U.S. patent application number 10/675299 was filed with the patent office on 2004-04-01 for imaging of pixel defects in digital detectors.
This patent application is currently assigned to General Electric Company. Invention is credited to Aufrichtig, Richard, French, John C., Kwasnick, Robert Forrest, Lamberty, John R..
Application Number | 20040061785 10/675299 |
Document ID | / |
Family ID | 23170921 |
Filed Date | 2004-04-01 |
United States Patent
Application |
20040061785 |
Kind Code |
A1 |
Aufrichtig, Richard ; et
al. |
April 1, 2004 |
Imaging of pixel defects in digital detectors
Abstract
A method and apparatus for displaying an image generated by at
least one detector of an imaging unit are disclosed herein. The
method includes creating a pixel map identifying locations of bad
pixels in an array of pixels in the image detected by the at least
one detector, linking the pixel map to the image, and providing for
selective display of the pixel map. Bad pixels behave from a group
including pixels which do not respond electrically and pixels which
are statistically different from surrounding pixels in the array of
pixels. The apparatus includes an imaging unit for generating
x-rays which pass through a body of interest, at least one detector
unit for detecting the x-rays, and a processing unit for
identifying bad pixels within the detected image.
Inventors: |
Aufrichtig, Richard;
(Mountain View, CA) ; Kwasnick, Robert Forrest;
(Palo Alto, CA) ; Lamberty, John R.; (Oconomowoc,
WI) ; French, John C.; (Wauwatosa, WI) |
Correspondence
Address: |
GE MEDICAL SYSTEM
C/O FOLEY & LARDNER
777 EAST WISCONSIN AVENUE
MILWAUKEE
WI
53202-5367
US
|
Assignee: |
General Electric Company
|
Family ID: |
23170921 |
Appl. No.: |
10/675299 |
Filed: |
September 30, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10675299 |
Sep 30, 2003 |
|
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09303190 |
Apr 30, 1999 |
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6661456 |
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Current U.S.
Class: |
348/207.99 ;
348/E17.002; 348/E5.081; 348/E5.086 |
Current CPC
Class: |
H04N 5/367 20130101;
H04N 17/002 20130101; A61B 6/583 20130101; H04N 5/32 20130101 |
Class at
Publication: |
348/207.99 |
International
Class: |
H04N 005/225 |
Claims
What is claimed is:
1. A method for displaying an image generated by at least one
detector of an imaging unit, the method comprising: creating a
pixel map identifying locations of bad pixels in an array of pixels
in the image detected by the at least one detector, the bad pixels
behaving from a group including pixels which do not respond
electrically and pixels which are statistically different from
surrounding pixels in the array of pixels; linking the pixel map to
the image; and providing for selective display of the pixel map
over the image by a user selecting a display of at least a portion
of the created pixel map.
2. The method of claim 1, wherein the providing step includes
providing a graphical overlay with graphical symbolic
representations of the bad pixels superimposed on the image.
3. The method of claim 1, further comprising communicating the
image to a storage unit, wherein information identifying the bad
pixels is communicated as an image header.
4. The method of claim 1, further comprising communicating the
image to a computer, wherein information identifying the bad pixels
is communicated for use by image analysis algorithms executed by
the computer, wherein the bad pixels are not mistaken for a
clinical pathology.
5. The method of claim 1, wherein the providing step includes
providing a textual display with information identifying the bad
pixels.
6. The method of claim 1, further comprising selecting an area of
the image, wherein the providing step includes displaying the bad
pixels within the selected area.
7. An apparatus for displaying an image generated by at least one
detector of an imaging unit, the apparatus comprising: means for
creating a pixel map identifying locations of bad pixels in an
array of pixels in the image detected by the at least one detector,
the bad pixels behaving from a group including pixels which do not
respond electrically and pixels which are statistically different
from surrounding pixels in the array of pixels; means for linking
the pixel map to the image; and means for providing for selective
display of the pixel map. Over the image selected by a user
selecting a display of at least a portion of the created pixel
map.
