Commissioning of Peacock System for intensity-modulated radiation therapy

The Peacock System was introduced to perform tomographic intensity-modulated radiation therapy (IMRT). Commissioning of the Peacock System included the alignment of the multileaf intensity-modulating collimator (MIMiC) to the beam axis, the alignment of the RTA device for immobilization, and checking the integrity of the CRANE for indexing the treatment couch. In addition, the secondary jaw settings, couch step size, and transmission through the leaves were determined. The dosimetric data required for the CORVUS planning system were divided into linear accelerator-specific and MIMiC-specific. The linear accelerator-specific dosimetric data were relative output in air, relative output in phantom, percent depth dose for a range of field sizes, and diagonal dose profiles for a large field size. The MIMiC-specific dosimetric data were the in-plane and cross-plane dose profiles of a small and a large field size to derive the penumbra fit. For each treatment unit, the Beam Utility software requires the data be entered into the CORVUS planning system in modular forms. These modules were treatment unit information, angle definition, configuration, gantry and couch angles range, dosimetry, results, and verification plans. After the appropriate machine data were entered, CORVUS created a dose model. The dose model was used to create known simple dose distribution for evaluation using the verification tools of the CORVUS. The planned doses for phantoms were confirmed using an ion chamber for point dose measurement and film for relative dose measurement. The planning system calibration factor was initially set at 1.0 and will be changed after data on clinical cases are acquired. The treatment unit was released for clinical use after the approval icon was checked in the verification plans module.