A comparison of IMRT planning systems in the treatment of colon-rectal cancer

Laub, Wolfram; Yan, Di; Sharpe, Michael B.; Nuyttens, J.; Robertson, J T; Wong, John W.

doi:10.1007/978-3-642-59758-9_198

Cited by 1 publication

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“…It has been shown that the optimization problem of the IMRT allows sufficient latitude to fine-tune the fluence distributions to increase clinical utility Nüsslin 2000, Webb et al 1998). Although these methods facilitate the translation of fluence distributions into the motion patterns of the MLC (Laub et al 2000, Mohan et al 2000, they do, in general, not ensure a feasible or the most efficient application. However, this degeneracy can be exploited to expedite the treatment delivery by stipulating a piecewise constant aperture time distribution with few discontinuities on the dose optimization problem and also to accommodate the MLC design constraints.…”

Section: Introductionmentioning

confidence: 99%

Optimization of intensity modulated radiotherapy under constraints for static and dynamic MLC delivery

Alber

Nüsslin

2001

Phys. Med. Biol.

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Multi-leaf collimators (MLCs) are emerging as the prevalent modality to apply intensity modulated radiotherapy (IMRT). Both the principle and the particular design of MLCs stipulate complex constraints on the practically applicable intensity modulated radiation fields. Most consequentially, the distribution of exposure times across the maximum field outline is either a piecewise constant function in the static mode or a piecewise linear function in the dynamic mode of driving an MLC. In view of clinical utility, the total leaf movement should be minimized, which requires that MLC-related constraints be considered in the dose optimization process. A method is proposed to achieve this for both static MLC fields and dynamic leaf close-in application. The method is an amendment to a generic gradient-based IMRT dose optimization algorithm and solves numerical problems related to the non-convexity of the MLC constraints, which can cause erratic behaviour of a gradient-based algorithm. It employs bistable penalty functions to select preferrable leaf configurations from the configuration space of the MLC, which is limited by specific design features. Together with an 'annealing' escape mechanism from local minima, the algorithm is capable of finding the optimum of an IMRT problem as leaf sequences with minimized leaf travel. In particular, the efficiency of static IMRT can be raised to the levels of unmodulated fields with very few field segments, thereby increasing the utility of IMRT in clinical practice.

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Section: Introductionmentioning

confidence: 99%