Methods for physical and radiobiological optimisation in radiotherapy with intensity modulation

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In conformal radiotherapy 'forward' treatment planning has begun to show its limitations. The resulting plan, made by 'human' optimisation, is often today no more than 'acceptable' considering the large number of possibilities given by all the new 3D-treatment options. With the introduction of Intensity Modulation (IM), it has become quite impossible to create treatment plans by forward treatment planning. For this reason, the treatment planning process has been completely changed and 'inverse' treatment planning has been introduced. The search for the optimum plan is done by a computer using human guidance rather than by human experience alone. Optimisation criteria will be introduced to guide the algorithms, implemented in inverse planning systems, to find the optimum plans. Different schools have been established proposing different optimisation criteria to realise the best clinical treatment plan, either in terms of the best 3D-dose distribution or in term of predicted tumour control and few complications in normal tissues. Many different minimisation methods, based on iterative and/or analytical techniques, have been proposed and implemented in research or commercial inverse treatment planning systems. This review aims to give a general view on these optimisation methods and criteria, including opening a window on what it is actually available commercially. A clinical example of IM application using a commercial inverse planning system on a breast tumour is described. The different sections are presented in a logical order, beginning with an introduction on optimisation definition, followed by the rationale for intensity modulation, with the third section covering the characterisation of the inverse problem in radiotherapy. The fourth section introduces the objective function, while the fifth is relative to optimizations algorithms. The final section concerns commercial inverse planning systems and includes an example of an application to a clinical case (breast tumour).

Original languageEnglish
Pages (from-to)55-73
Number of pages19
JournalPhysica Medica
Issue numberSUPPL. 2
Publication statusPublished - 2001


  • Calculation algorithms
  • Intensity modulation
  • Physics optimisation
  • Radiobiological optimisation
  • Radiotherapy
  • Treatment planning system

ASJC Scopus subject areas

  • Biophysics
  • Physics and Astronomy(all)

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