Method and apparatus for generating three-dimensional, multiply resolved volume images of an examination subject

• US 7,020,319 B2
• Filed: 10/11/2002
• Issued: 03/28/2006
• Est. Priority Date: 10/11/2001
• Status: Active Grant

• Current Assignee: Siemens Healthineers AG (Siemens AG)
• Original Assignee: Siemens AG
• Inventors: Mertelmeier, Thomas, Strobel, Norbert
• Primary Examiner(s): Wu, Jingge
• Assistant Examiner(s): Tabatabai, Abolfazl
• Application Number:
  US10/269,686
• Publication Number:
  US 20030081821A1
• Time in Patent Office: 1,264 Days
• Field of Search: 382128-134, 378/4, 378/17, 378/98.4, 378/98.6, 378/98.9, 378/101, 378/163, 378/901, 128/916, 128/920, 600/444, 250/363.03, 250/363.04, 250/369, 250/371, 250/375, 250/559.19, 250/559.21, 250/577
• US Class Current: 382/132
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4085 Cone-beams
• CPC Class Codes: A61B 6/5235 combining images from the same or different ionising radiation imaging techniques, e.g. PET and CT
• CPC Class Codes: G06T 11/005 Specific pre-processing for tomographic reconstruction, e.g. calibration, source positioning, rebinning, scatter correction, retrospective gating
• CPC Class Codes: G06T 3/4084 in the transform domain, e.g. fast Fourier transform [FFT] domain scaling
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: Y10S 378/901 Computer tomography program or processor

Abstract

In a method and examination apparatus for generating three-dimensional, multiply resolved volume images of an examination subject on the basis of two-dimensional projection images that can be registered with the apparatus, as radiation images obtained with a radiation source and a radiation receiver in an exposure procedure of the examination subject, a set of two-dimensional projection images is registered, one part of the set being registered with low resolution and one part of the set being registered with high resolution, transforming the high-resolution projection images are transformed so as to have the same scale, the same sampling rate and the same resolution as the low-resolution projection images (downscaling), and a three-dimensional volume image with low resolution is generated on the basis of the low-resolution projection images as well as the transformed projection images and a high-resolution volume image is generated on the basis of the high-resolution projection images.

Claims

1. A method for generating three-dimensional, multiply resolved volume images of an examination subject, comprising the steps of:

in an exposure procedure, irradiating an examination subject with X-rays from a radiation source and detecting X-rays attenuated by the subject with a radiation receiver and thereby registering a plurality of low-resolution two-dimensional projection images and a plurality of high-resolution two-dimensional projection images, said low resolution projection images and said high-resolution projection images each having a scale and a sampling rate associated therewith;

transforming said high-resolution projection images, and still retaining said high-resolution projection images, to produce transformed projection images having a scale and a sampling rate which are the same as the scale and the sampling rate of said low-resolution projection images; and

generating a three-dimensional volume image having a low resolution from said low-resolution projection images and said transformed projection images, and generating a three-dimensional volume image with high resolution from said high-resolution projection images.

2. A method as claimed in claim 1 wherein said radiation detector contains a plurality of pixels, and comprising generating said low-resolution projection images by interconnecting selected juxtaposed pixels in said plurality of pixels.

3. A method as claimed in claim 1 comprising registering said low-resolution projection images and said high-resolution projection images in a predetermined, alternating sequence.

4. A method as claimed in claim 3 comprising registering a total of N projection images, with every n^th projection image being registered with high resolution.

5. A method as claimed in claim 1 comprising reconstructing the respective three-dimensional volume images using a conical beam reconstruction method.

6. A method as claimed in claim 5 comprising reconstructing the respective three-dimensional volume images in a conical beam reconstruction method with filtered back-projection.

7. A method as claimed in claim 6 comprising employing a filter which promotes contrast resolution in the filtered back-projection for generating said three-dimensional volume image with low resolution.

8. A method as claimed in claim 6 comprising employing a filter which promotes spatial resolution in said filtered back-projection.

9. A method as claimed in claim 1 comprising the additional step of presenting said respective three-dimensional volume images on a display monitor in a presentation mode selected from the group consisting of individual presentation of the respective three-dimensional volume images and overlaid presentation of the three-dimensional volume images.

