SUMMARY
Accurate tumor tracking remains a challenge in current radiation therapy. Many strategies including image guided radiation therapy alleviate the problem to certain extents. The authors propose a new modality called emission guided radiation therapy (EGRT) to accurately and directly track the tumor based on its biological signature. EGRT uses lines of response (LOR’s) from positron emission events to direct beamlets of therapeutic radiation through the emission sites inside a tumor. This is accomplished by a radiation delivery system consisting of a Linac and positron emission tomography (PET) detectors on a fast rotating closed-ring gantry. During the treatment of radiotracer-administrated cancer patients, PET detectors collect LOR’s from tumor uptake sites and the Linac responds in nearly real-time with beamlets of radiation along the same LOR paths. Moving tumors can therefore be treated with a high targeting accuracy. Based on the EGRT concept, treatment methods with dose modulation algorithms are to be designed to demonstrate the superior performance of EGRT as compared to current state-of-art conventional external beam therapy. Both simulations and patient data will be employed for demonstration of the concept and algorithms. As a new radiation therapy modality with inherent tumor tracking, EGRT has the potential to enable true biological targeting and guidance, which will substantially improve the performance of radiation therapy in the presence of intrafractional and interfractional motion.