WO2004061480A1 - Method and apparatus to recover a dead pixel in digital imaging systems - Google Patents
Method and apparatus to recover a dead pixel in digital imaging systems Download PDFInfo
- Publication number
- WO2004061480A1 WO2004061480A1 PCT/IB2004/000011 IB2004000011W WO2004061480A1 WO 2004061480 A1 WO2004061480 A1 WO 2004061480A1 IB 2004000011 W IB2004000011 W IB 2004000011W WO 2004061480 A1 WO2004061480 A1 WO 2004061480A1
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- WO
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- Prior art keywords
- radiation
- defective
- token
- set forth
- event
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims description 18
- 238000003384 imaging method Methods 0.000 title description 7
- 230000005855 radiation Effects 0.000 claims abstract description 79
- 230000002950 deficient Effects 0.000 claims abstract description 40
- 230000004044 response Effects 0.000 claims description 4
- 239000013078 crystal Substances 0.000 claims description 3
- 238000001514 detection method Methods 0.000 claims 1
- 230000001678 irradiating effect Effects 0.000 claims 1
- 238000012544 monitoring process Methods 0.000 claims 1
- 239000007787 solid Substances 0.000 claims 1
- 238000009826 distribution Methods 0.000 description 5
- 229940121896 radiopharmaceutical Drugs 0.000 description 5
- 239000012217 radiopharmaceutical Substances 0.000 description 5
- 230000002799 radiopharmaceutical effect Effects 0.000 description 5
- 230000004075 alteration Effects 0.000 description 2
- 238000003491 array Methods 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000013500 data storage Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012633 nuclear imaging Methods 0.000 description 2
- 230000003412 degenerative effect Effects 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 210000000056 organ Anatomy 0.000 description 1
- 230000008569 process Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/20—Measuring radiation intensity with scintillation detectors
- G01T1/2018—Scintillation-photodiode combinations
- G01T1/20184—Detector read-out circuitry, e.g. for clearing of traps, compensating for traps or compensating for direct hits
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
- A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
- A61B6/4208—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
- A61B6/4258—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector for detecting non x-ray radiation, e.g. gamma radiation
Definitions
- the present invention relates to the art of digital imaging. It finds particular application in nuclear cameras, and will be described with particular reference thereto. It is to be appreciated that the present invention is applicable to other pixilated imaging devices, such as astronomy detectors for image faint regions of space. Those skilled in the art will appreciate applicability of the present invention in the applications where presence of dead or degenerative pixels destroys the precision of the methodology.
- Diagnostic nuclear imaging is used to study a radionuclide distribution in a subject.
- one or more radiopharmaceutical or radioisotopes are injected into a subject.
- the radiopharmaceutical is commonly injected into the subject's bloodstream for imaging the circulatory system or for imaging specific organs, which absorb the injected radiopharmaceutical.
- a radiation detector is placed adjacent to the surface of the subject to monitor and record emitted radiation. Often, the detector is rotated or indexed around the subject to monitor the emitted radiation from a plurality of directions. These projection data sets are reconstructed into a three-dimensional image representative of the radiopharmaceutical distribution within the subject.
- each detector head includes an array of photomultiplier tubes (PMTs) facing a large scintillation crystal.
- PMTs photomultiplier tubes
- Each radiation event generates a corresponding flash of light that is seen by the closest photomultiplier tubes.
- Each photomultiplier tube that sees an event puts out a corresponding analog pulse.
- the analog pulses from the individual PMT's are digitized and combined to generate x and y spatial coordinates of the location of scintillation event on the crystal face.
- the solid- state array generally includes approximately 15,000 pixels or more of 1 to 2mm. It is difficult to manufacture an array this size without any dead or out of specification pixels. Moreover, in use over time, one or more pixels often become dead, degenerate, or otherwise fail to provide a correct data in response to a radiation event. Pixels that do not generate correct data cause artifacts in the reconstructed image.
- a radiation detecting apparatus is provided.
- An array of elements converts individual received radiation events into corresponding radiation event signals.
- One of the radiation converting elements is defective.
- a means digitizes the radiation events.
- a means generates radiation event signals for the defective radiation converting element based on the radiation event signals from the other radiation converting elements of the array.
- a method of detecting radiation is provided. Radiation events are received at an array of pixilated locations and corresponding radiation event signals are generated. At least one of the locations is defective. The radiation event signals from the non-defective locations are digitized. Radiation event signals for the defective location are generated based on the radiation event signals from the non-defective locations.
- the invention may take form in various components and arrangements of components, and in various steps and arrangements of steps.
- the drawings are only for purposes of illustrating the preferred embodiments and are not be construed as limiting the invention.
- FIGURE 1 is a diagrammatic illustration of a nuclear digital imaging device in accordance with the present invention.
