Range verification of radioactive ion beams of ¹¹C and ¹⁵O using in-beam PET imaging

Abstract

In advanced ion therapy, the visualization of the range of incident ions in a patient's body is important for exploiting the advantages of this type of therapy. It is ideal to use radioactive ion beams for in-beam positron emission tomography (PET) imaging in particle therapy due to the high quality of PET images caused by the high signal-to-noise ratio. We have shown the feasibility of this idea through an in-beam PET study for 11 C and 15 O ion beams using the dedicated OpenPET system. In this work, we investigate the potential difference between the Bragg peak position and the position of the maximum detected positron-emitting fragments by a PET system for the radioactive beams of 11 C and 15 O. For this purpose, we measured the depth dose in a water phantom and performed PET scans of an irradiated PMMA phantom for the available beams of 11 C and 15 O at the Heavy Ion Medical Accelerator in Chiba (HIMAC). Then, we simulated the depth dose profiles in the water phantom and the yield of the positron-emitting fragments in a PMMA phantom for both available beams using the Monte Carlo code PHITS. The positions of the Bragg peak and maximum positronemitting fragments from the measurements were well reproduced by simulation. The effect of beam energy broadening on the positional differences between two peaks was studied by simulating an irradiated PMMA phantom. The differences in position between the Bragg peak and the maximum positron-emitting fragments increased when the beam energy spread was broadened, although the differences were zero for the ideal mono-energetic beams. Greater differences were observed for 11 C ion beams compared to 15 O ion beams, although both beams had the same range in water, and the higher energy corresponded to a larger difference. For the known energy spread of the beams, the predicted differences between two peaks from the simulation were consistent with the measured data within submillimetre agreement.

Immuno-OpenPET: a novel approach for early diagnosis and image-guided surgery for small resectable pancreatic cancer

“…S6 and S7. ion therapy 32 . Additionally, in a recent multi-institutional clinical study, carbon ion therapy showed favorable outcomes with limited toxicities for PC treatment 33 .…”

Radioactive Beams in Particle Therapy: Past, Present, and Future

“…An additional problem in the in-flight technique is the large momentum spread. This spread causes a shift between the Bragg peak and activity peak for RIB [83]. Even if this shift is smaller than the one observed using stable ions for treatment and projectile fragments for PET imaging (Figure 2), it increases with the momentum acceptance.…”

Development of a Multiuse Human-Scale Single-Ring OpenPET System

“…Because of the wide-open space and mobility, the system can be used to study the washout effect using animals [50][51][52][53][54]. It has been suggested that radioactive ion beams are useful for washout studies [55][56][57][58]. Therefore, our future work with the developed system will include a washout study with radioactive ion beams and entire-body scanning of animals.…”