Automatic calibration for device with controlled motion range

Patent metadata

Field	Value
Publication number	US-9406411-B2
Application number	US-201113184370-A
Country	US
Kind code	B2
Filing date	Jul 15, 2011
Priority date	Feb 8, 2011
Publication date	Aug 2, 2016
Grant date	Aug 2, 2016

Abstract

An apparatus includes a portion that moves along a guided path and a displacement gauge that outputs readings based on the portion's position on the guided path. The apparatus additionally includes an intermediate limit switch that is activated in response to the portion being moved to an intermediate position on the guided path. The apparatus also includes a processing device configured to calibrate the apparatus based on a first reading corresponding to a first position on the guided path and a second reading corresponding to a second position on the guided path. The processing device verifies the calibration based on a third reading corresponding to the intermediate position.

First claim

What is claimed is:

1. A variable aperture collimator comprising:
at least one leaf that moves along a guided path, wherein movement of the at least one leaf along the guided path causes an aperture of the variable aperture collimator to change;
a displacement gauge that outputs readings based on the at least one leaf's position on the guided path;
an intermediate limit switch that is activated in response to the at least one leaf being moved to an intermediate position on the guided path; and
a processing device to:
calibrate the apparatus based on a first reading corresponding to a first position on the guided path and a second reading corresponding to a second position on the guided path, the first position corresponding to a minimum aperture of the variable aperture collimator and the second position corresponding to a maximum aperture of the variable aperture collimator; and
verify the calibration based on a third reading corresponding to the intermediate position, wherein the third reading was generated in response to the intermediate limit switch being activated.

2. The variable aperture collimator of claim 1 , further comprising:
a first limit switch that is activated in response to the at least one leaf being moved to the first position on the guided path; and
a second limit switch that is activated in response to the at least one leaf being moved to the second position on the guided path;
wherein the processing device is to receive, from the displacement gauge, the first reading corresponding to the first position in response to the first limit switch being activated, the second reading corresponding to the second position in response to the second limit switch being activated and the third reading corresponding to the intermediate position in response to the intermediate limit switch being activated, wherein the intermediate position is between the first position and the second position.

3. The variable aperture collimator of claim 1 , wherein to calibrate the variable aperture collimator the processing device calculates a linear equation using the first reading and the second reading, the linear equation relating readings of the displacement gauge to positions along the guided path.

4. The apparatus variable aperture collimator of claim 3 , wherein to verify the calibration the processing device performs the following:
calculates a current intermediate position value based on applying the third reading of the displacement gauge to the linear equation;
compares the current intermediate position value to a stored intermediate position value; and
determines that none of a first limit switch, a second limit switch or the third limit switch has been moved out of alignment if the current intermediate position value matches the stored intermediate position value.

5. The variable aperture collimator of claim 3 , further comprising:
a carriage attached to the at least one leaf, the carriage having a plurality of rises, wherein each of the plurality of rises causes the intermediate limit switch to be activated at the intermediate position or at an additional position of the at least one leaf on the guided path;
wherein the processing device to:
receive one or more additional readings of the displacement gauge in response to the intermediate limit switch being activated at additional positions along the guided path;
calculate current values for the intermediate position and the one or more additional positions based on applying the third reading and the additional readings of the displacement gauge to the linear equation;
compare the current intermediate position value to a stored intermediate position value and the current additional position values to stored additional position values; and
verify the calibration if the current intermediate position value matches the stored intermediate position value and the current additional position values match the stored additional position values.

6. The variable aperture collimator of claim 5 , further comprising:
a flexure that rides the carriage, wherein the flexure flexes when the flexure encounters each of the plurality of rises, and wherein the intermediate limit switch is activated in response to the flexure flexing.

7. The variable aperture collimator of claim 1 , wherein the displacement gauge is one of a linear displacement gauge or an angular displacement gauge.

8. The variable aperture collimator of claim 1 , wherein the intermediate limit switch is one of a mechanical limit switch, a magnetic proximity switch or an optical proximity switch.

9. The variable aperture collimator of claim 1 , wherein to calibrate the variable aperture collimator the processing device generates a non-linear sensor model relating readings of the displacement gauge to positions along the guided path, wherein the non-linear sensor model is generated using the first reading, the second reading and a fourth reading corresponding to an additional intermediate position, wherein the fourth reading was generated in response to the intermediate limit switch being activated.

10. A method of calibrating a variable aperture collimator having at least one leaf that moves along a guided path, comprising:
calculating, by a processing device, a correlation factor using a first reading generated by a displacement gauge at a first position on the guided path and a second reading generated by the displacement gauge at a second position on the guided path, wherein the correlation factor relates readings of the displacement gauge to positions on the guided path, and wherein the first position corresponds to a minimum aperture of the variable aperture collimator and the second position corresponds to a maximum aperture of the variable aperture collimator;
calculating, by the processing device, a current third position value based on applying a third reading of the displacement gauge to the correlation factor, wherein the third reading was generated by the displacement gauge in response to an intermediate limit switch being activated at an intermediate position on the guided path;
comparing, by the processing device, the current third position value to a stored third position value; and
determining, by the processing device, that the device is properly calibrated if the current third position value matches the stored third position value.

11. The method of claim 10 , further comprising:
determining the first reading of the displacement gauge in response to a first limit switch being activated, wherein the first limit switch is activated as a result of the at least one leaf moving on the guided path to the first position;
determining the second reading of the displacement gauge in response to a second limit switch being activated, wherein the second limit switch is activated as a result of the at least one leaf moving on the guided path to the second position; and
determining the third reading of the displacement gauge in response to the intermediate limit switch being activated at the intermediate position, wherein the intermediate position is between the first position and the second position.

12. The method of claim 10 , further comprising:
determining one or more additional readings of the displacement gauge in response to the intermediate limit switch being activated or deactivated at additional positions on the guided path;
calculating current values for the additional positions based on applying the additional readings of the displacement gauge to the correlation factor;
comparing the current additional position values to stored additional position values; and
determining that the device is properly calibrated if the current a

Assignees

• Sayeh Sohail
• Asmerom George
• Ramraj Sankaralingam
• Gao Jian
• Kuduvalli Gopinath
• Accuray Inc

Inventors

• Sayeh Sohail
• Asmerom George
• Ramraj Sankaralingam
• Gao Jian
• Kuduvalli Gopinath

Classifications

• A61N5/1075

  for testing, calibrating, or quality assurance of the radiation treatment apparatus · CPC title

• A61N5/1045

  using a multi-leaf collimator, e.g. for intensity modulated radiation therapy or IMRT · CPC title

• G21K1/04 Primary

  using variable diaphragms, shutters, choppers · CPC title