An aperture can be added for any snout that has slabs defined for use in the site specific machine model. The user also had the ability to utilize apertures as desired in PBS beam planning.

• From within the PBS Beam Task you may add an aperture to a beam by selecting the Aperture Task Block clicking the “Add One” button.

• Your target structure is automatically selected from your beam information so you need to only specify the number of millimeters you want to expand your aperture around the target structure using the “Margin” option to generate your initial aperture shape. For this example we will give a margin of 10mm around the PTV7920.
  • Your aperture should now appear in the BEV display window.
  • As seen in the example the aperture is created so that it there is a 10mm margin from the PTV7920 to the edge of the aperture.

• In many cases you may have nearby critical structures that must be avoided. You can add an “Avoidance Structure” to your aperture design by clicking on the “Add Structure” dropdown and selecting a structure.
• Once added you can now specify a margin (mm) around this structure if desired (note negative margins will reduce the size of the blocked area of the structure).
  • You may also choose to occlude the structure by the target or not using the “Occlude by Target” option. For the following examples we will use the Urethra as it shows a dramatic example of differences of using or not using the “Occulde by Target” option. A 2mm margin was applied to the Urethra for the following examples.
    • By checking the “Occlude by Target” box you are choosing to give the target priority over the structure in the view you are looking at in the DRR. In other words the visible target (target in front of this structure) will not be blocked by the aperture. Note that just the inferior edge of the Urethra is blocked by the aperture. The part of the Urethra that is behind the PTV7920 is not blocked.
    • If you leave the “Occlude by Target” unchecked, you are choosing to give the structure priority over the target. This means you will block the entire structure regardless of its position relative to the target. In this example the aperture blocks out all of the Urethra.
• You may add as many Avoidance Structures as needed to design your aperture shape.

• The “Shape Smoothing” section allows you to smooth the aperture if needed.
• The smoothing level value can be set from 0-20, with zero applying no smoothing and higher numbers increasing the smoothness of the aperture. More details regarding the smoothing algorithm and process can be found here <link>.

• Manual edits allow you to draw on the BEV in order to manually edit the aperture shape.
• First, set the radius of the editing tool to the desired size (you can directly type a size or use the -/+ on either side to increment the size)
• You are now free to draw manual override regions directly on the BEV. You draw by simply clicking and dragging the mouse at the desired positions.
  • The editing tool automatically switches between adding or subtracting material based on the position of the tool when the mouse is first clicked (i.e. when starting each new draw operation).
    • When outside the aperture, you edit the aperture by pushing in/subtracting and your edit regions are drawn in a blue color. The hashed red line denotes the original placement of the aperture.
    • When inside the aperture, you edit the aperture by pushing out/adding and your edit regions are drawn as the color of your target.
  • Once done with manually editing, click the “Disable Editing” button to end the process.
  • Note that your edits and the resulting aperture shape will still show on the DRR (BEV) and your edits will remain active even when changing other options.
  • If you need to remove the manual edits for any reason, you may do so by pressing the “Clear Edits” button. Pressing this button will remove ALL manual edits for this aperture.

• If you wish to remove the aperture from this beam, simply press the “Remove Aperture” button at the bottom of the Aperture Task Block