Radiation detector noise reduction method and radiation detector

• US 6,453,008 B1
• Filed: 07/28/2000
• Issued: 09/17/2002
• Est. Priority Date: 07/29/1999
• Status: Expired due to Term

• Current Assignee: Toshiba Medical Systems Corporation (Canon Inc.)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Sakaguchi, Takuya, Nagai, Seiichiro
• Primary Examiner(s): Bruce, David V.
• Assistant Examiner(s): Hobden, Pamela R.
• Application Number:
  US09/628,282
• Time in Patent Office: 781 Days
• Field of Search: 378/98.7, 378/98.2, 378/207, 250/370.11, 250/370.09
• US Class Current: 378/98.7
• CPC Class Codes: H04N 25/60 Noise processing, e.g. detecting, correcting, reducing or removing noise
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30

Abstract

A radiation detector noise reduction method includes the step of detecting incident radiation with a radiation detecting section, the radiation detecting section having a plurality of pixels arrayed in the form of a matrix, reading out the detection signal from the radiation detecting section through a readouting section, and correcting the readout detection signal with a correction section, wherein the correction step includes the first sub-step of correcting the detection signal on the basis of a first correction value corresponding to noise originating in the radiation detecting section, and the second sub-step of correcting the detection signal on the basis of a second correction value corresponding to noise originating in the readouting section, the second sub-step being executed before the first sub-step.

Claims

1. A radiation detector noise reduction method comprising the steps of:

detecting incident radiation with a radiation detecting section, the radiation detecting section having a plurality of pixels arrayed in matrix;

reading out the detection signal from the radiation detecting section through a readouting section; and

correcting the readout detection signal with a correction section,

wherein the correction step includes the first sub-step of correcting the detection signal on the basis of a first correction value corresponding to noise originating in the radiation detecting section, and the second sub-step of correcting the detection signal on the basis of a second correction value corresponding to noise originating in the readouting section, the second sub-step being executed before the first sub-step.

2. A method according to claim 1, wherein the second correction value corresponds to gain noise in the readouting section.

3. A method according to claim 1, wherein the first correction value corresponds to gain noise in the radiation detecting section and line artifact noise in the radiation detecting section, and the second correction value corresponds to gain noise in the readouting section.

4. A method according to claim 3, further comprising the step of acquiring the readouting section gain noise, the step of acquiring the readouting section gain noise including the sub-step of electrically separating the readouting section from the radiation detecting section, the sub-step of supplying a calibration signal to the readouting section, and the sub-step of obtaining the readouting section gain noise on the basis of an output signal from the readouting section which responds to the supplied calibration signal.

5. A method according to claim 3, further comprising the step of acquiring the detecting section gain noise, the step of acquiring the detecting section gain noise including the sub-step of electrically separating the readouting section from the radiation detecting section, the sub-step of supplying a calibration signal to the detecting section, and the sub-step of obtaining the detecting section gain noise on the basis of an output signal from the readouting section which responds to the supplied calibration signal.

6. A method according to claim 3, wherein information of the readouting section gain noise is measured in advance in an initial stage in manufacturing the readouting section and stored in the correction section.

7. A method according to claim 3, wherein information of the detecting section gain noise is measured in advance in an initial stage in manufacturing the radiation detecting section and stored in the correction section.

8. A method according to claim 3, wherein information of the readouting section gain noise is acquired in a periodic test on the readouting section and stored in the correction section.

9. A method according to claim 3, wherein information of the detecting section gain noise is acquired in a periodic test on the detecting section and stored in the correction section.

10. A radiation detecting section noise reduction method comprising the steps of:

detecting incident radiation with a radiation detecting section, the radiation detecting section having a plurality of pixels arrayed in the form of a matrix;

reading out the detection signal from the radiation detecting section through a readouting section; and

correcting the readout detection signal,

wherein the correction step includes

the first sub-step of subtracting a result obtained by adding offset noise in the readouting section to the product of the detecting section offset noise and the readouting section gain noise from the detection signal,

the second sub-step of multiplying a difference result obtained in the first sub-step by the reciprocal of the readouting section gain noise,

the third sub-step of subtracting line artifact noise in the detecting section from the multiplication result obtained in the second sub-step, and

the fourth sub-step of multiplying the difference result obtained in the third sub-step by the reciprocal of gain noise in the detecting section.

