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

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.

In-Beam PET And Compton Imaging For Enhanced Accuracy Proton-Range Verification

“…1. This configuration was chosen for a twofold study, on the one hand, to measure proton-induced β + -emitter production cross sections 23 and, on the other hand, to explore the combination of Compton and PET imaging for ion-range verification, which is the main objective of this article. The proton beam direction is indicated by the red arrow.…”

“…A sample holder (elongated U-shaped piece in the center) was used to simultaneously expose regularly spaced thin sample-foils to the proton-beam. Both the holder and the samples themselves were specifically designed for a parallel study devoted to the determination of production cross sections of β + emitting isotopes 23,24 . However, as discussed later, this set-up turned out to be very well suited for the simultaneous demonstration of PET and Compton imaging discussed in this work.…”