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--- planning:userguide:tutorials:finding_optimal_plan [2019/02/19 15:27] – [Astroid Optimization] anegron
+++ planning:userguide:tutorials:finding_optimal_plan [2021/07/29 18:28] (current) – external edit 127.0.0.1
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-====== Astroid Optimization ======
+====== Astroid Optimization (PBS) ======
-With intensity modulated treatment plans the variety of possible dose distributions is quite large. Typically if a physician does not like a plan they will request it to be re-run. This requires the planner to input new constraints and objectives and a new plan to be run from the beginning of the optimization process. This is a time consuming process. Astroid eliminates this cycle using a Multi-Criteria Optimization (MCO) approach that allows planners and physicians to visualize the trade-offs of target volume coverage vs reduced dose to the OAR's in real time. MCO treatment planning is based on a set of Pareto optimized plans, where a plan is considered Pareto optimal if it satisfies all the constraints and none of the objectives can be improved without worsening at least one of the other objectives. So instead of creating just one plan, Astroid creates a set of optimal plans that satisfies the treatment plan constraints and puts an interactive exploration of the objectives at the planners and physicians fingertips via a unique, highly intuitive, solution navigation slider bar system. The user is able to select the MCO optimization algorithm from a list defined in the site configuration settings. The default option is the first algorithm in this site level list.{{ :planning:userguide:tutorials:mco_selection.png?400 |}}
+With intensity modulated PBS treatment plans the variety of possible dose distributions is quite large. Typically if a physician does not like a plan they will request it to be re-run. This requires the planner to input new constraints and objectives and a new plan to be run from the beginning of the optimization process. This is a time consuming process. Astroid eliminates this cycle using a Multi-Criteria Optimization (MCO) approach that allows planners and physicians to visualize the trade-offs of target volume coverage vs reduced dose to the OAR's in real time. MCO treatment planning is based on a set of Pareto optimized plans, where a plan is considered Pareto optimal if it satisfies all the constraints and none of the objectives can be improved without worsening at least one of the other objectives. So instead of creating just one plan, Astroid creates a set of optimal plans that satisfies the treatment plan constraints and puts an interactive exploration of the objectives at the planners and physicians fingertips via a unique, highly intuitive, solution navigation slider bar system.
 //Constraints// play an important role in the optimization process, as they bound the solution space and ensure your navigation process is focused only on plans that meet your non-negotiable, highest priority dosimetric needs. It should be noted that if the //constraints// are too tight, there may be no feasible plans. However, if the //constraints// are too loose, too many solutions will exist and the navigation will be too broad to provide adequate resolution over the truly clinically useful plans. Therefore care should be taken to ensure appropriate constraints are set, which is facilitated using the Astroid //Feasibility// check feature. So while constraints supply hard limits, //objectives// are the negotiable goals, they do not have a hard level that must be obtained, but "pushing" them harder does result in benefit to the patient. The number and type of //objectives// chosen should be such that all the relevant trade-offs can be demonstrated and explored.
+===== Optimizer Algorithm Selection =====
+The user is able to select the MCO optimization algorithm from a list defined in the site configuration settings. The default option is the first algorithm in this site level list of pluggable_functions designated with the mco_optimizer key.
+As of Planning 2.3.2 the available optimizers are Art3+O and Nymph. Both optimizers use the same constraints and objectives. However Nymph does not use a separate feasibility stage and has it built in to the optimization step.
+{{ :planning:userguide:tutorials:mco_selection.png?400 |}}
+===== PBS Fraction Groups =====
+{{page>planning:userguide:tutorials:fraction_group&noheader}}
+===== Optimization Constraints =====
+==== About Constraints ====
+//Constraints// can be specified at various levels (//Plan, Fraction Group, Target/Beam Set//) with Astroid and they will affect different groups of beams depending on their level. //Constraints// at the //Plan// level are applied to the total dose resulting from all beams. //Constraints// at the //Fraction Group// level are applied to the total dose resulting from only the beams in the current Fraction Group. //Constraints// at the //Target/Beam Set// level are split evenly and applied individually to each Beam Set. In other words, the //Constraint// dose is divided by the number of //Beam Sets// in the //Target//, and this dose is then applied as a constraint to each Beam Set, so that either SFUD and IMPT can be achieved (see [[planning:userguide:tutorials:fraction_group|Fraction Groups]]). The section below will provide a walk through of the different levels and how constraints are applied at each one.
+It should be noted that all constraints are considered "hard limits"- values that __must be__ achieved. //Constraints// drive the feasibility calculation- whether the plan is achievable and should be used to ensure certain minimal clinical parameters are met.
