Cone-beam computed tomography with continuous kV beam acquisition

Patent metadata

Field	Value
Publication number	US-11298088-B2
Application number	US-202016835648-A
Country	US
Kind code	B2
Filing date	Mar 31, 2020
Priority date	Mar 31, 2020
Publication date	Apr 12, 2022
Grant date	Apr 12, 2022

Abstract

A cone-beam computed tomography (CBCT) method uses a continuous beam and an area detector to carry out fast acquisition of projection data. The acquired projection data are then reconstructed to generate tomographic images. In acquisition of the projection data, a radiation source continuously irradiates a subject with a cone beam of radiation from a plurality of angles and an area detector continuously reads out data. A CBCT system including a source operable to produce a cone beam of radiation and an area detector movable in synchrony with the source to rapidly acquire projection data for CBCT construction is also disclosed.

First claim

What is claimed is:

1. A method, comprising:
acquiring a plurality of projections of data set of at least a portion of a subject using a source of radiation and an area detector movable in synchrony with the source, wherein in the acquiring of the plurality of projections of data set, the source continuously irradiates the portion of the subject with a cone beam of radiation from a plurality of angles and the area detector reads out data during the continuous irradiating of the portion of the subject with the cone beam of radiation; and
reconstructing a tomographic image of the portion of the subject based on at least a portion of the plurality of projections of data set,
the method further comprising pre-processing the plurality of projections of data set, wherein the pre-processing comprises weighting data of a given projection acquired in a given time period with data of a projection acquired after the given projection.

2. The method of claim 1 , wherein in the acquiring of the plurality of projections of data set, the source is operated at a kilovoltage (kV) level.

3. The method of claim 1 , wherein the plurality of projections of data set are acquired while the source rotates around the subject in 360 degrees or more and continuously irradiates the portion of the subject during the rotation.

4. The method of claim 1 , wherein the source comprises a focal spot and produces the cone beam of radiation having a cone angle, and the area detector comprises an active detection surface spaced apart from the focal spot of the source at a distance, thereby a rotation of the source and the area detector in synchrony provides a reconstruction volume encompassing the portion of the subject, the reconstruction volume having a field of view ranging from 25 to 50 centimeters and/or a scan length ranging from 15 to 28 centimeters.

5. The method of claim 1 , wherein the area detector comprises a flat-panel imager comprising a plurality of detector pixels in rows and columns each having an addressable photosensitive element and a switching TFT or CMOS transistor.

6. The method of claim 5 , wherein the flat-panel imager comprises an active detection area of about 40×40 cm 2 or larger.

7. The method of claim 1 , wherein the pre-processing further comprising weighting data of the given projection with data of a projection acquired before the given projection.

8. The method of claim 7 , wherein the weighting of data of the given projection comprises giving a weight to a data value of a pixel of a given row (y) based on a time delay in reading out data of the given row (y) relative to a reference row (y0) of the area detector.

9. The method of claim 8 , wherein the weighting of data of the given projection is carried out according to the following linear interpolation:
replace p i ( . . . ,y) by:
w*p i ( . . . , y )+(1− w )* p i+1 ( . . . , y ), where

p i ( . . . ,y) represents a data value of a pixel at row y of a given projection i acquired by the area detector comprising h rows of pixels and y<h/2,
p i+1 ( . . . ,y) represents a data value of the pixel at row y of projection i+1,
w represents a weighting factor, and w=1−(h/2−y)*(lineTime/cycleTime), lineTime represents a time period elapsing between readout of successive rows, and
cycleTime represents a time period elapsing between readout of successive projections,
or
replace p i ( . . . ,y) by:
w*p i ( . . . , y )+(1− w )* p i−1 ( . . . , y ), where

p i ( . . . ,y) represents a data value of a pixel at row y of a given projection i acquired by the area detector comprising h rows of pixels and y>h/2,
p i−1 ( . . . ,y) represents a data value of the pixel at row y of projection i−1,
w represents a weighting factor, and w=1−(y−h/2)*(lineTime/cycleTime) lineTime represents a time period elapsing between readout of successive rows, and
cycle Time represents a time period elapsing between readout of successive projections.

10. A system, comprising:
a source operable to produce a cone beam of radiation, the source being movable relative to a subject to irradiate at least a portion of the subject from a plurality of angles;
an area detector movable in synchrony with the source, the area detector being operable to acquire a plurality of projections of the portion of the subject while the source continuously irradiates the portion of the subject with the cone beam of radiation from the plurality of angles; and
an image processing device configured to reconstruct a tomographic image of the portion of the subject based on at least a portion of the plurality of projections of data set, the image processing device is further configured to pre-process the plurality of projections of data set by weighting data of a given projection acquired in a given time period with data of a projection acquired after the given projection.

11. The system of claim 10 , wherein the source comprises an x-ray tube operable at a kilovoltage level to produce the cone beam of radiation.

12. The system of claim 10 , further comprising a source operable at a megavoltage (MV) level to produce a beam of radiation suitable for treatment of a disease.

13. The system of claim 10 , wherein the area detector comprises a flat-panel imager comprising a plurality of detector pixels in rows and columns each having an addressable photosensitive element and a switching TFT or CMOS transistor.

14. The system of claim 13 , wherein the flat-panel imager comprises an active detection area of about 40×40 cm 2 or larger.

15. The system of claim 10 , wherein the source comprises a focal spot and produces the cone beam of radiation having a cone angle, and the area detector comprises an active detection surface spaced apart from the focal spot of the source at a distance, thereby a rotation of the source and the area detector in synchrony provides a reconstruction volume encompassing the portion of the subject, the reconstruction volume having a field of view ranging from 25 to 50 centimeters and/or a field of height ranging from 15 to 28 centimeters.

16. The system of claim 10 , wherein the image processing device is further configured to pre-process the plurality of projections by weighting data of the given projection acquired in the given time period with data of a projection acquired before the given projection.

17. The method of claim 16 , wherein the weighting of data of the given projection comprises giving a weight to a data value of a pixel of a given row (y) based on a time delay in reading out data of the given row (y) relative to a reference row (y0) of the area detector.

18. The system of claim 17 , wherein the image processing device is configured to weight data of the given projection according to the following linear interpolation:
replace p i ( . . . ,y) by:
w*p i ( . . . , y )+(1− w )* p i+1 ( . . . , y ), where

p i ( . . . ,y) represents a data value of a pixel at row y of a given projection i acquired by the area detector comprising h rows of pixels and y<h/2,
p i+1 ( . . . ,y) represents a data value of the pixel at row y of projection i+1,
w represents a weighting factor, and w=1−(h/2−y)*(lineTime/cycleTime),
lineTime represents a time period elapsing between readout of successive rows, and
cycle Time represents a time period elapsing between readout of successive projections,
or
replace p i ( . . . ,y) by:
w*p i ( . . . , y )+(1− w )* p i−1 ( . . . , y ), where

p i ( . . . ,y) represents a data value of a pixel at row y of a given projection i acquired by the area detector comprising

Assignees

• Varian Medical Systems Int Ag

Inventors

• Lehmann Mathias
• Ansorge Reto
• Waser Manuel
• Morf Daniel

Classifications

• G06T12/20

  Inverse problem, i.e. transformations from projection space into object space · CPC title

• G06T12/10

  Image preprocessing, e.g. calibration, positioning of sources or scatter correction · CPC title

• A61B6/4085

  Cone-beams · CPC title

• A61B6/42

  Arrangements for detecting radiation specially adapted for radiation diagnosis · CPC title

• A61N5/1049

  for verifying the position of the patient with respect to the radiation beam · CPC title