Interplay effects during enhanced dynamic wedge deliveries

Abstract In this study the interplay effects for Enhanced Dynamic Wedge (EDW) treatments are experimentally investigated. Single and multiple field EDW plans for different wedge angles were delivered to a phantom and detector on a moving platform, with various periods, amplitudes for parallel and pe...

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Bibliographic Details
Published in:Physica medica 2013-06, Vol.29 (4), p.323-332
Main Authors: Kakakhel, M.B, Kairn, T, Kenny, J, Seet, K, Fielding, A.L, Trapp, J.V
Format: Article
Language:English
Subjects:
Dynamic wedges
Four-Dimensional Computed Tomography
Fractionated delivery
Humans
Interplay effects
Motion
Movement
Phantoms, Imaging
Radiology
Radiotherapy Planning, Computer-Assisted
Radiotherapy, Computer-Assisted - instrumentation
Radiotherapy, Computer-Assisted - methods
Tumor motion
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Summary:Abstract In this study the interplay effects for Enhanced Dynamic Wedge (EDW) treatments are experimentally investigated. Single and multiple field EDW plans for different wedge angles were delivered to a phantom and detector on a moving platform, with various periods, amplitudes for parallel and perpendicular motions. A four field 4D CT planned lung EDW treatment was delivered to a dummy tumor over four fractions. For the single field parallel case the amplitude and the period of motion both affect the interplay resulting in the appearance of a step function and penumbral cut off with the discrepancy worst where collimator-tumor speed is similar. For perpendicular motion the amplitude of tumor motion is the only dominant factor. For large wedge angle the dose discrepancy is more pronounced compared to the small wedge angle for the same field size and amplitude-period values. For a small field size i.e. 5 × 5 cm2 the loss of wedged distribution was observed for both 60° and 15° wedge angles for parallel and perpendicular motions. Film results from 4D CT planned delivery displayed a mix of over and under dosages over 4 fractions, with the gamma pass rate of 40% for the averaged film image at 3%/1 mm DTA (Distance to Agreement). Amplitude and period of the tumor motion both affect the interplay for single and multi-field EDW treatments and for a limited (4 or 5) fraction delivery there is a possibility of non-averaging of the EDW interplay.
ISSN:1120-1797
1724-191X
DOI:10.1016/j.ejmp.2012.04.007