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A fast 4D IMRT/VMAT planning method based on segment aperture morphing. Med Phys 2018 Apr;45(4):1594-1602



Pubmed ID




Scopus ID

2-s2.0-85042275205   1 Citation


PURPOSE: Four-dimensional volumetric modulated arc therapy (4D VMAT) and four-dimensional intensity-modulated radiotherapy (4D IMRT) are developing radiation therapy treatment strategies designed to maximize dose conformality, minimize normal tissue dose, and deliver the treatment as efficiently as possible. The patient's entire breathing cycle is captured through 4D imaging modalities and then separated into individual breathing phases for planning purposes. Optimizing multiphase VMAT and IMRT plans is computationally demanding and currently impractical for clinical application. The purpose of this study is to assess a new planning process decreasing the upfront computational time required to optimize multiphased treatment plans while maintaining good plan quality.

METHODS: Optimized VMAT and IMRT plans were created on the end-of-exhale (EOE) breathing phase of 10-phase 4D CT scans with planning tumor volume (PTV)-based targets. These single-phase optimized plans are analogous to single-phase gated treatment plans. The simulated tracked plans were created by deformably registering EOE contours to the remaining breathing phases, recalculating the optimized EOE plan onto the other individual phases and realigning the MLC's relative positions to the PTV border in each of the individual breathing phases using a segment aperture morphing (SAM) algorithm. Doses for each of the 10 phases were calculated with the treatment planning system and deformably transferred back onto the EOE phase and averaged with equal weighting simulating the actual delivered dose a patient would potentially receive in a tracked treatment plan.

RESULTS: Plan DVH quality for the 10-phase 4D SAM plans were comparable with the individual EOE optimized treatment plans for the PTV structures as well as the organ at risk structures. SAM-based algorithms out performed simpler isocenter-shifted only approaches. SAM-based 4D planning greatly reduced plan computation time vs individually optimizing all 10 phases. In addition, since this technique allows irradiation during all 10 breathing phases it will also decrease the treatment times required to treat each fraction in comparison to the gated treatment planning approach.

CONCLUSIONS: Segment aperture morphing (SAM) can successfully be used to transfer radiation therapy plans originally planned on a single breathing phase image set to other patient breathing phase image sets. SAM is a useful tool for the fast creation of 4D, multibreathing phase radiation therapy treatment plans.

Author List

Klawikowski S, Tai A, Ates O, Ahunbay E, Li XA


Ergun Ahunbay PhD Associate Professor in the Radiation Oncology department at Medical College of Wisconsin
Slade J. Klawikowski PhD Instructor in the Radiation Oncology department at Medical College of Wisconsin
X Allen Li PhD Professor in the Radiation Oncology department at Medical College of Wisconsin
An Tai PhD Associate Professor in the Radiation Oncology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Four-Dimensional Computed Tomography
Image Processing, Computer-Assisted
Lung Neoplasms
Organs at Risk
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Radiotherapy, Intensity-Modulated
Time Factors
jenkins-FCD Prod-480 9a4deaf152b0b06dd18151814fff2e18f6c05280