reduced number of thicker slices with reduced image artifact. In addition, images with thicker slice thicknesses can be later reconstructed retrospectively into thinner slices of images based on clinical diagnosis needs. As a result, the number of unwanted images for viewing, filming, and archiving is reduced. In addition, high z-axis resolution images can be later reconstructed for patient diagnosis.




Exemplary axial multi-slice modes are set forth below in Table 1.















TABLE 1











Acquisition Image




Retrospective Reconstruction







Thickness & Mode




Image Thickness Available





























1.25 mm 




4i




1.25, 2.5, 5




mm







2.5 mm




2i




1.25, 2.5, 5




mm







2.5 mm




4i




2.5, 5, 10




mm







3.75 mm 




4i




3.75, 7.5




mm







  5 mm




1i




1.25, 2.5, 5




mm







  5 mm




2i




2.5, 5, 10




mm







  5 mm




4i




5, 10




mm







7.5 mm




2i




3.75, 7.5




mm







 10 mm




1i




2.5, 5, 10




mm







 10 mm




2i




5, 10




mm















As one specific example, and for an axial mode acquisition for a 2.5 mm image thickness in the


2




i


mode, there are several retrospective reconstruction options that can be selected. For example, 4 images having a slice thickness of 1.25 mm can be reconstructed, 2 images having a slice thickness of 2.5 mm can be reconstructed, and 1 image having a slice thickness of 5 mm can be reconstructed. Accordingly, more images (e.g., 4 images) having a thinner slice thickness can be retrospectively reconstructed than the mode (i.e.,


2




i


) in which the scan was performed. In addition, fewer images (e.g., 1 image) having a thicker slice thickness can be retrospectively reconstructed than the mode in which the scan was performed.




Further, and with respect to archiving images, the system enables storage of fewer images which require less storage space. For example, if 20 mm of patient anatomy is scanned in the


2




i


mode, 80 images can be generated. Storing 80 images for 20 mm of patient anatomy requires a large amount of memory. It is often the case that high resolution is not required for the entire 20 mm of patient anatomy. For example, it may be that only about 5 mm of the anatomy requires such high resolution. Using the data collected in 2.5 mm thickness


2




i


mode scan, the operator can retrospectively reconstruct images having a thickness of 5 mm for the majority of the anatomy, and thinner image slices (e.g., 1.25 mm) only at the locations where higher resolution is required. Using this retrospective reconstruction, the number of images to be archived can be significantly reduced.




The above described retrospective reconstruction is provided through the user interface and enabled because the scan data is collected using a multislice detector which is described below in more detail. With the thin slice scan data available, the operator can select from many different slice thicknesses when performing retrospective reconstruction.




In the helical multi-slice scan mode, multiple combinations of patient table speed and x-ray beam and detector collimations, enable generation of images having different z-axis resolution can be produced. For example, at the table speed of 30 mm/rotation, images of 5-10 mm slices can be generated. Thicker slice (such as 10 mm) images can be generated prospectively, which provides the benefit of a reduced number of images and reduced image reconstruction time. At a later time, thinner slice images can be generated retrospectively using the same data. Such thinner slice images may be necessary depending on the clinical application needs. Such thinner slice images can be generated without rescanning the patient.




Exemplary helical multi-slice modes are set forth below in Table 2.













TABLE 2











Table Speed (mm / rotation)




Retrospective Reconstruction













Hi-Q Scan Mode




Hi-Speed Scan Mode




Image Thicknesses Available

















3.75




7.5




1.25, 2.5




mm






7.5




15




2.5, 3.75, 5




mm






11.25




22.5




3.75, 5, 7.5




mm






15




20




5, 7.5, 10




mm














For example, in a high quality image (Hi-Q) scan mode of 3.75 mm/rotation (i.e., the patient table moves 3.75 mm for each gantry rotation), or in a high speed (Hi-Speed) scan mode of 7.5 mm/rotation, images having slice thicknesses of 1.25 mm and 2.5 mm can be reconstructed retrospectively. As with the axial multi-slice mode, many other alternatives are possible depending upon the particular construction of the system components. Again, such flexibility in retrospective reconstruction provides many advantages including enabling the generation of images having the necessary resolution yet reducing the memory necessary for storing the desired images.




