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.
Highlights
In comparison to conventional radiation therapy, proton therapy is able to reduce the radiation dose deposition in the healthy tissues adjacent to the tumor
The spatial dose distribution of the protons is characterized by its maximum dose deposition near the end of the trajectory, the Bragg peak, and its finite penetration in the patient, making proton therapy especially well-suited for tumor close to organs at risk and in pediatric cancers
A possibility to verify the range of the proton beam is to use Positron Emission Tomography (PET) to look at the β+ emitters produced in the body of the patient during the irradiation
Summary
In comparison to conventional radiation therapy, proton therapy is able to reduce the radiation dose deposition in the healthy tissues adjacent to the tumor. The spatial dose distribution of the protons is characterized by its maximum dose deposition near the end of the trajectory, the Bragg peak, and its finite penetration in the patient, making proton therapy especially well-suited for tumor close to organs at risk and in pediatric cancers. Current treatment plannings have to consider safety margins associated to the uncertainty in the actual beam range in the patient, limiting the potential benefits of proton therapy. For this reason, it is highly desirable to verify the particle beam range directly in-vivo. The threshold energies to produce β+ emitters cause the activity to drop about
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