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Improvement of Dose Distributions in Volumetric Modulated Arc Therapy (RapidArc) with Jaw Tracking Technique for Lateralized Target

R Diaz Moreno*, A Alarcon , O Apaza , L Paredes , C Venencia , Instituto Zunino, Cordoba - ARGENTINA


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: Jaw tracking technique (JTT) in RapidArc treatments allows blocking unwanted leakage radiation. For lateralized patient's targets, keeping the isocenter centered can be helpful to avoid collisions, spare couch motions and decrease treatment times. In this work, dosimetric differences between JTT and static jaw technique (SJT) in RapidArc treatments were compared for lateralized targets with isocenter in patient’s midline.

Methods: Two pancreatic SBRT plans were replanned with JTT. Plans were created using a 6X beam of a TrueBeam STx and Eclipse v15.1 (Varian). PTV's D95%, D2% and Paddick's conformity index (CI) were compared. V5Gy, V10Gy, V20Gy and Dmean of normal tissue (Body-PTV) were compared. Portal dosimetry images were taken for verification.

Results: The variation of PTV’s D95% and D2% between JTT and SJT plans was less than 2%. Both techniques had identical plans CI. Increased dose ring shaped areas were observed in SJT plans. Dose in those areas decreased from 7.13 Gy to 5.44 Gy and from 10.4 Gy to 6.53 Gy with JTT. Portal images of SJT plans showed radiation leakage between closed opposed leaves with a peak about 30% of the maximum fluence. JTT showed a normal tissue Dmean reduction compared to SJT in both plans of -12% and -20% respectively. JTT showed a normal tissue volume reduction compared to SJT for the first plan of V5Gy: -13%, V10Gy: -8.3% and V20Gy: -3.8% and for the second one of V5Gy -18%, V10Gy: -25% and V20Gy: -16%.

Conclusion: JTT plans were capable of delivering equivalent PTV coverage with better healthy tissue protection.


Not Applicable / None Entered.


TH- External beam- photons: treatment planning/virtual clinical studies

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