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SU‐GG‐T‐117: Uniform Treatment of a Moving Target with Un‐Gated Stationary Fields
Author(s) -
Barbiere J,
Hanley J
Publication year - 2008
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2961869
Subject(s) - physics , perpendicular , radiation treatment planning , mathematics , optics , mathematical analysis , radiation therapy , geometry , medicine
Purpose: To describe the mathematical formalism necessary to compute the stationary treatment field fluence for the entire respiratory cycle that delivers a uniform dose to a moving target. Method and Materials: The desired dose D to the central plane of a moving target perpendicular to a stationary radiation beam with fluence F can be mathematically described as D = M*F where M is a binary coefficient matrix. Our algorithm computes M as function of the periodic motion and determines F by iterative gradient descent search or linear programming. The theory was tested by analyzing a model in detail and simulating the motion on a treatment planning system by shifting the beam relative to a stationary target. A clinical moving target described in the literature as suitable for gated treatment was also analyzed. The motion was divided into phases and M determined, F optimized for a single stationary field encompassing one phase near the center of the motion, and then dose to target computed. Results: We have developed a matrix mathematical formalism to compute a stationary non‐gated field fluence that can be optimized to treat a moving target and spare normal tissue. For the model case with comparable coverage using an integrated target, the use of a single field with the optimized fluence decreased the 40% normal tissue dose from 79% to 52% of the volume. The clinical target computed fluence gave a mean dose of 100% with 92.4%, 110.1%, and 5.2 as the minimum, maximum, and standard deviation respectively. Conclusion: A technique has been developed to compute the stationary treatment field fluence for the entire respiratory cycle that delivers a uniform dose to a moving target without gating. Results indicate the potential for improved normal tissue sparing while delivering a relatively uniform target dose.