11. A radiation detecting section noise reduction method comprising the steps of:

detecting incident radiation with a radiation detecting section, the radiation detecting section having a plurality of pixels arrayed in the form of a matrix;

reading out the detection signal from the radiation detecting section through a readouting section; and

correcting the readout detection signal,

wherein the correction step includes

the first sub-step of subtracting offset noise in the readouting section from the detection signal,

the second sub-step of multiplying the difference result obtained in the first sub-step by gain noise in the readouting section,

the third sub-step of subtracting offset noise in the detecting section from the multiplication result obtained in the second sub-step,

the fourth sub-step of subtracting line artifact noise in the detecting section from the difference result obtained in the third sub-step, and

the fifth sub-step of multiplying the difference result obtained in the fourth sub-step by gain noise in the detecting section.

12. A radiation detecting section noise reduction method comprising the steps of:

detecting incident radiation with a radiation detecting section, the radiation detecting section having a plurality of pixels arrayed in the form of a matrix;

reading out the detection signal from the radiation detecting section through a readouting section; and

correcting the readout detection signal,

wherein the correction step includes

the first sub-step of subtracting a result obtained by adding offset noise in the readouting section to the product of offset noise in the detecting section and gain noise in the readouting section from the detection signal,

the second sub-step of subtracting a value obtained by multiplying line artifact noise in the detecting section by the gain noise in the readouting section from the difference result obtained in the first sub-step, and

the third sub-step of multiplying the difference result obtained in the second sub-step by the reciprocal of the product of gain noise in the detecting section and the gain noise in the readouting section.

13. A radiation detecting section noise reduction method comprising the steps of:

detecting incident radiation with a radiation detecting section, the radiation detecting section having a plurality of pixels arrayed in the form of a matrix;

reading out the detection signal from the radiation detecting section through a readouting section; and

correcting the readout detection signal,

wherein the correction step includes

the first sub-step of multiplying the detection signal by the reciprocal of the readouting section gain noise,

the second sub-step of subtracting a result obtained by adding the detecting section offset noise and a result obtained by multiplying the detection signal by the reciprocal of the readouting section gain noise from a result obtained in the first sub-step,

the third sub-step of subtracting line artifact noise in the detecting section from the multiplication result obtained in the second sub-step, and

the fourth sub-step of multiplying the difference result obtained in the third sub-step by the reciprocal of gain noise in the detecting section.

15. A detector according to claim 13, wherein said correction section comprises a subtractor for subtracting the correction value which is stored in said storage section and corresponds to the readout scheme from the detection signal.

14. A radiation detector comprising:

a radiation detecting section for detecting incident radiation, said radiation detecting section having a plurality of pixels arrayed in the form of a matrix;

a readouting section for reading out a detection signal detected by said radiation detecting section from said radiation detecting section, said readouting section having a plurality of readout schemes which can be selectively used;

a storage section for storing correction values corresponding to the readout schemes in correspondence with the readout schemes; and

a correction section for correcting the output detection signal on the basis of the correction value selectively read out from said storage section in accordance with the readout scheme.

16. A detector according to claim 14, further comprising a memory controller for storing, in said storage section in correspondence with the respective readout schemes, a value of an output signal from said radiation detecting section when substantially no radiation is incident.

17. A detector according to claim 16, wherein said memory controller starts write operation of said storage section when application of radiation onto said radiation detecting section is stopped, and stops the write operation when radiation is applied onto said radiation detecting section.

18. A detector according to claim 14, wherein

said radiation detecting section comprises a plurality of gate lines, a plurality of signal lines intersecting the gate lines, and a plurality of pixels arranged near a plurality of intersections of the gate lines and the signal lines, each of the pixels including a pair of a photoelectric conversion element and a pixel electrode,

said readouting section comprises a plurality of switching elements arranged between the pixel electrodes and the signal lines, the switching elements having gates to which the gate lines are connected, and a gate line driver for selectively applying a predetermined voltage to the gate line, and

the plurality of readout schemes differ in procedures of driving the gate lines by the gate line driver.

19. A detector according to claim 18, wherein the plurality of readout schemes include a first readout scheme of separately driving the gate lines, a second readout scheme of driving the gate lines in units of predetermined groups, a third readout scheme of driving some of the gate lines by using the first or second readout scheme, and a fourth readout scheme of executing the first to third readout schemes upon shortening a driving time for the gate lines.

20. A detector according to claim 14, wherein the stored correction value is an average of a sum of correction values repeatedly acquired by the same readout scheme.

21. A radiation detector comprising:

a radiation detecting section for detecting incident radiation, said radiation detecting section having a plurality of pixels arrayed in the form of a matrix;

a readouting section for reading out the detection signal from said radiation detecting section; and

a correction section for correcting the readout detection signal,

wherein some of the plurality of pixels are substantially shielded against the radiation, and said correction section corrects signals from the pixels which are not shielded on the basis of signals from the shielded pixels.

