A direct profile measurement of 11C positron activation of carbon-rich materials by therapeutic proton beam

Radiation therapy with hadrons, especially protons is becoming a mainstream modality with its annual clinical use already measured by multiple thousands of patient treatments worldwide. Advanced treatment planning allows optimization of dose delivery by spreading the Bragg peak over tumor size. The advent of pencil-beam rastering can further improve tumor-to-normal-tissue dose ratio. Positron Emission Tomography has a great potential as dose delivery monitoring technique, verifying that the actual dose distribution matches the treatment plan. In order to fully realize this potential, the positron activation profiles in the human tissues must be known with a good precision. The results of a conceptually simple and yet fairly accurate ¹¹C activation profile measurement in two different carbon-rich media are presented. The ¹¹C carbon activation many centimeters beyond the Bragg peak was also characterized.