Production yields of 𝛽⁺ emitters for range verification in proton therapy

¹ Dept. de Física Atómica, Molecular y Nuclear. Universidad de Sevilla. Avda. Reina Mercedes, s/n, 41012, Sevilla, Spain
² Centro Nacional de Aceleradores (Universidad de Sevilla, Junta de Andalucía, CSIC). C/ Thomas Alva Edison, 41092. Sevilla, Spain
³ KVI-Center for Advanced Radiation Technology. University of Groningen. Zernikelaan 25, 9747, Groningen, The Netherlands
⁴ Grupo de Física Nuclear and Iparcos, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, CEI Moncloa, Madrid 28040, Spain

^* e-mail: mrodriguezg@us.es
^** e-mail: cguerrero4@us.es

Published online: 30 September 2020

Abstract

In-vivo Positron Emission Tomography (PET) range verification relies on the comparison of the measured and estimated activity distributions from β⁺ emitters induced by the proton beam on the most abundant elements in the human body, right after (looking at the long-lived β⁺ emitters ¹¹C, ¹³N and ¹⁵O) or during (looking at the short-lived β⁺ emitters ²⁹P, ¹²N, ^38mK and ¹⁰C) the irradiation. The accuracy of the estimated activity distributions is basically that of the underlying cross section data. In this context, the aim of this work is to improve the knowledge of the production yields of β⁺ emitters of interest in proton therapy. In order to measure the long-lived β⁺ isotopes, a new method has been developed combining the multi-foil technique with the measurement of the induced activity with a clinical PET scanner. This technique has been tested successfully below 18 MeV at CNA (Spain) and will be used at a clinical beam to obtain data up to 230 MeV. However, such method does not allow measuring the production short-lived isotopes (lower half-life). For this, the proposed method combines a series of targets sandwiched between aluminum foils (acting as both degraders and converters) placed between two LaBr₃ detectors that will measure the pairs of 511 keV γ-rays. The first tests will take place at the AGOR facility at KVI-CART, in Groningen.