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SU-E-T-622: A Rapid Hybrid VMAT-IMRT Planning Method Using an Abbreviated Beam Angle Optimization Search.

Abstract：

PURPOSE:To generate hybrid VMAT-IMRT treatment plans by utilizing an IMRT beam-angle-optimality (BAO) search under a commercially available TPS without the aid of custom optimization software or high performance computing. METHODS:The high dose modulation provided by IMRT beams can be exploited to improve the quality of VMAT treatments. To achieve this, a VMAT treatment was created where the gantry pauses at predetermined angles to deliver IMRT segments. To determine IMRT BAO, an IMRT plan ('poly-IMRT') was made with many beams (>30) equally spaced around the patient. For practical reasons and to reduce the total time to approximately 1 hour, BAO was approximated by removing one beam out of the set and noting the new objective score. Determining this'score penalty' for each of the beams serves as a proxy for true BAO. The hybrid plan was created by combining the VMAT arc with a user-determined number of top-ranked beams from the poly-IMRT set. The BAO from this approach was compared with a more rigorous method ('VMAT+1'), in which a VMAT plan was optimized with 1 IMRT beam at various angles, allowing a direct determination of objective score versus gantry angle. The overall hybrid planning process was demonstrated by creating separate plans for a SBRT lung patient, with dose normalized to the limiting maximum aorta dose. RESULTS:Large score penalties from poly-IMRT coincided with large score benefits from VMAT+1, indicating both methods identified the same optimal beams. The VMAT, IMRT, and hybrid plans delivered the prescription dose to 84.3%, 85.6% and 87.7% of the PTV and had homogeneity indices of 1.38, 1.41, and 1.32 respectively. Normal tissue doses were within 0.5%. CONCLUSION:The presented method can create hybrid VMAT-IMRT plans which combine delivery efficiency with improved target coverage. The planning process takes about an hour using a standard TPS.

journal_name

Med Phys

journal_title

Medical physics

authors

Schulze D,Ionascu D,Tyagi N

doi

10.1118/1.4735712

subject

Has Abstract

pub_date

2012-06-01 00:00:00

pages

3849

issue

6Part20

eissn

0094-2405

issn

2473-4209

journal_volume

pub_type

杂志文章

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SU-E-T-622: A Rapid Hybrid VMAT-IMRT Planning Method Using an Abbreviated Beam Angle Optimization Search.