8. The apparatus of claim 7, wherein the means for providing
includes means for providing graphical symbolic representations of
the bad pixels superimposed on the image.
9. The apparatus of claim 7, further comprising means for
communicating the image to a storage unit, wherein information
identifying the bad pixels is communicated.
10. The apparatus of claim 7, wherein the image is a clinical
image.
11. The apparatus of claim 10, further comprising means for
communicating the image to a computer wherein information
identifying the bad pixels is communicated for use by image
analysis algorithms executed by the computer, wherein the bad
pixels are not mistaken for a clinical pathology.
12. The apparatus of claim 7, wherein the means for providing
includes means for providing a textual display with information
identifying the bad pixels.
13. An apparatus for displaying an image, the apparatus comprising:
an imaging unit for generating x-rays which pass through a body of
interest having a structure; at least one detector unit for
detecting the x-rays which pass through the body of interest to
form an image, the image including an array of pixels which contain
information on the structure; a processing unit coupled to the at
least one detector unit, the processing unit configured to identify
bad pixels within the array of pixels in the image formed by the at
least one detector unit, the bad pixels behaving from a group
including pixels which do not respond electrically and pixels which
are statistically different from surrounding pixels in the array of
pixels; and a display coupled to the processing unit and providing
visual display of the image and selectively displaying the bad
pixels over the image.
14. The apparatus of claim 13, wherein the display selectively
displays the bad pixels by providing a graphical overlay with
graphical symbolic representations of the bad pixels superimposed
on the image.
15. The apparatus of claim 13 further comprising an operator input
device for selecting an area of the image, wherein the display
selectively displays the bad pixels within the selected area of the
image.
16. The apparatus of claim 13, wherein the image is a clinical
image and the processing unit is further configured to link
information identifying the bad pixels to the image, wherein image
analysis algorithms executed to analyze the image do not mistake
the bad pixels for a clinical pathology.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 09/303,190, the disclosure of which is
incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to imaging systems.
More particularly, the present invention relates to a digital
imaging system equipped to detect and display defects contained
within the imaging detector.
[0003] Imaging systems include systems where images are generated
by, x-ray, magnetic resonance imaging (MRI), ultrasound,
computerized tomography (CT), or such nuclear medicine techniques
as positron emission tomography (PET) or single photon emission
computerized tomography (SPECT). In each system, a source of
electromagnetic radiation (e.g., x-rays) emits radiation which
passes through a body of interest and is detected by some kind of
detector. Various structures of various densities in the body of
interest absorb the radiation differently, such that the radiation
detected by the detector provides information on the
structures.
[0004] Imaging systems are often used to provide detailed
information on structures inside the human body. For example, CT
scans of the head are useful for evaluation of head injury and
detection of tumor, stroke, or infection. Imaging devices are also
useful for the detection of pathologies, or manifestations of
diseases such as cancer.
[0005] Conventional digital image detectors are, nevertheless,
known to lose image information at locations in the detected image
which contain a detector defect. These defects are typically called
"bad pixels." In general, bad pixels are image elements which
either do not respond electrically or have a behavior that is
statistically different from surrounding pixels in the detector
array.
[0006] Generally, detection of bad pixels in an imaging system is
accomplished by imaging a standard set of test phantoms, such as
flat fields, with predetermined imaging techniques. Depending on
the number of bad pixels and their proximity to other bad pixels in
the detected image, clusters of bad pixels may result and
clinically relevant information may be lost.
[0007] Thus, there is a need to alert the user of imaging systems
as to the location of bad pixels and/or clusters of bad pixels in
the displayed image. Further, there is a need to avoid medical
misdiagnosis caused by unawareness of detector defects. Even
further, there is a need to provide critical information to
algorithms which are used to detect local statistical image
variations which may mistakenly quantify detector defects as
pathologies.