Exemplary User Interface





FIG. 3

is an exemplary embodiment of a scan user interface than can be used in conjunction with the system illustrated in

FIGS. 1 and 2

. The interface would be implemented in an instruction set stored in host computer


24


(

FIG. 2

) and displayed on the host computer monitor. At the scan user interface, an operator can select the scan mode, i.e,. helical or axial, as well as the various scan parameter associated with each mode. The selections are made, for example, by the user by simply touching the desired area corresponding to the desired parameters. Touch sensitive interfaces are well known. Of course, many other types of interfaces could be used, and the interface illustrated in

FIG. 3

is only an exemplary interface.




In the helical mode, the operator selects the desired slice thickness, the scan mode, and the scan speed. The “Hi-Q” scan corresponds to a high image quality scan and the “Hi-Speed” scan corresponds to a fast patient table speed, as described above in connection with Table 2. In the axial scan, the operator selects the desired slice thickness and the number of image to be generated per rotation.




Before now, no multi-slice CT system provides the scalable scan management, control, and image reconstruction processes, and scalable image display and analysis, as provided with the present system. With the present system, an operator can readily and simply select the desired number of slices and the slice thickness for images to be displayed. In addition, increased patient scan speed, improved image quality, and reduced x-ray tube loading are achieved.




Additional Component Details




Set forth below is a description of an exemplary scalable multislice CT system components in accordance with one embodiment of the present invention. Although specific component details are set forth below, it should be understood that many alternative embodiments are possible. For example, although one particular detector is described, other detectors could be used in connection with the system, and the present invention is not limited to practice with any one particular type of detector. Specifically, the detector described below includes a plurality of modules and each module includes a plurality of detector cells. Rather than the specific detector described below, a detector which has non-segmented cells along the z-axis, and/or a detector which has multiple modules with multiple elements along the x-axis and/or z-axis can be joined together in either direction to acquire scalable multislice scan data simultaneously, can be utilized.




Particularly, and referring to

FIGS. 4 and 5

, detector


16


includes a plurality of detector modules


50


. Each detector module


50


is secured to a detector housing


52


by plates


54


. Each module includes a multidimensional scintillator array


56


and a high density semiconductor array (not visible). A post patient collimator (not shown) is positioned over and adjacent scintillator array


56


to collimate x-ray beams before such beams impinge upon scintillator array


56


. Scintillator array


56


includes a plurality of scintillation elements arranged in array, and the semiconductor array includes a plurality of photodiodes arranged in an identical array. The photodiodes are deposited, or formed on a substrate


58


, and scintillator array


56


is positioned over and secured to substrate


58


.




Switch and decoder apparatus


60


are coupled to the photodiode array. The photodiodes are optically coupled to scintillator array


56


and have electrical output lines for transmitting signals representative of the light output by scintillator array


56


. Particularly, each photodiode produces a separate low level analog output signal that is a measurement of the beam attenuation for a specific scintillator of scintillator array


56


. The photodiode output lines extend from opposing sides of the semiconductor, or photodiode, array and are connected (e.g., wire bonded) to respective apparatus


60


.




Switch apparatus


60


is a multidimensional semiconductor switch array of similar size as the photodiode array, and switch apparatus


60


is coupled in electric circuit between the semiconductor array and SDAS


42


(FIG.


2


). Apparatus


60


, in one embodiment, includes a plurality of field effect transistors (FETs) arranged as a multidimensional array. Each FET includes an input line electrically connected to one of the respective photodiode output lines, an output line, and a control line (not shown). FET output and control lines are electrically connected to SDAS


42


via a flexible electrical cable


62


. Particularly, about one-half of photodiode output lines are electrically connected to each FET input line one side of the array with the other one-half of photodiode output lines electrically connected to the FET input lines on the other side of the array.