22. A detector according to claim 21, wherein said readouting section comprises a plurality of amplifiers for amplifying signals from the pixels, the amplifier corresponding to the shielded pixel having an amplification factor is higher than that of the amplifier corresponding to the pixel which is not shielded.

23. A detector according to claim 22, wherein the amplifiers include capacitors, the capacitor of the amplifier corresponding to the shielded pixel having a capacitance is smaller than that of the amplifier corresponding to the pixel which is not shielded.

24. A detector according to claim 22, further comprising:

a multiplier for multiplying an output signal from the shielded pixel by a ratio of the capacitance of the capacitor of the amplifier corresponding to the pixel which is not shielded to the capacitance of the capacitor of the amplifier corresponding to the shielded pixel; and

a subtractor for subtracting the product from an output signal from the pixel which is not shielded.

25. A radiation detector comprising:

a radiation detecting section for detecting incident radiation, said radiation detecting section having a plurality of pixels arrayed in the form of a matrix;

a readouting section for reading out the detection signal from said radiation detecting section; and

a correction section for correcting the readout detection signal,

wherein first pixels of the plurality of pixels which are located on one end, and second pixels thereof which are located on the other end are substantially shielded against the radiation, and said correction section corrects signals from the pixels which are not shielded on the basis of signals from said first and second pixels.

26. A detector according to claim 25, wherein said correction section corrects signals from the pixels which are not shielded on the basis of distance interpolation values between signals from the first and second pixels.

27. A radiation detector comprising:

a radiation detecting section for detecting incident radiation, said radiation detecting section having a plurality of pixels arrayed in the form of a matrix;

a readouting section for reading out the detection signal from said radiation detecting section; and

a plurality of switching elements for separating said readouting section from said radiation detecting section.

28. A detector according to claim 27, further comprising:

a calibration signal generator for supplying a calibration signal to said readouting section separated from said radiation detecting section by said switching elements;

a calculation section for calculating a correction value on the basis of an output signal from said calibration signal generator which responds to the calibration signal; and

a correction section for correcting a signal read out from said radiation detecting section through said readouting section on the basis of the correction value.

29. A detector according to claim 28, wherein the correction value corresponds to gain noise and/or offset noise in said readouting section.

30. A detector according to claim 29, wherein information of the readouting section gain noise is acquired in an initial manufacturing period for said readouting section, and stored in said correction section.

31. A detector according to claim 29, wherein the information of the readout gain noise is acquired in a periodic test on said readouting section and stored in said correction section.

32. A detector according to claim 29, wherein the information of the readout gain noise is independently obtained as an eigenvalue for each column of pixels.

33. A radiation diagnostic system comprising

a radiation generating unit;

a radiation detector detecting a radiation through a subject from said radiation generating unit;

a display unit displaying an image based on an output of said radiation detector; and

a control unit controlling said radiation generating unit, said radiation detector and said display unit, wherein said radiation detector including;

a radiation detecting section for detecting incident radiation, said radiation detecting section having a plurality of pixels arrayed in the form of a matrix;

a readouting section for reading out a detection signal detected by said radiation detecting section from said radiation detecting section, said readouting section having a plurality of readout schemes which can be selectively used;

a storage section for storing correction values corresponding to the readout schemes in correspondence with the readout schemes; and

a correction section for correcting the output detection signal on the basis of the correction value selectively read out from said storage section in accordance with the readout scheme.

34. A radiation diagnostic system comprising

a radiation generating unit;

a radiation detector detecting a radiation through a subject from said radiation generating unit;

a display unit displaying an image based on an output of said radiation detector; and

a control unit controlling said radiation generating unit, said radiation detector and said display unit, wherein said radiation detector including;

a radiation detecting section for detecting incident radiation, said radiation detecting section having a plurality of pixels arrayed in the form of a matrix;

a readouting section for reading out the detection signal from said radiation detecting section; and

a correction section for correcting the readout detection signal,

wherein some of the plurality of pixels are substantially shielded against the radiation, and said correction section corrects signals from the pixels which are not shielded on the basis of signals from the shielded pixels.

35. A radiation diagnostic system comprising

a radiation generating unit;

a radiation detector detecting a radiation through a subject from said radiation generating unit;

a display unit displaying an image based on an output of said radiation detector; and

a control unit controlling said radiation generating unit, said radiation detector and said display unit, wherein said radiation detector including;

a radiation detecting section for detecting incident radiation, said radiation detecting section having a plurality of pixels arrayed in the form of a matrix;

a readouting section for reading out the detection signal from said radiation detecting section; and

a plurality of switching elements for separating said readouting section from said radiation detecting section.