Projection data correction method and apparatus, and radiation tomographic imaging method and apparatus

• US 6,373,919 B1
• Filed: 06/12/2000
• Issued: 04/16/2002
• Est. Priority Date: 08/10/1999
• Status: Expired due to Term

• Current Assignee: GE Healthcare Japan Corporation (Danaher Corporation)
• Original Assignee: GE Yokogawa Medical Systems Limited (GE Aerospace)
• Inventors: Horiuchi, Tetsuya
• Primary Examiner(s): BRUCE, DAVID VERNON
• Application Number:
  US09/592,972
• Time in Patent Office: 673 Days
• Field of Search: 378/4, 378/62, 378/98, 378/901
• US Class Current: 378/62
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

In order to provide a projection data correction method and apparatus that prevents artifact generation in the direction which provides a low count of penetrating radiation, and a radiation tomographic imaging method employing such a projection data correction method and a radiation tomographic imaging apparatus comprising the projection data correction apparatus, projection data Proj_ij is individually corrected by a weighted addition (604, 606, 608) with an average value (602) containing the proximate data. The weight SG_ij of the projection data is decreased as the count of the penetrating radiation from which the projection data is derived becomes smaller.

Claims

1. A projection data correction method comprising the steps of:

individually calculating an average value of data and its proximate data, said data constituting a projection of an object to be imaged by penetrating radiation;

calculating a first product by multiplying said data by a first weighting factor that corresponds to a count of the penetrating radiation from which said data is derived;

calculating a second product by multiplying said average value by a second weighting factor that is a complement of said first weighting factor with respect to one; and

adding said first and second products.

3. A projection data correction method as defined in claim 1 or 2, wherein said first weighting factor is given by the following equation:

2. A projection data correction method comprising the steps of:

individually calculating an average value of data and its proximate data, said data constituting a projection of an object to be imaged by penetrating radiation;

calculating a first product by multiplying said data by a first weighting factor that is approximately proportional to a count of the penetrating radiation from which said data is derived in a range below a predetermined value of the count;

calculating a second product by multiplying said average value by a second weighting factor that is a complement of said first weighting factor with respect to one; and

adding said first and second products.

4. A projection data correction apparatus comprising:

average value calculating means for individually calculating an average value of data and its proximate data, said data constituting a projection of an object to be imaged by penetrating radiation;

first product calculating means for calculating a first product by multiplying said data by a first weighting factor that corresponds to a count of the penetrating radiation from which said data is derived;

second product calculating means for calculating a second product by multiplying said average value by a second weighting factor that is a complement of said first weighting factor with respect to one; and

adder means for adding said first and second products.

6. A projection data correction apparatus as defined in claim 4 or 5, wherein said first weighting factor is given by the following equation:

5. A projection data correction apparatus comprising:

average value calculating means for individually calculating an average value of data and its proximate data, said data constituting a projection of an object to be imaged by penetrating radiation;

first product calculating means for calculating a first product by multiplying said data by a first weighting factor that is approximately proportional to a count of the penetrating radiation from which said data is derived in a range below a predetermined value of the count;

second product calculating means for calculating a second product by multiplying said average value by a second weighting factor that is a complement of said first weighting factor with respect to one; and

adder means for adding said first and second products.

7. A radiation tomographic imaging method for emitting radiation toward an object to be imaged in a plurality of view directions and detecting penetrating radiation, and producing an image using a projection based on signals detected by said step of emitting/detecting radiation, wherein said step of producing an image is performed by:

individually calculating an average value of data and its proximate data, said data constituting said projection;

calculating a first product by multiplying said data by a first weighting factor that corresponds to a count of the penetrating radiation from which said data is derived;

calculating a second product by multiplying said average value by a second weighting factor that is a complement of said first weighting factor with respect to one;

adding said first and second products; and

reconstructing an image using a projection comprised of data resulted from said addition.

8. A radiation tomographic imaging method as defined in claim 7, wherein an X-ray is employed as said radiation.

9. A radiation tomographic imaging method for emitting radiation toward an object to be imaged in a plurality of view directions and detecting penetrating radiation, and producing an image using a projection based on signals detected by said step of emitting/detecting radiation, wherein said step of producing an image is performed by:

individually calculating an average value of data and its proximate data, said data constituting said projection;

calculating a first product by multiplying said data by a first weighting factor that is approximately proportional to a count of penetrating radiation from which said data is derived in a range below a predetermined value of the count;

calculating a second product by multiplying said average value by a second weighting factor that is a complement of said first weighting factor with respect to one;

adding said first and second products; and

reconstructing an image using a projection comprised of data resulted from said addition.

10. A radiation tomographic imaging method as defined in claim 9, wherein an X-ray is employed as said radiation.

11. A radiation tomographic imaging method as defined in claim 7, 8, 9 or 10, wherein said first weighting factor is given by the following equation:

12. A radiation tomographic imaging apparatus comprising:

radiation emitting/detecting means for emitting radiation toward an object to be imaged in a plurality of view directions and detecting penetrating radiation, and

image producing means for producing an image using a projection based on signals detected by said radiation emitting/detecting means, wherein said image producing means comprises;

average value calculating means for individually calculating an average value of data and its proximate data, said data constituting said projection;

first product calculating means for calculating a first product by multiplying said data by a first weighting factor that corresponds to a count of the penetrating radiation from which said data is derived;

second product calculating means for calculating a second product by multiplying said average value by a second weighting factor that is a complement of said first weighting factor with respect to one;

adder means for adding said first and second products; and

image reconstruction means for reconstructing an image using a projection comprised of data resulted from said addition.

13. A radiation tomographic imaging apparatus as defined in claim 12, wherein an X-ray is employed as said radiation.

16. A radiation tomographic imaging apparatus as defined in claim 12, 13, 14 or 15, wherein said first weighting factor is given by the following equation:

14. A radiation tomographic imaging apparatus comprising:

radiation emitting/detecting means for emitting radiation toward an object to be imaged in a plurality of view directions and detecting penetrating radiation, and

image producing means for producing an image using a projection based on signals detected by said radiation emitting/detecting means, wherein said image producing means comprises;

average value calculating means for individually calculating an average value of data and its proximate data, said data constituting said projection;

first product calculating means for calculating a first product by multiplying said data by a first weighting factor that is approximately proportional to a count of the penetrating radiation from which said data is derived in a range below a predetermined value of the count;

second product calculating means for calculating a second product by multiplying said average value by a second weighting factor that is a complement of said first weighting factor with respect to one;

adder means for adding said first and second products; and

image reconstruction means for reconstructing an image using a projection comprised of data resulted from said addition.

15. A radiation tomographic imaging apparatus as defined in claim 14, wherein an X-ray is employed as said radiation.