Method and apparatus for large field of view imaging and detection and compensation of motion artifacts

Patent metadata

Field	Value
Publication number	US-2016005194-A1
Application number	US-201514856713-A
Country	US
Kind code	A1
Filing date	Sep 17, 2015
Priority date	Jan 21, 2009
Publication date	Jan 7, 2016
Grant date	—

Abstract

A method and apparatus are provided to improve large field of view CT image acquisition by using at least two scanning procedures: (i) one with the radiation source and detector centered and (ii) one in an offset configuration. The imaging data obtained from both of the scanning procedures is used in the reconstruction of the image. In addition, a method and apparatus are provided for detecting motion in a reconstructed image by generating a motion map that is indicative of the regions of the reconstructed image that are affected by motion artifacts. Optionally, the motion map may be used for motion estimation and/or motion compensation to prevent or diminish motion artifacts in the resulting reconstructed image. An optional method for generating a refined motion map is also provided.

First claim

Having thus described the preferred embodiments, the invention is now claimed to be:

1 . An apparatus for generating a motion map, the apparatus comprising:
a radiation source; a radiation sensitive detector which detects radiation emitted by the source that has traversed an examination region; and a reconstructor and an image processor; wherein the radiation source and the radiation sensitive detector are used to acquire projection data at a plurality of angular positions relative to an object disposed in the examination region; wherein the reconstructor is used to generate a reference image from the projection data; wherein reference projection data is obtained from a forward projection of the reference image; wherein differences between the acquired projection data and the reference projection data are computed to determine line integral differences; and wherein the image processor uses the line integral differences to generate a motion map indicative of the regions of a corresponding image reconstructed from the projection data that are affected by motion.

2 . The apparatus of claim 1 , wherein the image processor applies a windowing process to refine the motion map.

3 . The apparatus of claim 1 , wherein the image processor applies a normalization process to refine the motion map.

4 . The apparatus of claim 1 , wherein the image processor applies a volumetric median filter to refine the motion map.

5 . The apparatus of claim 1 , wherein the image processor applies a Gaussian blur to refine the motion map.

6 . The apparatus of claim 1 , wherein the apparatus is a cone-beam computed tomography imaging device.

7 . The apparatus of claim 1 , wherein the image processor processes the volumetric data for display on a user interface.

8 . The apparatus of claim 1 , wherein the motion map indicates the amount of motion correction to be applied to an image.

9 . The apparatus of claim 8 , wherein the image processor uses the motion map in a motion-compensated image reconstruction.

10 . The apparatus of claim 9 , wherein the image processor performs a reconstruction as a weighted average between a motion corrected reconstruction and a reconstruction not corrected for motion, wherein the weights are provided by the motion map.

11 . The apparatus of claim 8 , wherein the motion displacement in a motion-corrected reconstruction is adapted according to the motion map.

12 . A method for generating a motion map, the method comprising the steps of:
acquiring projection data at a plurality of angular positions relative to an object disposed in an examination region; reconstructing from the projection data to generate a reference image; obtaining reference projection data from a forward projection of the reference image; computing differences between the acquired projection data and the reference projection data to determine line integral differences; and using the line integral differences to generate a motion map indicative of the regions of a corresponding image reconstructed from the projection data that are affected by motion.

13 . The method of claim 12 , further comprising the step of applying a windowing process to refine the motion map.

14 . The method of claim 12 , further comprising the steps of refining the motion map by normalizing the motion map, applying a volumetric median filter to the motion map, and applying a Gaussian blur to the motion map.

15 . The method of claim 12 , further comprising the step of using the motion map in conjunction with the corresponding image reconstructed from the projection data to detect regions of the reconstructed image that are affected by motion.

16 . The method of claim 12 , further comprising the step of using the motion map in conjunction with a motion correction technique to compensate for the effects of motion in the corresponding image reconstructed from the projection data.

17 . The method of claim 16 , further comprising compensating for motion only in regions of the corresponding image that are indicated to have been affected by motion by the motion map.

18 . The method of claim 16 , further comprising compensating for motion by applying a weighted value of motion correction to regions of the corresponding image reconstructed from the tomographic projection data, the weighted value being calculated for each region based upon a quantitative amount of motion indicated for each image region by the motion map.

19 . The method of claim 12 , wherein acquiring projection data comprises acquiring projection data during at least two scanning procedures including centered geometry projection data during a centered geometry scanning procedure and offset geometry projection data during an offset geometry scanning procedure, wherein the centered geometry projection data and the offset geometry projection data include an overlap region from opposite views of the object, and wherein reconstructing comprises reconstructing the projection data acquired during the at least two scanning procedures together to generate volumetric data indicative of the object, wherein the centered geometry projection data and the offset geometry projection data are registered based on the overlap region.

Assignees

• Koninkl Philips Nv

Inventors

• Schretter Colas
• Bertram Matthias
• Neukirchen Christoph

Classifications

• A61B6/4452

  the source unit and the detector unit being able to move relative to each other · CPC title

• A61B6/587

  Alignment of source unit to detector unit · CPC title

• G16H50/30

  for calculating health indices; for individual health risk assessment · CPC title

• G06T7/20

  Analysis of motion (motion estimation for coding, decoding, compressing or decompressing digital video signals H04N19/43, H04N19/51) · CPC title

• G06T2207/20032

  Median filtering · CPC title