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The Clinical Impact of VOLO Optimization in CyberKnife Treatment Planning

E Schueler*, A Lo , C Chuang , S Soltys , L Wang , Stanford University, Stanford, CA


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: The purpose of this study was to investigate the clinical impact of the VOLO optimizer on treatment plan quality and clinical treatment efficiency as compared to the previous Sequential optimizer.

Methods: Treatment plan quality was evaluated on three categories of patients: Brain Simple(G1), Brain Complex(G2), and Spine Complex(G3). Five patients per category were identified and treatment plans were generated using both Sequential and VOLO optimizer with Iris and MLC collimation (50 total plans were compared) with same clinical constraints. Metric evaluation included estimated treatment time, MUs delivered, conformity index (V100%/PTV), and volume receiving 50% of prescription dose (V50%). Furthermore, the clinical impact of the VOLO optimizer was evaluated through statistical analysis of the patient population treated during the 4 months before (n=297) and during the 4 months after (n=285) VOLO introduction. Treatment time, number of beams, and number of MUs delivered were compared.

Results: Significant MU and time reductions were observed for all three categories planned. MU reduction ranged from -14.3% (G1 Iris) to -19.8% (G3 MLC), and time reduction ranged from -14.3% (G1 Iris) to -50.2% (G2 MLC). Mean CI changes ranged from -0.01 (G1 with Iris) to -0.08 (G3 with MLC). Mean V50% was slightly reduced for all three categories (-3.2% for G1 Iris to –0.6% G3 Iris) except for G3 MLC cases (+4.3%). The patient statistical analysis before and after VOLO introduction for patients using 6D Skull tracking with fixed cone, 6D Skull tracking with Iris and Xsight Spine tracking with Iris were -5%, -22%, and -18% for treatment time reduction, -1%, -22%, -28% for beam reduction and -3%, -22%, -28% for MU reduction, respectively.

Conclusion: The VOLO optimizer maintains or improves the plan quality while decreases the plan complexity and improves treatment efficiency. We anticipate increase in patient throughput with the introduction of VOLO optimizer.


Treatment Planning, Stereotactic Radiosurgery, Dosimetry


TH- External beam- photons: cyberknife

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