Conformity of brain lesions treated with radiosurgery and fractionated stereotactic radiotherapy
The quality of radiosurgery and fractionated stereotactic radiotherapy treatments of brain lesions performed during 2008 at IPOCFG, E.P.E., Coimbra, Portugal is assessed in terms of dose-volume indexes, namely the conformity index. The irradiation technique is based on a micromultileaf collimator with dynamic conformal arcs for radiosurgery and multiple conformal beams for fractionated stereotactic radiotherapy. The dependence of the conformity index with the resolution of the calculation grid is discussed. For fractionated stereotactic radiotherapy the critical organs near the target are taken into account in the definition of the conformity index and the penalties resulting from this inclusion are discussed. The local clinical acceptance criteria in terms of coverage and conformity are also presented. The coverage criteria of 95% has been always accomplished and well surpassed. For radiosurgery treatments the average conformity index was 0.593±0.071 whereas for fractionated stereotactic radiotherapy it was 0.584±0.094 with a loss of 9.2%, on average, if the penalty factors for the critical organs are taken into account.
Keywordsradiosurgery fractionated stereotactic radiotherapy conformity index coverage index
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