BRIEF SUMMARY OF THE INVENTION
[0008] One embodiment of the invention relates to a method for
displaying an image generated by at least one detector of an
imaging unit. The method includes creating a pixel map identifying
locations of bad pixels in an array of pixels in the image detected
by the at least one detector, linking the pixel map to the image,
and providing for selective display of the pixel map. Bad pixels
include pixels which do not respond electrically and/or pixels
which are statistically different from surrounding pixels in the
array of pixels.
[0009] Another embodiment of the invention relates to an apparatus
for displaying an image generated by at least one detector of an
imaging unit. The apparatus includes means for creating a pixel map
identifying locations of bad pixels in an array of pixels in the
image detected by the at least one detector, means for linking the
pixel map to the image, and means for providing for selective
display of the pixel map. Bad pixels include pixels which do not
respond electrically and/or pixels which are statistically
different from surrounding pixels in the array of pixels.
[0010] Another embodiment of the invention relates to an apparatus
for displaying an image. The apparatus includes an imaging unit, at
least one detector unit, a processing unit, and a display. The
imaging unit generates x-rays which pass through a body of interest
having a structure. The at least one detector unit detects the
x-rays which pass through the body of interest to form an image.
The image includes an array of pixels which contain information on
the structure. The processing unit is coupled to the at least one
detector unit and identifies bad pixels within the array of pixels
in the image formed by the at least one detector unit. Bad pixels
include pixels which do not respond electrically and/or pixels
which are statistically different from surrounding pixels in an
array of pixels. The display is coupled to the processing unit and
provides visual display of the image and selectively displays the
bad pixels.
[0011] Other principle features and advantages of the present
invention will become apparent to those skilled in the art upon
review of the following drawings, the detailed description, and the
appended claims.
DESCRIPTION OF THE DRAWINGS
[0012] The invention will become more fully understood from the
following detailed description, taken in conjunction with the
accompanying drawings, wherein like reference numerals denote like
elements, in which:
[0013] FIG. 1 is a general block diagram of an x-ray imaging system
in accordance with the present invention;
[0014] FIG. 2 is a display of an exemplary image in an embodiment
of the x-ray detector system of FIG. 1;
[0015] FIG. 3 is a pixel map including detected bad pixels in the
displayed image of FIG. 2;
[0016] FIG. 4 is the display of FIG. 2 including a grid showing the
displayed image divided into an array of pixels;
[0017] FIG. 5 is a block diagram of a file in a second embodiment
of the x-ray detector system of FIG. 1;
[0018] FIG. 6 is a display of an exemplary image in a third
embodiment of the x-ray detector system of FIG. 1; and
[0019] FIG. 7 is a flow chart of an exemplary method used to
visualize bad pixels in the image detected by the detector of the
system shown in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0020] FIG. 1 is a general block diagram of an x-ray imaging system
100. System 100 includes an x-ray unit 110, a digital x-ray
detector 120, a local computer or processing unit 130, a local
image review station 140, a storage unit 150, and a remote image
review station 160. X-ray unit 110 is an x-ray generating unit
which includes an x-ray generator and x-ray tube. X-ray unit 110
generates x-rays which pass through a body of interest (e.g., part
of a human body).
[0021] In alternative embodiments, imaging system 100 is any of a
variety of imaging systems (e.g., ultrasound). Such alternative
embodiments include components characteristic to the particular
type of imaging system used.
[0022] After passing through the body of interest, the x-rays from
x-ray unit 110 are detected by digital x-ray detector 120, which
forms an image from the x-rays. The image detected by detector 120
includes an array of pixels, or image elements, which contain
information on the detected x-rays and, thus, of the structures
within the body of interest. Detector 120 includes electronics for
communicating data on the x-rays to other devices.