+The following constraint types are available. Note certain constraints are available only for //Target// type structures.
+     * **Min**: The minimum dose the structure must receive
+     * **Max**: The maximum dose the structure may receive
+     * **Min Mean**: The minimum mean dose a structure must receive
+      * This will drive the dose up across the structure
+     * **Max Mean**: The maximum mean dose a structure may receive
+      * This will limit the mean dose across the structure
+     * **Overdose**: The maximum sum of the overdose that a structure may receive (//not available for ART3+O optimizer//)
+      * This will limit the total volume-weighted overdose (dose above a given threshold) that a structure receives, driving down hot spots
+     * **Underdose**: The maximum sum of the underdose that a structure may receive (//not available for ART3+O optimizer//)
+      * This will limit the total volume weighted underdose (dose below a given threshold) that a structures, driving up cold spots
+     * **Hot Spot Vol**: The maximum mean dose to the hottest portion of a structure (//not available for ART3+O optimizer//)
+      * This will keep the mean dose to the hottest portion of a structure below the given limit; portion is set as a % vol and the limit is the max mean dose allowed to that portion of the structure
+     * **Cold Spot Vol**: The minimum mean dose to the coldest portion of a structure (//not available for ART3+O optimizer//)
+      * This will keep the mean dose to the coldest portion of a structure above the given limit; portion is set as a % vol and the limit is the min mean allowed to that portion of the structure
+The user can choose to apply one or multiple of these constraints to any number of structures.
+==== Working with Constraints ====
+=== Working with Fraction Group and Target/Beam Set Constraints ===
+//Constraints// at the //Fraction Group// level are applied to the total dose resulting from only those beams in the current //Fraction Group//. //Constraints// at the //Target / Beam Set// level are equally split among the Beam Sets within the Target and are applied to the total dose resulting from the beams in each of the Beam Sets. The following steps are a brief walkthrough for creating a max constraint of 79.2 Gy(RBE) to the PTV for the whole Fraction Group, and then creating two SFO beams that each provide a minimum dose of 39.6 Gy(RBE). Note that this configuration with the max constraint at the Fraction Group Level is different than if we had put both the min and max at the Target / Beam Set level. In the case shown, it is only the total dose from the two beams that is constrained to be below 73 Gy(RBE). Had both constraints been placed at the Target Level, then each beam would instead be constrained to a max of 36.5 Gy(RBE).
+  - Select the //Fraction Group// if it has been created or create a new one by clicking //Create New Fraction Group//
+  - Choose the prescription, number of fractions to be treated with this Fraction Group
+  - Choose the type of treatment (SFO, IMPT, Advanced) and target {{ :planning:userguide:tutorials:fx_group_start.png?300 |}}
+  - Choose the //Beams// to be treated
+  - Choose the //Target// to be treated
+    - Assign the dose constraints to the //Target//
+    - The assigned constraint doses at this level will be divided evenly among the //Beams// to the //Target//, which allows for quick creation of SFO treatments {{ :planning:userguide:tutorials:fx_group_beams_and_target.png?300 |}}
+=== Working with Plan Constraints ===
+//Constraints// at the //Plan// level are applied to the total dose across all beams.
+  - Open the //Constraints// sub block contained in the //Constraints/Feasibility// block and choose the //Edit// button.
+  - Choose from the drop down the structure or structures to which constraints should be added
+  - Define what constraint(s) should be applied to each structure by choosing the constraint and entering the dose
+  - Follow this and enter the constraints for all applicable structures. {{ :planning:userguide:tutorials:constraints_2.png?300 |}}
+  - When finished click the //OK// button.
+  - Once all the Constraints have been set the user can either start the Feasibility by choosing //Calculate// or move on to defining the Objectives
 ===== Feasibility and Constraints =====
-After the //Constraints// have been entered, the user may start the //Feasibility// calculation by clicking //calculate// in the //Feasibility// block. The //Feasibility// calculation is based solely on the //constraints// and it should be used to ensure that is is possible to met the specified constraints. The //Feasibility// calculation may be an iterative processes in order to get appropriate constraints established for a particular plan. In other words, the user may need to enter one or more constraints, check the feasibility, then progressively tighten the constraints and re-check the feasibility until the plan is no longer feasible, then back-off to the last feasible values. It is recommended practice to start by obtaining a feasible plan utilizing only target //Constraints// then add OAR //Constraints// as desired. Remember, using a narrow range of constraints can improve the optimizer performance and improve the resolution of the solution navigation.
