The rapid fall-off of dose at the end of range of proton beams has the potential of sparing critical structures just distal to the target volume. This tremendous advantage of protons is, however, not always used to its full extent, because treatment planning and delivery in proton radiotherapy often implies unpredictable uncertainties. The most promising method for an in vivo and noninvasive monitoring of proton radiotherapy is positron emission tomography (PET). Positron emitters such as 11C and 15O are produced via nuclear interactions along the proton beam path, and can be imaged as a spatial marker of dose deposition. This way PET/CT imaging can be employed as a quality ssurance tool, to verify the actually delivered dose, and to quantify uncertainties. In this thesis we investigate the physical and clinical potential of offline PET/CT imaging for proton treatment verification. In a phantom study we determine the physical reproducibility, consistency, and sensitivity of the approach. The presented patient study qualitatively and quantitatively evaluates its clinical performance. Data of 23 patients (9 patient data sets were acquired before, 14 within the framework of this work) with various tumor sites are analyzed. The influence of different challenging factors is studied with respect to different tumor locations. This way patient subgroups that benefit most from the approach are determined. Furthermore, possible technological and methodological improvements to allow for a wider applicability of PET/CT treatment verification are identified.
|Qualification||Doctor of Philosophy|
|Publication status||Published - 2009|