The decoder controls the operation of the FETs to enable, disable, or combine photodiode outputs in accordance with a desired number of slices and slice resolutions for each slice. The decoder, in one embodiment, is a decoder chip or a FET controller as known in the art, and the decoder includes a plurality of output and control lines coupled to the FETs and SDAS


42


. Particularly, the decoder outputs are electrically connected to the switch apparatus control lines to enable the FETs to transmit the proper data. The decoder control lines are electrically connected to the FET control lines and determine which of the outputs will be enabled. Utilizing the decoder, specific FETs are enabled, disable, or have their outputs combined so that specific photodiode outputs are electrically connected to SDAS


42


. Further details regarding detector


16


are set forth in co-pending U.S. patent application Ser. No. 08/978,805, Photodiode Array For A Scalable Multislice Scanning Computed Tomography System, which is assigned to the present assignee and hereby incorporated herein, in its entirety, by reference.




In one specific embodiment, detector


16


includes fifty-seven detector modules


50


. The semiconductor array and scintillator array


56


each have an array size of 16×16. As a result, detector


16


has


16


rows and


912


columns (16×57 modules), which enables


16


simultaneous slices of data to be collected with each rotation of gantry


12


. Of course, the present invention is not limited to any specific array size, and it is contemplated that the array can be larger or smaller depending upon the specific operator needs. Also, detector


16


may be operated in many different slice thickness and number modes, e.g., one, two, and four slice modes. For example, the FETs can be configured in the four slice mode so that data is collected for four slices from one or more rows of the photodiode array. Depending upon the specific configuration of the FETs as defined by decoder control lines, various combinations of photodiode outputs can be enabled, disabled, or combined so that the slice thickness may, for example, be 1.25 mm, 2.5 mm, 3.75 mm, or 5 mm. Additional examples include, a single slice mode including one slice with slices ranging from 1.25 mm thick to 20 mm thick, and a two slice mode including two slices with slices ranging from 1.25 mm thick to 10 mm thick. Additional modes beyond those described are possible.





FIG. 6

illustrates the geometric configuration of the CT system illustrated in FIG.


1


and shows the gantry coordinate system. The coordinate system is referred to in the following figures and is provided only for explanation purposes. Particularly, the x-axis refers to an axis tangent to the circle of rotation of gantry


12


. The y-axis refers to a radial axis extending from the iso center (ISO) of gantry


12


toward the x-ray tube focal spot. The z-axis is a longitudinal axis (in/out) with respect tot he scan plan. The patient is translated along the z-axis on patient table


20


during scanning.




Referring to

FIG. 7

, and in multislice scanning, data is collected at various z-axis locations. Particularly,

FIG. 6

is a schematic illustration of system


10


viewed from a side of the gantry


12


. X-ray tube


46


includes an anode/target


64


and a cathode


66


. An uncollimated x-ray beam


68


is emitted by tube


46


and passes through cam collimator


48


. Collimator


48


includes a bowtie filter


70


and tungsten cams


72


. As explained in connection with

FIG. 2

, the position of cams


72


is controlled by an on-board controller


40


which receives its commands from host computer


24


via SRU


32


and stationary controller


34


. Stepper motors, for example are connected to cams


72


for precisely controlling the position of cams


72


. Cams


72


of cam collimator


48


can be independently adjusted with respect to the spacing between cams


72


and their location relative to the center of the collimator opening depending on the user selected data collection mode.




A collimated x-ray beam


74


is emitted from cam collimator


48


, and beam


74


passes through patient


18


(

FIG. 1

) and impinges upon detector


16


. As described above, detector


16


includes a collimator


76


, a scintillator array


56


, and a photodiode/switching array


78


(the photodiode and switching arrays are shown as one unit in

FIG. 7

but may be separate arrays as described above). Outputs from array


78


are supplied, via a flex cable, to SDAS


42


for processing.




