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Knowledge Based Planning: Standardization of Stereotactic Radiotherapy Treatment Plans Using An Ensemble Mapping in a Large Volume Library Plans

B Sarkar

B Sarkar1*, (1) AMRI Cancer Centre, Kolkata,


SU-I-GPD-T-577 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To minimize the inter-planner variation and standardize the stereotactic (SRS/SRT) treatment plans using ensemble mapping in a large library of the stereotactic treatment plans.

Methods: An ensemble of 150 VMAT based brain SRS/SRT were categorised on basis of (1) PTV dose coverage challenged by presence of organ at risk (OAR) or not (2) prescription dose (3) Number of PTVs (4) laterality (left /right) (5) tumour volume (6) shortest distance between OAR and PTV (7) centre to centre distance between OARs and PTV (8) lateral dimension of external contour (brain). Further, on arrival of a new patient most appropriate library plan was chosen on the basis of above categorisation using ensemble mapping. Most appropriate library plan was copied with all parameters unchanged to the new patient. Optimization and dose calculation was carried out in MONACO (v 5.00.04) with no or very minimal changes in the optimization constrain and arc length. Another independent treatment plan using the same beam configuration arc was generated by an experience medical physicist for comparison.

Results: Independent plan(IP) was better than the knowledge based plans (KBP) in PTV coverage and dose conformity. However PTV coverage (V100%) and OAR doses were not statistically different between two sets. However for those patients where PTV is isolated from OAR and dose coverage is not challenged by presence of OAR, IP yields a better dose conformity than KBP which was statistically significant (p<0.04). IP requires on average 3.5 optimization/dose calculation which is about 3.5-5 hrs, where KBP does not require more than 1.5 runs (1.5-2)hrs.

Conclusion: KBS plans save a considerable planning time and almost independent of the treatment planner skill and knowledge. IP produce a better dosimetric result credited to an experience treatment planar with a high planning time. KBP works well with Monte Carlo planning system like MONACO.

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