PION-Dos

PION-Dos: Patient-Specific Online-Dosimetry in Radiotherapy Using EPID

The emergence of highly conformal radiation therapies in radiooncology, like stereotactic radiation or intensity-modulated radiation therapy (IMRT) allows an optimal adaptation of the dosage distribution to the target volume, combined with simultaneous dosage reduction in normal tissue.  In this context, an accurate dosimetric quality assurance (QA) is decisive for assuring successful radiotherapeutic treatment. During the last years, numerous publications have indicated the possibility of employing EPIDs (Electronic Portal Imaging Devices) for dosage verification in conventional and IM radiation therapy.

A software prototype is to be developed which allows an online verification of the patient dose in radiotherapeutic treatment. This software prototype shall be based on an iterative reconstruction procedure yet to be developed. Using this reconstruction procedure, it will be possible to reconstruct the fluence of photons applied during treatment at the output of the linear accelerator. Furthermore, the patient dose actually applied can be calculated online while the patient is exposed to radiotherapy from the reconstructed fluence of photons, by means of a dose calculation algorithm. In order to be able to use this algorithm, one needs a cone beam CT of the patient acquired immediately before exposure, as well as the EPID scans with an indication of the gantry’s angle during radiation.