The following description relates to operation of cam collimator


48


and detector


16


for providing scalability in the number of slices and the slice thickness. Although the operation of cam collimator


48


and the operation of detector


16


are sometimes described separately herein, it should be understood that collimator


48


and detector


16


operate in combination to provide the desired number of slices and slice thickness.




More specifically,

FIGS. 8

,


9


, and


10


illustrate operation of cam collimator


48


.

FIG. 8

illustrates cam collimator


48


configured to emit a centered wide beam (e.g., a beam for obtaining 4 slices of data with a 5 mm slice thickness). For a narrow centered beam, and as shown in

FIG. 9

, cams


72


are moved inward an equal amount relative to a center of beam


68


. For example, the cam collimator configured shown in

FIG. 9

could be used for obtaining 4 slices of data with a 1.25 mm slice thickness.




Collimator


48


also can be used to adjust for z-axis beam offset which may occur during operation of tube


46


. Particularly, and referring to

FIG. 10

, cams


72


can be positioned at unequal distances from the center of beam


68


, as indicated by the arrow associated with the legend “cam offset”. By offsetting cams


72


as shown in

FIG. 10

, beam


74


is offset as indicated by the arrow associated with the legend “beam offset”.




As described below in more detail, by controlling the position and width of beam


74


at cam collimator


48


, scans can be performed to obtain data for many different slice numbers and slice thicknesses. For example,

FIG. 11

corresponds to a selected detector configuration when it is desired to obtain 4 slices of data with a slice thickness of 5.0 mm. Cams


72


are separated wide apart in the z-axis direction to provide 20 mm collimation, and the photodiode outputs are combined by switching array


78


into four separate slices. Particularly, each slice of data combines the outputs of four photodiodes into one signal (


1


A,


2


A,


1


B, and


2


B), and each slice data signal (


1


A,


2


A,


1


B, and


2


B) is supplied to SDAS


42


via flex cables


62


.




For four slices of data with a 1.25 mm slice thickness, the detector configuration shown in

FIG. 12

may be utilized. Particularly, cams


72


are not separated as wide apart as for the 5.0 mm slice thickness (FIG.


11


). Rather, cams


72


are separated in the z-axis direction to provide 5 mm collimation, and the photodiode outputs are combined by switching array


78


into four separate slices. Particularly, each slice of data combines the outputs of one photodiodes into one signal (


1


A,


2


A,


1


B, and


2


B), and each slice data signal (


1


A,


2


A,


1


B, and


2


B) is supplied to SDAS


42


via flex cables


62


.




Of course, many other combinations of slice number and slice thickness are possible using system


10


. For example, and referring to

FIG. 13

, for two slices of data with a 1.25 mm slice thickness, cams


72


are separated in the z-axis direction to provide 2.5 mm collimation. The photodiode outputs are combined by switching array


78


into two separate slices. Particularly, each slice of data combines the outputs of one photodiode into one signal (


1


A and


1


B), and each slice data signal (


1


A and


1


B) is supplied to SDAS


42


via flex cables


62


. By controlling cam collimator


48


and channel summation along the z-axis as described above, scan data can be collected for many different slice numbers and slice thicknesses.




Many variations and additions to the above described exemplary system can be made. For example, a graphic based user interface which enables the user to easily prescribe multislice scan and image reconstruction in various forms with, for example, optimum table speed, x-ray beam collimation, data collection slice thickness, x-ray beam voltage and current values, as well as the reconstruction method to obtain the desired image quality. Such an interface may be activated by a touch screen, voice, or other known interface methodologies that are easy to use and understand. The host computer can be preprogrammed to include various default modes based upon the type of scan being performed to further simplify the operator performed selections.




Again, the above described multislice CT system can be used to collect one, two or more slices of data to provide enhanced flexibility. Such system also enables fast scanning speed with good image quality and z-axis resolution, with a low x-ray tube load. Further, and using the system, the operator can easily and quickly prescribe multislice scan and image reconstruction parameters.