[0023] Processing unit 130 is any of a variety of programmable
electronic machines which performs operations or assembles, stores,
correlates, or otherwise processes information. In one embodiment,
processing unit 130 is a computer. Processing unit 130 processes
the x-ray data from detector 120. Processing unit 130 is coupled to
detector 120 and identifies bad pixels within the array of pixels
in the image detected by detector 120. Bad pixels are pixels that
either do not respond electronically or are statistically different
from surrounding pixels in the array of pixels.
[0024] Local image review station 140 includes a display and
controls. Local image review station 140 is coupled to processing
unit 130 and provides graphical and/or textual display of x-ray
imaging data from x-ray unit 110 and digital x-ray detector 120.
Controls on local image review station 140 allow a reviewer to
change a variety of display options. For example, station 140 can
be configured by the reviewer to selectively display a map of bad
pixels superimposed on the image.
[0025] Storage unit 150 is coupled to any one of processing unit
130 and station 140. Storage unit 150 is preferably a disk drive
for storing digital information. Storage unit 150 is alternatively
a solid state storage device or any other memory component capable
of maintaining data displayed on local image review station 140.
Further still, storage unit 150 is alternatively integrated into
processing unit 130. Storage unit 150 maintains x-ray imaging data
in the form of an image file. Thus, x-ray imaging data is available
for later retrieval either by local station 140 or remote station
160.
[0026] Remote image review station 160 includes a display and
controls. Remote image review station 160 is similar to local
review station 140 in that station 160 provides graphical and/or
textual display of x-ray imaging data from x-ray unit 110. Further,
controls allow a reviewer to change a variety of display options.
For example, station 160 provides for the selective display of a
map of bad pixels. Remote station 160 is coupled to local image
review station 140 or storage unit 150 by a network 165. Network
165 is a local area network (LAN), wide area network (WAN),
synchronous optical network (SONET), or any other interconnection
of electronic components for sharing information.
[0027] Station 160 advantageously provides doctors or other trained
personnel located remotely from x-ray unit 110 with access to
graphical and textual display of x-ray imaging data. Station 160
obtains x-ray imaging data either from local station 140 or from
archived copies in storage unit 150.
[0028] Alternatively, system 100 includes a plurality of detectors
120, forming an array of detectors. Where an array of detectors is
used, one image is obtained from the plurality of detectors. The
one image from the plurality of detectors 120 is processed by
processing unit 130 and displayed by station 140 or station 160.
For example, a CT device includes an array of detectors arranged
along the inside perimeter of a slip ring. The one image from the
plurality of detectors may include bad pixels in the image due to
defects in one or multiple detectors.
[0029] In an exemplary embodiment, local image review station 140
and remote image review station 160 each include a display unit
200. FIG. 2 illustrates display unit 200 including a display 210, a
defective pixel map overlay control 220, a select area query
control 230, and a power switch 240.
[0030] Display 210 is a cathode ray tube (CRT) display, thin film
transistor (TFT) display, or any other device for displaying
images. Display 210 shows an image of a human chest using x-ray
unit 110 in a defective pixel map overlay mode. In defective pixel
map overlay mode, display unit 200 displays the clinical image of
the chest with a defective pixel map overlay. The overlay includes
an operator selection of white, black, color-coded, or alternative
symbols to identify bad pixel locations. Where color coding is
used, different colors characterize different detector defects. A
color coding index is available at station 140.
[0031] In the embodiment of FIG. 2, display 210 is a black and
white display that reveals detector pixel defects 250 in reverse
color on the image. For example, where the image on display 210 is
white, pixel defects are shown in black and, where the image on
display 210 is black, pixel defects are shown in white. The image
shown in display 210 (including defective pixels) can be output to
a laser printer or other printing device.
[0032] Controls 220 and 230 are buttons on display unit 200 which
allow the image reviewer to select one of two pixel defect display
modes. In the first pixel defect display mode, the image reviewer
is shown display 210 with a defective pixel map overlaying the
image. In the second pixel defect display mode, the image reviewer
is shown display 210 and allowed to select areas on the display in
order to query whether those areas contain bad pixels. Controls 220
and 230 are alternatively included as touch-screen buttons on
display 210, selections in a menu bar on display 210, or any other
arrangement in the user interface of display unit 200. Power switch
240 is an on/off button activating or deactivating display unit
200.
