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Comparing IMRT Versus VMAT Treatment Plan Quality for SRS Spine Patients

V Ulizio*, V Arora , D Pearson , University of Toledo, Toledo, OH


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: The purpose of this study is to compare IMRT versus VMAT treatment plan quality for SRS spine patients utilizing the Pinnacle planning systems. The plans were evaluated using RTOG and Paddick Conformity Indices and a common Gradient Index.

Methods: For this study we evaluated 14 treatment plans optimized in the Pinnacle treatment planning system. For each patient, the objectives from the original clinically treated IMRT plans were used to create VMAT plans. The VMAT plans also used the same energy as the original plan and 6FFF was the most commonly used energy. All plans were normalized to match the original plan. The various indices were then evaluated and compared.

Results: VMAT had a worse average RTOG Conformity Index (RTOG CI) at 1.922 compared to IMRT’s 1.528. The Paddick Conformity Index (PCI) was better however 0.630 for VMAT and 0.608 for IMRT. The Gradient Index (GI) was a lot better with VMAT than with IMRT at 6.30 compared to 9.43.

Conclusion: We found that the VMAT spine plans were superior compared to the other plans with better PCI and GI values. The plans overall visually looked better with VMAT as well, as the low dose was more conformal to the target. VMAT is suggested to be used for future SBRT Spine treatments as they have shown to be superior and also have the benefit of faster treatment times.


Not Applicable / None Entered.


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

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