- FIGURE 2 is a diagrammatic illustration of the radiation event signal generating circuitry
- FIGURE 3 illustrates a technique for generating radiation event signals for defective pixels
- FIGURE 4 illustrates an alternative embodiment of the random event generating technique
- FIGURE 5 illustrates a technique for generating radiation event signals for a pair of side-by-side defective pixels.
- a nuclear imaging device typically includes a stationary gantry 10 that supports a rotating gantry 12.
- One or more detector heads 14 are carried by the rotating gantry to detect radiation events emanating from a region of interest 16.
- Each detector head includes a two-dimensional array 18 of detector elements.
- the detector arrays are preferably solid-state detectors, which convert gamma radiation directly into electrical charge.
- other arrays such as an array of scintillators optically coupled with an array of photodiodes, or the like are also contemplated.
- Each head includes circuitry 20 for converting each radiation response into a digital signal indicative of its location (x, y) on the detector face and its energy (z).
- an object 22 to be imaged is injected with one or more radiopharmaceutical or radioisotopes and placed in the examination region 16.
- the presence of these pharmaceuticals within the obj ect 22 produces emission radiation from the obj ect.
- Radiation traveling along a traj ectory defined by a collimator 24 is detected by the detector heads 14.
- the detector heads are angularly indexed or rotated around the examination region to collect the emission data from a plurality of directions.
- the projection emission data (x, y, z) and an angular position ( ⁇ ) of the detector head around the examination region are stored in a data storage 24.
- a reconstruction processor 28 processes the event and detector orientation data from the data storage 26 into a volumetric image representation.
- the image representation is then stored at a volume image memory 30 for manipulation by a video processor 32 and display on an image display 34 such as a video monitor, printer, or the like.
- the circuitry 20 optionally includes an array 40 of signal processing circuitry for amplifying, or otherwise processing the output of each detector element of the array 18.
- An array 42 of analog-to-digital converters convert each event to a digital signal indicative of an (x,y) position on the detector face and which digitizes a pulse amplitude to provide an energy signal (z).
- the detector face is irradiated with a uniform flood field. With a uniform flood of radiation, all detectors of the array should have the same number of counts and the events should be of consistent amplitude.
- a control circuit or processor 44 monitors the output of each detector element, either directly or by reading the memory 26 to see if each has substantially the same number of counts and substantially the same energy distribution. If any of the detectors differ from the others by more than a preselected deviation, the control processor 44 causes a switching means 46 to delete signals form the malfunctioning elements or causes the preamplifiers 40 to disconnect the malfunctioning elements (e.g., pixel P0) from the analog-to-digital converter 42.
- the control processor 44 also causes the outputs of a plurality of nearest neighbors or other contributing pixels (e.g., pixels P1-P8) to be sent both to memory 26 and an event generation circuit 48.
- the output of the event generation circuit 48 is connected with the data memory 26 to supply (x, y, z) radiation events for the malfunctioning elements in accordance with events received by the contributing pixels.
- the event generator 48 of the preferred embodiment includes an input 50 in which events from each contributing pixel, e.g., the nearest neighbor pixels (Pl- P8) are received.
- a look-up and compare circuit 52 looks at a corresponding pixel table 54 and deterrnines whether the contributing pixel at which an event occurred corresponds to a table position which has a token 56.
- the token 56 is in table position PI corresponding to nearest neighbor PI, then when an input event is received from the pixel PI, the look-up and compare circuit 52 produces an output indicative of a received event at position PO.
- the back-up and compare circuit 52 further enables a token passing control circuit 58 to cause the table location PI to pass the token to one of table locations P2-P8 corresponding to the other contributing pixels.
- the token may be passed among the table locations in order, it is preferred that it be passed randomly. In this manner, if there are eight contributing pixels, approximately l/8 a ⁇ of the events occurring at each of the contributing pixels will be credited not only to the contributing pixel location, but also to the location of the defective pixel.
- the energy of the contributing pixel event is passed to the data memory as the energy of the event at PO.
- an energy circuit 60 replace the actual energy of the shared event with an average expected energy of the injected radioisotope. More specifically, the energy of the events is generally distributed over a bell-shaped curve.
- a dither circuit 62 preferably oscillates the energy along the bell-shaped curve to create a more typical energy distribution.
- the dithering circuit 62 deletes 70 the least significant bits of the energy value from the contributing pixel, e.g., the three least significant bits.
- the dithering circuit 60 includes a random number generator 72 for generating random values for the detected least significant bits which replace 74 the deleted bits.
- the contributing pixels need not be the eight nearest neighboring pixels.
- the contributing pixels include the 24 nearest neighboring pixels.
- the token passing circuit 58 passes the token based on proximity of the contributing pixels. The randomness of the token passing algorithm is selected such that the nearest neighbors P1-P8 receive the token to four times as often as the next most nearest neighbors P9-P24.
- the pixels P9, P13, P17 and P21 at the corners of the matrix are not used as contributing pixels or contribute even less frequently.