From the preceding description of various embodiments of the present invention, it is evident that the objects of the invention are attained. Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. Accordingly, the spirit and scope of the invention are to be limited only by the terms of the appended claims.



Claims
  • 1. A method for generating an image in a scalable multi-slice computed tomography system, said method comprising the steps of:performing a scan based on at least one selected scan parameter; and retrospectively reconstructing an image using the stored scan data, wherein the scan parameter comprises a first slice thickness and wherein the image reconstruction reconstructs an image having a second slice thickness, and wherein the first slice thickness is different from the second slice thickness.
  • 2. A method in accordance with claim 1 wherein the scan parameter comprises table speed.
  • 3. A method in accordance with claim 1 wherein the scan parameter for the helical scan comprises a high image quality scan mode.
  • 4. A method in accordance with claim 1 wherein the scan parameter for the helical scan comprises a high speed scan mode.
  • 5. A method in accordance with claim 1 wherein the scan parameter for the helical scan comprises at least one of a scan speed, a high image quality scan mode, and a high speed scan mode.
  • 6. In a scalable multi-slice computed tomography system, a user interface configured for enabling a user to select at least one scalable scan parameters including a first slice thickness, and for enabling a user to select a second slice thickness for image reconstruction, said second slice thickness being different from said first slice thickness.
  • 7. An interface in accordance with claim 6 wherein said scan parameter comprises slice thicknesses for multiple slice scans.
  • 8. An interface in accordance with claim 6 wherein said scan parameter for a helical scan comprises a scan speed.
  • 9. An interface in accordance with claim 6 wherein said scan parameter for a helical scan comprises a high image quality scan mode.
  • 10. An interface in accordance with claim 6 wherein said scan parameter for a helical scan comprises a high speed scan mode.
  • 11. An interface in accordance with claim 6 wherein said scan parameter for a helical scan comprises a scan speed, a high image quality scan mode, and a high speed scan mode.
  • 12. An interface in accordance with claim 6 wherein said scan parameter for an axial scan further comprises a number of images per rotation.
  • 13. A method for generating an image in a scalable multi-slice computed tomography system, said method comprising the steps of:performing a scan based on at least one selected scan parameter; collecting multislice scan data by performing a scan based at least in part on the scan parameter; and retrospectively reconstructing images corresponding to a first anatomy area in accordance with a first reconstruction option; and reconstructing images corresponding to a second anatomy area in accordance with a second reconstruction option.
  • 14. A method for generating an image in a scalable multi-slice in accordance with claim 13 wherein the first reconstruction option is a first slice thickness and the second reconstruction option is a second slice thickness.
  • 15. A method for generating an image in a scalable multi-slice in accordance with claim 13 wherein the first slice thickness and the second slice thickness are different.
CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/083310, filed Apr. 28, 1998.

US Referenced Citations (23)
Number Name Date Kind
4965726 Heuscher et al. Oct 1990
5188110 Sugimoto Feb 1993
5291402 Pfoh Mar 1994
5430783 Hu et al. Jul 1995
5469487 Hu Nov 1995
5513236 Hui Apr 1996
5541970 Hu Jul 1996
5559847 Hu et al. Sep 1996
5606585 Hu Feb 1997
5625661 Oikawa Apr 1997
5668846 Fox et al. Sep 1997
5684855 Aradate Nov 1997
5732118 Hsieh Mar 1998
5734691 Hu et al. Mar 1998
5828719 He et al. Oct 1998
5845003 Hu et al. Dec 1998
5864598 Hsieh et al. Jan 1999
5974110 Hu Oct 1999
5982846 Toth et al. Nov 1999
6023494 Senzig et al. Feb 2000
6039047 Rock et al. Mar 2000
6061420 Strong et al. May 2000
6081576 Schanen et al. Jun 2000
Foreign Referenced Citations (2)
Number Date Country
198 53 646 A1 May 1999 DE
0 981 999 A2 Mar 2000 EP
Provisional Applications (1)
Number Date Country
60/083310 Apr 1998 US