Impact of PET on radiation therapy planning in lung cancer

The superiority of PET imaging to structural imaging in many cancers is rapidly transforming the practice of radiotherapy planning, especially in lung cancer. Although most lung cancers are potentially treatable with radiation therapy, only patients who have truly locoregionally confined disease can be cured by this modality. PET improves selection for high-dose radiation therapy by excluding many patients who have incurable distant metastasis or extensive locoregional spread. In those patients suitable for definitive treatment, PET can help shape the treatment fields to avoid geographic miss and minimize unnecessary irradiation of normal tissues. PET will allow for more accurately targeted dose escalation studies in the future and could potentially lead to better long-term survival.

Coordinate transformations for BEAM/EGSnrc Monte Carlo dose calculations of non-coplanar fields received from a DICOM-compliant treatment planning system

The Monte Carlo (MC) method provides the most accurate to-date dose calculations in heterogeneous media and complex geometries, and this spawns increasing interest in incorporating MC calculations in the treatment planning quality assurance process. This process involves MC dose calculations for the treatment plans produced clinically. Commonly used in radiotherapy, MC codes are BEAMnrc and DOSXYZnrc, which transport particles in a coordinate system (c.s.) that has been established historically and does not correspond to the c.s. of treatment planning systems (TPSs). Relative rotations of these c.s. are not straightforward, especially for non-coplanar treatments. Transformation equations are therefore required to re-calculate a treatment plan using BEAM/DOSXYZnrc codes. This paper presents such transformations for beam angles defined in a DICOM-compliant treatment planning coordinate system. Verification of the derived transformations with two three-field plans simulated on a phantom using TPS as well as MC codes has been performed demonstrating exact geometrical agreement of the MC treatment fields' placement.