Abstract

Purpose/Objective (s): Ability of on-line adaptive re-planning is desirable to correct for inter-fraction anatomic changes. A fullscope re-planning/re-optimization with the current planning techniques takes too long to be practical. The purpose of this work is to develop a scheme that may be implemented as an on-line re-planning strategy to correct for inter-fraction anatomic changes.
Method/Materials: The scheme consists of three steps:(1) rapidly delineating targets and organs at risk (OAR) on the CT of the day by modifying original planning contours using a robust tool in a semi-automatic manner,(2) adjusting (morphing) beam/segment apertures based on differences between planning contours and new contours, and (3) optimizing weights of the new apertures if necessary. The aperture morphing is accomplished by applying the spatial relationship between the planning target contour and the apertures to the new target contour. The dose distribution for each new aperture was generated using a planning system equipped with a fast dose engine and hardware (Prowess), and was input into a newly-developed package for weight optimization using a fast sequential quadratic programming to achieve uniform target dose with constraints for OARs. The obtained new aperture weights were transferred into the planning system to generate a new deliverable plan. The entire scheme was tested for direct-aperture-based IMRT on representative prostate and uterus cases where daily CT images was acquired using an in-room CT (Siemens).
Results: Figure below compares the prostate PTV and rectal DVHs generated based on the CT of the day for 5 …

Date

2007

Authors

E Ahunbay, G Chen, C Peng, CX Yu, S Narayanan, XA Li

Journal

International Journal of Radiation Oncology, Biology, Physics

Volume

69

Issue

3

Pages

S23

Publisher

Elsevier