Method of calibration of a stereoscopic camera system for use with a radio therapy treatment apparatus

Patent metadata

Field	Value
Publication number	US-10456601-B2
Application number	US-201815946362-A
Country	US
Kind code	B2
Filing date	Apr 5, 2018
Priority date	Jul 17, 2013
Publication date	Oct 29, 2019
Grant date	Oct 29, 2019

Abstract

The disclosed calibration method includes a calibration phantom positioned on an adjustable table on the surface of a mechanical couch, with the phantom's center at an estimated location for the iso-center of a radio therapy treatment apparatus. The calibration phantom is then irradiated using the apparatus, and the relative location of the center of the calibration phantom and the iso-center of the apparatus is determined by analyzing images of the irradiation of the calibration phantom. The calibration phantom is then repositioned by the mechanical couch applying an offset corresponding to the determined relative location of the center of the calibration phantom and the iso-center of the apparatus to the calibration phantom. Images of the relocated calibration phantom are obtained, to which the offset has been applied, and the obtained images are processed to set the co-ordinate system of a stereoscopic camera system relative to the iso-center of the apparatus.

First claim

What is claimed is:

1. A method of calibrating a 3D camera. system for use with a radio therapy treatment apparatus, the method comprising:
i) storing a reference 3D computer model of a reference surface of a reference calibration phantom, the reference calibration phantom being configured with a known surface, a known position, and a known orientation to a co-ordinate system of the camera system;
ii) positioning a physical calibration phantom in the radio therapy treatment apparatus, the physical calibration phantom having an iso-center which defines an original of the radio therapy treatment apparatus co-ordinate system;
iii) utilizing a 3D camera system to obtain images of the physical calibration phantom;
iv) irradiating the positioned physical calibration phantom using the radio therapy treatment apparatus to obtain irradiation images of the positioned physical calibration phantom;
v) determining a first transformation required to transform the position and orientation of the positioned physical calibration phantom into the co-ordinate system of the radio therapy treatment apparatus, by analyzing the images obtained in step iv);
vi) processing the images obtained by the 3D camera system in step iii) to generate a 3D computer model of a surface of the positioned physical calibration phantom;
vii) determining a second transformation required to transform the generated 3D computer model of the surface of the positioned physical calibration phantom into alignment with the reference surface of the reference calibration phantom; and
viii) applying the first and second transformations to transform generated 3D models obtained by the 3D camera system into corresponding positions and orientations in the co-ordinate system of the therapy treatment apparatus.

2. The method of claim 1 , wherein the physical calibration phantom comprises a calibration cube and the stored reference 3D computer model is configured as a 3D computer model of said reference surface of said calibration cube.

3. The method of claim 1 , wherein the physical calibration phantom comprises an acrylic or polystyrene cube.

4. The method of claim 1 , wherein the physical calibration phantom contains an arrangement of one or more targets made of a material having good radiation stability.

5. The method of claim 4 wherein the targets comprise one or more metallic or ceramic balls.

6. The method of claim 5 wherein the targets arranged asymmetrically within the calibration phantom.

7. The method according to claim 1 , wherein said physical calibration phantom is configured with a known asymmetrical arrangement of targets provided in a fixed orientation within the body of the physical calibration phantom, so as to enable the orientation of said physical calibration phantom to be determined from said irradiation images, enabling the orientation of the physical phantom to be determined with respect to the treatment co-ordinate system.

8. The method according to claim 2 , wherein said physical calibration phantom is configured with a known asymmetrical arrangement of targets provided in a fixed orientation within the body of the physical calibration phantom, so as to enable the orientation of said physical calibration phantom to be determined from said irradiation images, enabling the orientation of the physical phantom to be determined with respect to the treatment co-ordinate system.

9. The method according to claim 3 , wherein said physical calibration phantom is configured with a known asymmetrical arrangement of targets provided in a fixed orientation within the body of the physical calibration phantom, so as to enable the orientation of said physical calibration phantom to be determined from said irradiation images, enabling the orientation of the physical phantom to be determined with respect to the treatment co-ordinate system.

Assignees

• Vision Rt Ltd

Inventors

• Meir Ivan
• Allen Martin
• Hale Gideon
• Smith Norman
• Howe Robert

Classifications

• A61N2005/1076

  using a dummy object placed in the radiation field, e.g. phantom · CPC title

• A61B6/584

  determining position of components of the apparatus or device using images of the phantom · CPC title

• A61N5/1049 Primary

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

• G06T7/85

  Stereo camera calibration · CPC title

• G06T2207/30004

  Biomedical image processing · CPC title