+After the //Constraints// have been entered, the user may start the //Feasibility// calculation by clicking //calculate// in the //Feasibility// block. The //Feasibility// calculation is based solely on the //constraints// and, it should be used to ensure that it is possible to meet the specified constraints. The //Feasibility// calculation may be an iterative processes in order to get appropriate constraints established for a particular plan. In other words, the user may need to enter one or more constraints, check the feasibility, then progressively tighten the constraints and re-check the feasibility until the plan is no longer feasible, then back-off to the last feasible values. It is recommended practice to start by obtaining a feasible plan utilizing only target //Constraints// then add OAR //Constraints// as desired. Remember, using a narrow range of constraints can improve the optimizer performance and improve the resolution of the solution navigation.
 The user also needs to be aware of the impact of //Constraints// being set at the //Fraction Group// level versus the //Plan// level. For example, it is possible to have a //Constraint// set in the //Plan// level so that the whole dose to an OAR is given on one day and none on the other day. This could happen when there are two //Fraction Groups// and the OAR dose is not split between the two by using Fraction Group level constraints.
+===== Optimization Objectives =====
+//Objectives// communicate to the optimizer the goals that are important to strive for in your plan. //Objectives// are set at the //Plan// level under //Plan Constraints/Objectives// and they apply to the total, combined dose from all beams. //Objectives// are not given any relative importance at this point (i.e. their order within the list is not meaningful). The //Objectives// drive the solution of the Multi Criteria Optimization (MCO) and for each //Objective//, a corresponding //Navigation Slider// will be presented to allow for exploration of trade-offs in the case of competing objectives (for more information about the MCO process and how objective importance/weighting is handled in Astroid refer to [[planning:userguide:tutorials:finding_optimal_plan|this article]]).
+The following objective selections are available in Astroid:
+    * **min_max**: Minimize the maximum dose within a structure (drive dose down)
+    * **max_min**: Maximize the minimum dose within a structure (drive dose up)
+<WRAP 1000px center><WRAP left>[{{ :planning:userguide:tutorials:objectives_min_max.png?390 | min_max: Minimize the Max Dose }}]</WRAP><WRAP right>[{{ :planning:userguide:tutorials:objectives_max_min.png?390 | max_min: Maximize the Min Dose}}]</WRAP></WRAP><WRAP clear></WRAP>
+    * **min_mean**: Minimize the mean dose within a structure (drive dose down)
+    * **max_mean**: Maximize the mean dose across the structure (drive dose up)
+    * **min_overdose**: Minimize the high dose within a structure
+      * Dose will be driven down only until the specified limit is reached (this is often more relevant that min_max, since it may not be beneficial to continue minimizing beyond a certain dose level)
+    * **min_underdose**: Minimize the low dose within a structure
+      * Dose will be driven up only until the specified limit is reached (this is often more relevant that max_min, since it may not be beneficial to continue maximizing beyond a certain dose level)
+<WRAP 920px center><WRAP left>[{{ :planning:userguide:tutorials:objectives_min_over.png?390 | min_overdose: Minimize the high dose}}]</WRAP><WRAP right>[{{ :planning:userguide:tutorials:objectives_min_under.png?390 | min_underdose: Minimize the low dose}}]</WRAP></WRAP><WRAP clear></WRAP>
+    * **min_hot_spot**: Minimize the mean dose to the hottest portion of a structure (//not available for ART3+O optimizer//)
+      * The mean dose to the hottest portion of a structure will be driven down (i.e. the tail dose on the DVH); portion is set as a % vol of the structure
+    * **min_cold_spot**: Maximize the mean dose to the coldest portion of a structure (//not available for ART3+O optimizer//)
+      * The mean dose to the coldest portion of a structure will be driven up (i.e. the shoulder dose on the DVH); portion is set as a % vol of the structure
+==== Working with Objectives ====
+  - Open the //Objectives/Optimizer// sub-block contained in the //Optimization// block
+  - Choose a structure to which you wish to apply objectives
+  - Check the boxes to activate the desired objectives for the structure and then set the dose level if applicable
+<WRAP center>{{ :planning:userguide:tutorials:optimization_plan_objectives.png?200 |}}</WRAP>
+Once all the //Objectives// have been set, the user is ready to run the MCO solver, which is performed in the //Objectives/Optimizer// block.
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 If the user likes the adjustments that were made to the sliders they may click the //Save// button in the bottom right hand corner. This will save the objectives at their current position. If the user does not like the adjustments they have made to the sliders, they may hit the //Reset// button to reset all the objective sliders to their last saved state. The //Cancel// button will close the //Navigation// block in its current state.