Modulating gantry rotation speed and image acquisition in respiratory correlated (4D) cone beam CT images

Patent metadata

Field	Value
Publication number	US-9538976-B2
Application number	US-201214131896-A
Country	US
Kind code	B2
Filing date	Jul 27, 2012
Priority date	Jul 28, 2011
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

A method of optimizing 4D cone beam computed tomography (4DCBCT) imaging is provided that includes using a scanner to generate projections of a target, where the projections are used to form a cone beam computed tomography (CBCT) scan of the target, where the CBCT includes a 3D image of the target, and using an appropriately programmed computer to control rotation speed of a gantry and projection acquisition of the CBCT in real-time according to a measured patient respiratory signal, where the real-time acquisition of the 4CBCT forms an optimized 4DCBCT image set.

First claim

What is claimed:

1. A method of optimizing 4D cone beam computed tomography (4DCBCT) imaging, comprising:
a. generating by scanner projections of a target in a single half fan acquisition or a single full fan acquisition using an x-ray source, wherein said single half fan acquisition comprises a single 360-degree gantry rotation, wherein said full fan acquisition comprises a single 180-degree gantry rotation plus a fan angle ω;
b. forming by said scanner a cone beam computed tomography (CBCT) scan of said target from said projections, wherein said CBCT comprises a 3D image of said target; and
c. controlling by an appropriately programmed computer a modulated rotation speed of said gantry and projection acquisition of said CBCT in real-time according to a measured patient respiratory signal using continuous gantry motion and ungated projection acquisition, wherein said ungated projection acquisition comprises segmenting a breathing cycle into distinct fractions of said breathing cycle, wherein each said distinct fraction of said breathing cycle defines a breathing cycle bin location, wherein two degrees of freedom comprise controlling the motion of said gantry and a varied time interval between said ungated projection acquisition, wherein an image is acquired at each said breathing cycle bin location during said single half fan acquisition or said single full fan acquisition, wherein an angle of said gantry is regulated and a rate of a projection pulse from said x-ray source is regulated in response to said respiratory signal, wherein a set of evenly spaced said scanner projections are obtained in a number of phase bins or in a number of displacement bins during said breathing cycle, wherein in each said breathing cycle bin location, an image is reconstructed from said scanner projections to output a 4D view of the anatomy of said patient, wherein the motion of the lungs of said patient and a tumor of said patient are observed during said breathing cycle, wherein said real-time ungated projection acquisition of said CBCT forms an optimized 4DCBCT.

2. The method of optimizing 4DCBCT imaging of claim 1 , wherein a time interval between projections of said CBCT is varied.

3. The method of optimizing 4DCBCT imaging of claim 1 , wherein acceleration and a velocity of said gantry are varied.

4. The method of optimizing 4DCBCT imaging of claim 1 , wherein a breathing trace is used to optimize a projection schedule.

5. The method of optimizing 4DCBCT imaging of claim 1 , wherein said optimized projection schedule comprises regulating a gantry angle and regulating a projection pulse rate.

6. The method of optimizing 4DCBCT imaging of claim 1 , wherein said control of said modulated gantry rotation speed and projection acquisition of said 4DCBCT in real-time comprises:
a. analyzing by sensors a patient's breathing pattern to determine a representative breathing trace;
b. separating the patients representative breathing trace into a number of phase or displacement based respiratory bins;
c. determining and applying by mathematical optimization techniques on said computer a gantry angle and a projection pulse rate schedule from said representative breathing cycle;
d. recomputing by said computer said gantry angle and a projection pulse rate schedule if said patient's breathing deviates from said representative breathing cycle; and
e. continuing said projection acquisition according to said recomputed gantry angle and projection pulse rate schedule.

7. The method of optimizing 4DCBCT imaging of claim 1 , wherein motion of said gantry is regulated within specified limits, wherein said limits are selected from the group consisting of minimum and maximum velocity, minimum and maximum acceleration, minimum and maximum jerk, minimum and maximum time between projections, minimum and maximum number of projections, minimum and maximum number of projections per respiratory bin, maximum imaging radiation dose, minimum and maximum image quality, minimum and maximum probability on the accuracy of the schedule to adhere to an irregular breathing cycle, minimum and maximum likelihood of reconstructing a suitable schedule when a patients breathing becomes irregular, minimum and maximum number of respiratory bins and total imaging time.

8. The method of optimizing 4DCBCT imaging of claim 1 , wherein said patient respiratory signal is used to modulate said modulated speed of said gantry and modulate said projection acquisition to yield images for each phase of a breathing trace at a predetermined and optimized angular spacing.

9. The method of optimizing 4DCBCT imaging of claim 8 , wherein optimizing said gantry angle comprises operations selected from the group consisting of minimizing the time required to acquire the 4DCBCT projections, minimizing the angular separation between the gantry angles for each projection, minimizing the root mean squared of the angular separation between the projections, maximizing the image quality in each respiratory bin, maximizing a number of images acquired, maximizing a number of respiratory bins, maximizing a likelihood of acquiring suitable quality images when a patients breathing becomes irregular, maximizing a robustness of a schedule, and minimizing a radiation dose to said patient.

Assignees

• Keall Paul J
• O'Brien Ricky
• Cooper Benjamin J
• Lu Jun
• Williamson Jeffrey F
• Univ Leland Stanford Junior
• Univ Sydney

Inventors

• Keall Paul J
• O'Brien Ricky
• Cooper Benjamin J
• Lu Jun
• Williamson Jeffrey F

Classifications

• A61B6/541 Primary

  involving acquisition triggered by a physiological signal · CPC title

• A61N2005/1061

  using an x-ray imaging system having a separate imaging source · CPC title

• A61B6/486

  involving generating temporal series of image data · CPC title

• A61B6/5264

  due to motion · CPC title

• A61B6/5205

  involving processing of raw data to produce diagnostic data · CPC title