[0033] FIG. 3 is a pixel map 300 which can be displayed on display
unit 200. Pixel map 300 includes bad pixels 350 within an array of
pixels. Bad pixels 350 are identified by processing unit 130 as
pixels which either do not respond electronically or behave in a
manner which is statistically different from surrounding pixels in
the array of pixels. The locations of bad pixels 350 are included
in the image file of storage unit 150 as row and column locations
in the array of pixels.
[0034] FIG. 4 illustrates a display unit 400 including a pixel grid
460. Pixel grid 460 is not displayed on display 410, rather it is
used in FIG. 4 to illustrate the division of the image displayed by
display 410 into an array of pixels. Pixel defects 450 are single
bad pixels or clusters of bad pixels in the image. The locations of
pixel defects 450 are included in an information header of the
image file stored in storage unit 150 as row and column
locations.
[0035] FIG. 5 is a block diagram of an exemplary file 500 of x-ray
detector system 100. File 500 is a computer file, linked list,
array, or any other data structure for arranging and storing
information. File 500 includes an image header 510 and image data
520. Image header 510 contains data representative of the locations
of detected bad pixels and clusters (e.g., row and column indicia
for each defect). Image data 520 contains data representative of
the clinical image, such as image data for the human chest of FIG.
2. File 500 is formatted in text, HTML, ASCII, or any of a variety
of file formats.
[0036] Image header 510 provides a link of bad pixel data to a
corresponding image. Linking the bad pixel data with a
corresponding image advantageously provides access to reliable
image information for both currently displayed images and archived
image files.
[0037] FIG. 6 illustrates a display unit 600 in another embodiment
of x-ray detector system 100. Display unit 600 includes a display
610, a defective pixel map overlay control 620, a select area query
control 630, and a power switch 640. Display 610, controls 620 and
630, and power switch 640 are substantially the same as display
210, controls 220 and 230, and power switch 240 in FIG. 2.
[0038] Display 610 provides a graphical image of a human chest
using x-ray unit 110 in a select area query mode. In the select
area query mode, a, reviewer of the image selects an area using,
for example, a mouse cursor 660 controlled by a mouse input device
670. After selection of an area using input device 670, a dashed
box 680 is displayed to indicate the particular area selected.
Alternatively, the reviewer of the image selects an area on the
image by touching the screen at that area, creating a box around
the area using a computer mouse, or any of a variety of user
interface arrangements.
[0039] Once the area in question is selected, display unit 600
displays whether the selected area contains a bad pixel or cluster
of bad pixels, such as pixel defects 650, by displaying a graphical
area overlay similar to that used in defective pixel map overlay
mode (FIG. 2) in the selected area or by giving a graphical or
textual indication as to whether a bad pixel is present in the
selected area. For example, a text message "NO DEFECTIVE PIXELS IN
AREA" is alternatively displayed for selected areas without bad
pixels. Display 610 can be output to a laser printer or other
printing device.
[0040] FIG. 7 is a flow chart 700 of an exemplary method used to
visualize bad pixels in the image detected by detector 120 of x-ray
detector system 100. In a step 710, standard imaging techniques are
used to identify bad pixels, or image elements, within an array of
pixels in the image detected by detector 120. Bad pixels are pixels
that either do not respond electrically or have a behavior that is
statistically different from surrounding pixels in the array of
pixels. A map of the detected bad pixels identified is stored in
processing unit 130. Standard imaging techniques for identifying
bad pixels include, for example, those disclosed in U.S. Pat. No.
