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--- planning:userguide:tutorials:pbs_beams [2019/08/20 15:25] – [General Settings] dwright
+++ planning:userguide:tutorials:pbs_beams [2021/07/29 18:28] (current) – external edit 127.0.0.1
@@ Line 22: / Line 22: @@
 === PBS specific ===
+For PBS beams the following additional options will be available:
   * //**Geometric Target**// is used for approach and device creation. You may choose an existing target or create a new structure. For this example we chose the PTV_7920 as the geometric target. The geometric target will be used to define the extents of the aperture (if used) and will be linked to the isocenter position (if target centroid is selected in the approach block).
   * //**Spot Target**// is used to define the extent of the PBS spot placements for the beam. The spot target can either match the geometric target, or the user can choose to use the target for the fraction group in which the beam is used (useful for allowing the same geometric beam to be used in multiple fraction groups by simply recomputing the spot positions based on the fraction group target). {{ :planning:userguide:tutorials:pbs_select_target.png?500 |}}
 === SOBP specific ===
+For SOBP beams the following additional options will be available:
   * //**Target**// is used for approach and device creation, and it can be either a structure or an existing beam.
-  * If the target selected is an existing beam, the new beam becomes a //**Patch beam**// or //**field**//. Thus, the targeted beam becomes a parent of the patch beam (child).
-    * The patch dose field box is then enabled, allowing users to enter a dose value amount. This value helps identify areas of the targeted volume that received less than then the entered dose amount from the parent beam.
+{{ :planning:userguide:tutorials:sobp_beam_general_settings_target_selection.png?300 |}}
-    * The patch beam will then apply the patch dose amount to the remaining volume in the patch beam's path.
-    * To create a patch beam of an existing patch beam, select the desired patch beam as the target.
+  * If the target selected is an existing beam, the new beam becomes a //**Patch beam**//. Thus, the targeted beam becomes a parent thru-beam of the current patch beam (child).
-    * Once a beam is designated as a patch, it cannot change back to a standard thru-beam. Thus, a new SOBP beam must be created.
+    * The patch dose field box is then enabled, allowing users to enter a dose value amount. The parent beam's target will reduced such that any portion receiving a dose from the parent beam that is greater than this amount will be ignored when designing the patch beam range compensator. In other words, the target of the patch beam becomes the target of the parent beam, minus the volume enclosed by the isodose surface (compute only for parent beam) at the defined patch dose value. This patch beam target can be viewed in the Display UI and toggled on and off in the right hand side beam controls.
+    * Patch beams can also be "chained" beyond a single parent-child pair by creating a beam and selecting the desired patch beam as the target.
+    * Also note, that once a beam is designated as a patch and added to a fraction group, it cannot be changed back to a standard non-patch beam. In such cases, you must either remove the beams from the Fraction Group first, or a new SOBP beam must be created.
 ==== Beam Approach ====