Measurement Instructions - mwgeurts/viewray_fielduniformity GitHub Wiki

The following steps illustrate how to acquire and process 90 degree SNC IC Profiler measurements on the ViewRay MRIdian treatment system. Similar measurements may be acquired at different gantry angles using the same reference profile so long as the IC Profiler is set up the same way relative to the entrance beam.

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
  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 = -13.65 cm, X2/Y2 = +13.65 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. On the Treatment Control Panel, wait for the ready light to appear, then press Beam On
  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 27.3 cm x 27.3 cm
  33. Click on the General tab
  34. Under Description, type Head #, where # is the head number (1 in this instance)
  35. Click OK
  36. When asked to save the file, choose Multi-Frame type and save the results to H1 G90 27p3.prm
  37. Repeat for Heads 2 and 3

Analyze Field Uniformity Data

  1. Execute the FieldUniformity in MATLAB
  2. Under Head 1, click Browse to load the SNC IC Profiler H1 G90 27p3.prm Multi-Frame export
  3. Continue to load the remaining heads
  4. Review the resulting profile comparisons and statistics
  5. Verify that each profile looks as expected and that no data points (particularly those in the central 80% of the field) appear distorted due to noise or measurement error
  6. Verify that the MLC X and Y flatness and areal symmetry are within +/- 2% of their baseline values for all three heads
  7. Verify that the time difference between the Expected and Measured beam on time are within 0.1 seconds
  8. Click Print Report to generate a PDF report for documentation in the QMP