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

Patent metadata

Field	Value
Publication number	US-2016129283-A1
Application number	US-201414899112-A
Country	US
Kind code	A1
Filing date	Jul 11, 2014
Priority date	Jul 17, 2013
Publication date	May 12, 2016
Grant date	—

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 centre at an estimated location for the iso-centre 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-centre 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 centre of the calibration phantom and the iso-centre 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-centre of the apparatus.

First claim

1 . A method of calibrating a stereoscopic camera system for use with a radio therapy treatment apparatus, the method comprising:
positioning a calibration phantom with the phantom's centre at an estimated location for the iso-centre of a radio therapy treatment apparatus; irradiating the calibration phantom using the radio therapy treatment apparatus and determining the relative location of the centre of the calibration phantom and the iso-centre of the radio therapy treatment apparatus by analysing images of the irradiation of the calibration phantom; applying an offset corresponding to the determined relative location of the centre of the calibration phantom and the iso-centre of the radio therapy treatment apparatus to the calibration phantom; utilising a stereoscopic camera system to obtain images of the relocated calibration phantom to which the offset has been applied; and processing the obtained images to set the co-ordinate system of the stereoscopic camera system relative to the iso-centre of the radio therapy treatment apparatus.

2 . The method of calibrating a stereoscopic camera system for use with a radio therapy treatment apparatus of claim 1 , further comprising:
processing the obtained images of the relocated calibration phantom to which the offset has been applied to generate a 3D computer model of the surface of the repositioned calibration phantom; and comparing the generated 3D computer model of the surface of the repositioned calibration phantom with a 3D computer model of the surface of the calibration phantom positioned at the iso-centre of the treatment apparatus.

3 . The method of calibrating a stereoscopic camera system for use with a radio therapy treatment apparatus of claim 2 , further comprising:
generating a 3D computer model of the surface of the calibration phantom positioned at the iso-centre of the treatment apparatus by:
utilising the stereoscopic camera system to obtain images of the calibration phantom positioned at the estimated location for the iso-centre of the radio therapy treatment apparatus;
processing the obtained images of the calibration phantom positioned at the estimated location for the iso-centre of the radio therapy treatment apparatus to generate a 3D computer model of the surface of the calibration phantom positioned at the estimated location for the iso-centre of the radio therapy treatment apparatus; and
applying an offset corresponding to the determined relative location of the centre of the calibration phantom and the iso-centre of the radio therapy treatment apparatus to the generated 3D model of the surface of the calibration phantom positioned at an estimated location for the iso-centre of the radio therapy treatment apparatus.

4 . The method of calibrating a stereoscopic camera system for use with a radio therapy treatment apparatus of claim 1 , wherein positioning a calibration phantom with the phantom's centre at an estimated location for the iso-centre of a radio therapy treatment apparatus comprises placing the calibration phantom on a mechanical couch; and wherein applying an offset corresponding to the determined relative location of the centre of the calibration phantom and the iso-centre of the radio therapy treatment apparatus to the calibration phantom comprises instructing the mechanical couch to relocate in a manner corresponding to the offset.

5 . The method of calibrating a stereoscopic camera system for use with a radio therapy treatment apparatus of claim 4 , wherein placing the calibration phantom on a mechanical couch comprises:
placing an adjustable table on the mechanical couch; fixing the calibration phantom on the adjustable table; and levelling the adjustable table.

6 . The method of calibrating a stereoscopic camera system for use with a radio therapy treatment apparatus of claim 5 , wherein the adjustable table includes a spirit level and wherein levelling the adjustable table comprises adjusting the adjustable table until the spirit level indicates that the adjustable table is level.

7 . The method of calibrating a stereoscopic camera system for use with a radio therapy treatment apparatus of claim 1 , wherein the calibration phantom comprises:
a calibration phantom containing one or more calibration targets and analysing images of the irradiation of the calibration phantom comprises determining the relative location of the centre of the calibration phantom and the iso-centre of the radio therapy treatment apparatus by comparing the locations of the one or more targets in images of the irradiated calibration phantom irradiated with the treatment apparatus being in a number of different positions.

8 . The method of calibrating a stereoscopic camera system for use with a radio therapy treatment apparatus of claim 1 , further comprising:
irradiating the relocated calibration phantom to which the offset has been applied using the radio therapy treatment apparatus and determining the relative location of the centre of the relocated calibration phantom and the iso-centre of the radio therapy treatment apparatus by analysing images of the irradiation of the relocated calibration phantom; and applying an offset corresponding to the determined relative location of the centre of the relocated calibration phantom and the iso-centre of the radio therapy treatment apparatus to the relocated calibration phantom; wherein processing the obtained images to set the co-ordinate system of the stereoscopic camera system relative to the iso-centre of the radio therapy treatment apparatus comprises utilising a stereoscopic camera system to obtain images of the relocated calibration phantom to which the offset has been applied; and processing the obtained images to set the co-ordinate system of the stereoscopic camera system.

9 . The method of calibrating a stereoscopic camera system for use with a radio therapy treatment apparatus of claim 5 , wherein the calibration phantom contains multiple targets, the method further comprising:
replacing the calibration phantom containing multiple targets fixed to the adjustable table with a second calibration phantom containing a single target; irradiating the second calibration phantom fixed to the adjustable table using the radio therapy treatment apparatus and determining the relative location of the centre of the second calibration phantom and the iso-centre of the radio therapy treatment apparatus by analysing images of the irradiation of the second calibration phantom; and causing the mechanical couch to apply an offset corresponding to the determined relative location of the centre of the second calibration phantom and the iso-centre of the radio therapy treatment apparatus to the second calibration phantom; wherein processing the obtained images to set the co-ordinate system of the stereoscopic camera system relative to the iso-centre of the radio therapy treatment apparatus comprises utilising a stereoscopic camera system to obtain images of the relocated second calibration phantom to which the offset has been applied; and processing the obtained images to set the co-ordinate system of the stereoscopic camera system.

10 . A method of calibrating a stereoscopic camera system for use with a radio therapy treatment apparatus, the method comprising:
positioning a calibration phantom with the phantom's centre at an estimated location for the iso-centre of a radio therapy treatment apparatus; utilizing a stereoscopic camera system to obtain images of the phantom and processing the images to generate a 3D computer model of the surface of the phantom; irradiating the calibration phantom using the radio therapy treatment apparatus and determining the relative location of the centre of t

Assignees

• Vision Rt Ltd

Inventors

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

Classifications

• G06T7/85

  Stereo camera calibration · CPC title

• A61B6/584

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

• A61N2005/1076

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

• G06T7/0012

  Biomedical image inspection · CPC title

• G06T2207/30004

  Biomedical image processing · CPC title