5,657,400 issued to Granfors et al.; U.S. Pat. No. 5,854,655 issued
to Watanabe, et al.; U.S. Pat. No. 5,272,536 issued to Sudo et al.;
and U.S. Pat. No. 5,047,863 issued to Pape, et al.
[0041] After step 710, a step 715 is performed in which the
operator of local image review station 140 selects the desired type
of bad pixel display. The operator preferably chooses either an
overlay display using control 220, 420 or 620 or a selected area
display using control 240, 440 or 640. If the operator chooses an
overlay display, a step 720 is performed. If the operator chooses a
selected area display, a step 730 is performed.
[0042] In step 720, the bad pixel map is displayed overlaying the
clinical image acquired by detector 120 on local image review
station 140. An example of an overlay display is shown in FIG.
2.
[0043] In step 730, the operator selects a clinically suspicious
area on the clinical image using a mouse cursor, keyboard keys, or
other types of controls. A clinically suspicious area may be one
which includes lone graphical aberrations in the image,
inconsistent patterns in the image, or other image anomalies.
[0044] Defects in the selected area are preferably displayed using
a graphical overlay for the selected area. An example of a selected
area display including mouse cursor 660 is shown in FIG. 6.
Further, a text message is alternatively displayed indicating the
presence or absence of defective pixels within the selected area.
Alternatively, a numerical value representing the quality of the
detector in the selected area is displayed. The numerical value
represents, for example, the number of bad pixels within the
selected area.
[0045] After step 720 or 730, a step 740 is performed in which the
clinical image of x-ray unit 110 is archived locally onto storage
unit 150. A bad pixel map identified by processing unit 130 is
included with the clinical image as an information field in the
information header of the image file and stored in storage unit
150. An example of an image file is shown in FIG. 5.
[0046] As such, header information including the location of bad
pixels in the array of pixels displayed is available for advanced
imaging algorithms. The algorithms use the location of bad pixel
information to avoid mistaking a defect for a clinical pathology or
enhancing a defect during manipulation by the algorithm. Advanced
imaging algorithms include algorithms for computer assisted
diagnosis (CAD) or other digital image enhancement methods.
[0047] After step 740, a step 745 is performed to determine if
x-ray detector system 100 is networked to remote image review
station 160. If so, a step 750 is performed in which the clinical
image, including the bad pixel map in the image header, is
communicated to remote image review station 160 by network 165.
Steps 715, 720, and 730 are performed at remote image review
station 160 to provide display of bad pixels in the clinical image
in a similar fashion to the display at local review station
140.
[0048] X-ray detector system 100 discussed in reference to FIGS.
1-6 and the method discussed with reference to FIG. 7
advantageously provide selective display of bad pixels (and/or
clusters of bad pixels) in the image detected by detector 120.
Further, system 100 links images from x-ray unit 110 with a map of
corresponding bad pixels detected on detector 120 by processing
unit 130.
[0049] Thus, human reviewers of the image and computer algorithms
analyzing the image are provided with information which identifies
bad detector pixels. As such, bad pixels are not mistaken for
clinical pathologies either by human reviewers or computer
programs. Further, bad pixels are not enhanced by CAD algorithms.
Therefore, x-ray defector system 100 and systems utilizing the
method discussed above are more reliable and more effective imaging
systems.
[0050] While the embodiments illustrated in the FIGURES and
described above are presently preferred, it should be understood
that these embodiments are offered by way of example only. Other
embodiments may include, for example, data structures other than
arrays to contain information from x-ray unit 110. Further, the
term pixel should be understood to include any image or picture
element. For purposes of the present invention, the use of the term
"pixel" may be interpreted to include picture or image elements,
and, depending on the application, may represent a voxel or
predefined area or volume. "Pixel" should not be limited to a
single picture or image element, elements necessarily arranged in a
matrix, or an element of a particular size or shape. The invention
is not limited to a particular embodiment, but extends to various
modifications, combinations, and permutations that nevertheless
fall within the scope and spirit of the appended claims.
* * * * *