Approximated segmentation considering technical and dosimetric constraints in intensity-modulated radiation therapy with electrons

TL;DR

This paper introduces heuristic algorithms for segmenting intensity maps in electron-based radiation therapy, optimizing dose delivery by reducing segments and monitor units while respecting dosimetric constraints.

Contribution

It presents novel heuristic segmentation algorithms that improve dose delivery efficiency in intensity-modulated radiation therapy with electrons.

Findings

Fewer segments achieved with dosimetric constraints

Significant reduction in monitor units

More efficient and faster dose delivery

Abstract

In intensity-modulated radiation therapy, optimal intensity distributions of incoming beams are decomposed into linear combinations of leaf openings of a multileaf collimator (segments). In order to avoid inefficient dose delivery, the decomposition should satisfy a number of dosimetric constraints due to suboptimal dose characteristics of small segments. However, exact decomposition with dosimetric constraints is only in limited cases possible. The present work introduces new heuristic segmentation algorithms for the following optimization problem: Find a segmentation of an approximated matrix using only allowed fields and minimize the approximation error. Finally, the decomposition algorithms were implemented into an optimization programme in order to examine the assumptions of the algorithms for a clinical example. As a result, identical dose distributions with much fewer segments and a significantly smaller number of monitor units could be achieved using dosimetric constraints. Consequently, the dose delivery is more efficient and less time consuming.