Production yields at the distal fall-off of the β+ emitters 11C and 13N for in-vivo range verification in proton therapy

Abstract

In proton therapy, Positron Emission Tomography (PET) range verification relies on the comparison of the measured and estimated activity distributions from β+ emitters produced by the proton beam in the patient. The accuracy of the estimated activity distributions is basically that of the underlying reaction cross section data. In this context, we have developed a new method for measuring β+ production yields combining the multi-foil technique with a clinical PET scanner, resulting in energy differential cross sections from a single irradiation. The method has been applied to the production of (t1/2 = 20.36 min) and (t1/2 = 9.97 min), the main candidates for off-line PET range verification, in carbon, nitrogen and oxygen, the main elements of the human body. The energy range studied with the 18 MeV CNA cyclotron corresponds to the distal fall-off of the activity curve, i.e. near the Bragg peak.