10. A method for generating three-dimensional, multiply resolved volume images of an examination subject, comprising the steps of:

in an examination procedure, irradiating an examination subject with x-rays from a radiation source and detecting x-rays attenuated by said subject with a radiation detector having a high-resolution detection region and a low-resolution detection region, and thereby obtaining a plurality of two-dimensional projection images each having a high resolution portion obtained from said high-resolution region of said radiation receiver and a low-resolution portion obtained from said low-resolution region of said radiation receiver, and in each of said projection images, said high-resolution portion and said low-resolution portion each having a sampling rate associated therewith;

interpolating the low-resolution portion of each projection image to adapt the sampling rate thereof so that the sampling rate of said low-resolution portion is equal to the sampling rate of the high-resolution portion; and

executing a filtered back-projection of said plurality of projection images with a uniform sampling rate and thereby generating a three-dimensional volume image having a volume portion with high resolution and a volume portion with low resolution.

11. A method as claimed in claim 10 wherein said radiation receiver contains a plurality of pixels and comprising obtaining the respective low-resolution portions of said projection images by interconnecting selected juxtaposed pixels in said low-resolution region of said radiation detector.

12. A method as claimed in claim 10 wherein the step of interpolating the low-resolution portion in each of said projection images comprises:

filtering the high-resolution portion of said projection image separately with a low-pass filter and a high-pass filter in a two-dimensional wavelet transformation, thereby obtaining a band matrix containing four sub-bands, one of said sub-bands containing only a low-pass filtered portion of the projection image comprised of approximation coefficients, and the others of said sub-bands respectively containing different high-pass portions of said projection image comprising detail coefficients;

integrating the sub-band comprising approximation coefficients in each of said projection images, instead of integrating the high-resolution portion of that projection image, to obtain an integration image with a lower resolution;

employing said integration image as a low-pass sub-band in a second band matrix, also having a total of four sub-bands;

filling the other sub-bands of said second band matrix with said detailed coefficients of said sub-bands of said first band matrix at positions in said second band matrix respectively corresponding with positions in said first band matrix, and with filler coefficients at all other positions in said second band matrix; and

subjecting said second band matrix to an inverse wavelet transformation.

13. A method as claimed in claim 12 wherein the step of filling all other positions in said second band matrix with filler coefficients comprises filling all other positions in said second band matrix with filler coefficients having a value of zero.

14. A method as claimed in claim 12 comprising repeating the steps of filtering said high-resolution region, integrating said sub-band, employing said integration image as a low-pass sub-band, filling said second band matrix, and subjecting said second band matrix to an inverse wavelet transformation, until said sampling rate of said low-resolution portion equals the sampling rate of said high-resolution portion.

15. A method as claimed in claim 10 comprising employing a radiation detector having a variable high-resolution region as said radiation detector.

16. An apparatus for generating three-dimensional, multiply resolved volume images of an examination subject, comprising:

an x-ray source and a radiation receiver for, in an exposure procedure, irradiating an examination subject with X-rays from said radiation source and detecting X-rays attenuated by the subject with said radiation receiver and thereby registering a plurality of low-resolution two-dimensional projection images and a plurality of high-resolution two-dimensional projection images, said low resolution projection images and said high-resolution projection images each having a scale and a sampling rate associated therewith;

an image-processing unit for transforming said high-resolution projection images, and still retaining said high-resolution projection images, to produce transformed projection images having a scale and a sampling rate which are the same as the scale and the sampling rate of said low-resolution projection images; and

said image-processing unit generating a three-dimensional volume image having a low resolution from said low-resolution projection images and said transformed projection images, and generating a three-dimensional volume image with high resolution from said high-resolution projection images.

17. An apparatus for generating three-dimensional, multiply resolved volume images of an examination subject, comprising the steps of:

an x-ray source and a radiation receiver having a high-resolution detection region and a low-resolution detection region for, in an examination procedure, irradiating an examination subject with x-rays from said radiation source and detecting x-rays attenuated by said subject with said radiation detector, and thereby obtaining a plurality of two-dimensional projection images each having a high resolution portion obtained from said high-resolution region of said radiation receiver and a low-resolution portion obtained from said low-resolution region of said radiation receiver, and in each of said projection images, said high-resolution portion and said low-resolution portion each having a sampling rate associated therewith;

an image-processing unit for interpolating the low-resolution portion of each projection image to adapt the sampling rate thereof so that the sampling rate of said low-resolution portion is equal to the sampling rate of the high-resolution portion; and

said image-processing unit executing a filtered back-projection of said plurality of projection images with a uniform sampling rate and thereby generating a three-dimensional volume image having a volume portion with high resolution and a volume portion with low resolution.