Measurement Instructions - mwgeurts/viewray_mlc GitHub Wiki

The following steps illustrate how to acquire and process 90 degree SNC IC Profiler measurements on the ViewRay MRIdian treatment system. As discussed below, these instructions recommend using 90 and 270 degree Head 3 10.5 cm x 10.5 cm fields to verify the position of the IC Profiler prior to acquiring the MLC data. Similar measurements may be acquired at 270 degrees using the same IC Profiler setup, and at 0 and 180 degrees by orienting the IC Profiler in the coronal position.

Contents

Set up the IC Profiler

  1. Attach the SNC IC Profiler to the IC Profiler jig
  2. Connect the IC Profiler to the Physics Workstation using the designated cable
  3. Launch the SNC Profiler software on the Physics Workstation
  4. Select the most recent Dose calibration from the dropdown box
  5. Select the most recent array Calibration from the dropdown box
  6. Verify the mode is continuous by clicking the Control menu

Orient the IC Profiler in the Sagittal Position

  1. Place the SNC Profiler jig on the couch at virtual isocenter and orient the jig in the Sagittal orientation, as shown
  2. The top of the profiler will be facing the IEC+X axis
  3. The electronics will be on the facing upwards (IEC+Y axis)
  4. Place an aluminum level on the front face of the IC Profiler as shown
  5. Verify the profiler is parallel with the IEC Sagittal plane
  6. Use the leveling feet on the jig to adjust if necessary
  7. Laterally adjust the jig until the overhead IEC X laser is aligned to the front face of the IC Profiler
  8. Record the current couch position
  9. Use the Couch Control Panel to move the couch and IC Profiler +0.9 cm in the IEC+X direction
  10. The detector plane of the IC Profiler should now be at isocenter
  11. Vertically and Longitudinally align the IC Profiler to the crosshairs using the wall IEC Y and IEC Z laser
  12. Press the ENABLE and ISO buttons on the Couch Control Panel to move the couch from virtual to mechanical isocenter
  13. On the ViewRay TPDS, select Tools > QA Procedure and select the Calibration tab
  14. Select an arbitrary phantom and click Load Phantom
  15. Under Beam Setup and Controls, select Head 3
  16. Set Delivery Angle to 90 degrees
  17. Under MLC Setup, set the following MLC positions: X1/Y1 = -5.25 cm, X2/Y2 = +5.25 cm
  18. Click Set Shape to apply the MLC positions
  19. Enter 30 seconds as the Beam-On Time
  20. Click Prepare Beam Setup
  21. Click Enable Beam On
  22. Press Beam On on the Treatment Control Panel
  23. In the SNC Profiler software, click Start
  24. When asked if the new measurement is continuous, click Yes
  25. Wait for the beam to be delivered
  26. Click Stop on the Profiler Software
  27. Enter the Delivery Parameters and Save the File
  28. Click on the Setup tab
  29. Enter the gantry angle
  30. Set the SSD to 100 cm
  31. Check Symmetric Collimators
  32. Enter the field size as 10.5 cm x 10.5 cm
  33. Click on the General tab
  34. Under Description, type Head #, where # is the head number (3 in this instance)
  35. Click OK
  36. When asked to save the file, choose Multi-Frame type and save the results to H3 G90 10p5.prm
  37. Move the Gantry to 270 degrees and repeat the exposure, saving the results to H3G270 10p5.prm
  38. Review the 90 degree and 270 degree Profiler Y-Axis
  39. Calculate the average Beam Center for both gantry angles
  40. Verify the average of the two values is within +/- 0.02 cm
  41. If not, add the average value to the couch position IEC-Z value and repeat the measurements
  42. Review the 90 degree and 270 degree Profiler X-Axis
  43. Verify the average of the two values is within +/- 0.2 cm
  44. If not, add the average value to the couch position IEC-Y value and repeat the measurements
  45. Once both axes are within specification, continue below to deliver the six MLC fields
  46. Record the final couch positions. If the system must be restarted, the couch should be verified before continuing

Collect MLC Data

  1. On the ViewRay TPDS, select Head 1 under Beam Setup and Controls
  2. Set Delivery Angle to 90 degrees
  3. Under MLC Setup, set the following Strip 1 MLC positions: X1 = -12.5 cm, X2 = -7.5 cm, Y1 = -13.65 cm, Y2 = +13.65 cm
  4. Click Set Shape to apply the MLC positions
  5. Enter 30 seconds as the Beam-On Time. A screenshot of all Calibration settings is provided
  6. Click Prepare Beam Setup
  7. Click Enable Beam On
  8. Press Beam On on the Treatment Control Panel
  9. In the SNC Profiler software, click Start
  10. When asked if the new measurement is continuous, click Yes
  11. Wait for the beam to be delivered
  12. Click Stop on the Profiler Software
  13. Enter the Delivery Parameters and Save the File
  14. Click on the Setup tab
  15. Gantry Angle in the window that appears (Setup Tab)
  16. Set the SSD to 100 cm
  17. Uncheck Symmetric Collimators
  18. Enter the field size based on the X1/X2 and Y1/Y2 parameters above
  19. Click on the General tab
  20. Under Description, type Head #, where # is the head number (1 in this instance)
  21. Click OK
  22. When asked to save the file, choose Multi-Frame type and save the results to H1 G90 Strip1.prm
  23. Repeat measurements at the same head and gantry angle for the remaining strips, using the field sizes in the above table
  24. In the SNC IC Profiler software, after completing all six exposures, export the data to ASCII format by selecting Export > SNC ASCII
  25. In the message box that appears, verify the default settings are selected and specify a destination file
  26. Repeat the steps above for Head 2 and Head 3, both at 270 degrees

Analyze MLC Data

  1. Execute the AnalyzeMLCProfiles.m MATLAB script
  2. Under Head 1, click Browse to load the SNC IC Profiler ASCII export for the first gantry angle
  3. When requested, select the Gantry angle
  4. Continue to load the remaining angles and heads
  5. Review the resulting profile comparisons and edge offset plots, as shown in the example
  6. Verify that each profile looks as expected and that no data points (particularly those around the FWHM limits) appear distorted due to noise or measurement error
  7. Verify that each X1 and X2 field edge differences are within +/- 2 mm for all six positions
  8. The minimum and maximum deviations are listed in the statistics table at the bottom