- pixels in a plus-shaped array contribute, i.e., PI 1, P2, P6, P19 and P22, P8, P4, and P15 in the numbering scheme of FIGURE 4.
- only a column, row, or diagonal row of pixels contribute. Narious other arrangements of contributing pixels may be selected as may be appropriate to chose pixels that produce approximately the same amount of output as would be expected from the defective pixel.
- two defective pixels P0 may occur side by side as illustrated in FIGURE 5 or corner to corner.
- the nearest neighbor pixels P1-P10 surrounding the pair are selected as the contributing pixels.
- the data is processed substantially the same as in FIGURE 3, except that there are two tokens.
- One token corresponds to each of the two defective pixels. Wlienever an input is received from a contributing pixel corresponding to the table location that holds the token for one of the pixels, an event is generated for that pixel and the token is passed.
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- Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- High Energy & Nuclear Physics (AREA)
- Molecular Biology (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Nuclear Medicine (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2006500271A JP4486081B2 (en) | 2003-01-06 | 2004-01-05 | Method and apparatus for recovering dead pixels in a digital imaging system |
US10/541,562 US7453066B2 (en) | 2001-01-06 | 2004-01-05 | Method and apparatus to recover a dead pixel in digital imaging systems |
EP04700142A EP1581823A1 (en) | 2003-01-06 | 2004-01-05 | Method and apparatus to recover a dead pixel in digital imaging systems |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US43822103P | 2003-01-06 | 2003-01-06 | |
US60/438,221 | 2003-01-06 |
Publications (1)
Publication Number | Publication Date |
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WO2004061480A1 true WO2004061480A1 (en) | 2004-07-22 |
Family
ID=32713299
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB2004/000011 WO2004061480A1 (en) | 2001-01-06 | 2004-01-05 | Method and apparatus to recover a dead pixel in digital imaging systems |
Country Status (3)
Country | Link |
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EP (1) | EP1581823A1 (en) |
JP (1) | JP4486081B2 (en) |
WO (1) | WO2004061480A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006304839A (en) * | 2005-04-26 | 2006-11-09 | Shimadzu Corp | Optical or radiation imaging apparatus |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5657400A (en) | 1995-01-31 | 1997-08-12 | General Electric Company | Automatic identification and correction of bad pixels in a large area solid state x-ray detector |
US6118846A (en) | 1999-02-23 | 2000-09-12 | Direct Radiography Corp. | Bad pixel column processing in a radiation detection panel |
US6296387B1 (en) | 1998-11-30 | 2001-10-02 | Commissariat A L'energie Atomique | Method for correcting image defects from a matrix-type X or γ-ray detector |
JP2002330341A (en) | 2001-05-01 | 2002-11-15 | Canon Inc | Radiation image processing unit, image processing system, radiation image processing method, recording medium, and program |
-
2004
- 2004-01-05 EP EP04700142A patent/EP1581823A1/en not_active Withdrawn
- 2004-01-05 WO PCT/IB2004/000011 patent/WO2004061480A1/en active Application Filing
- 2004-01-05 JP JP2006500271A patent/JP4486081B2/en not_active Expired - Fee Related
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5657400A (en) | 1995-01-31 | 1997-08-12 | General Electric Company | Automatic identification and correction of bad pixels in a large area solid state x-ray detector |
US6296387B1 (en) | 1998-11-30 | 2001-10-02 | Commissariat A L'energie Atomique | Method for correcting image defects from a matrix-type X or γ-ray detector |
US6118846A (en) | 1999-02-23 | 2000-09-12 | Direct Radiography Corp. | Bad pixel column processing in a radiation detection panel |
JP2002330341A (en) | 2001-05-01 | 2002-11-15 | Canon Inc | Radiation image processing unit, image processing system, radiation image processing method, recording medium, and program |
Non-Patent Citations (3)
Title |
---|
KEREN I. ET AL.: "A self-correcting active pixel camera", IEEE CONFERENCE PROCEEDINGS ARTICLE, 25 October 2000 (2000-10-25), pages 56 - 64 |
KOREN I ET AL: "A self-correcting active pixel camera", CONFERENCE PROCEEDINGS ARTICLE, 25 October 2000 (2000-10-25), pages 56 - 64, XP010525394 * |
PATENT ABSTRACTS OF JAPAN vol. 2003, no. 03 5 May 2003 (2003-05-05) * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006304839A (en) * | 2005-04-26 | 2006-11-09 | Shimadzu Corp | Optical or radiation imaging apparatus |
JP4617987B2 (en) * | 2005-04-26 | 2011-01-26 | 株式会社島津製作所 | Light or radiation imaging device |
Also Published As
Publication number | Publication date |
---|---|
JP2006515675A (en) | 2006-06-01 |
EP1581823A1 (en) | 2005-10-05 |
JP4486081B2 (en) | 2010-06-23 |
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