Measurement of characteristic prompt gamma rays emitted from oxygen and carbon in tissue-equivalent samples during proton beam irradiation

Abstract

The purpose of this work was to characterize how prompt gamma (PG) emission from tissue changes as a function of carbon and oxygen concentration, and to assess the feasibility of determining elemental concentration in tissues irradiated with proton beams. For this study, four tissue-equivalent water-sucrose samples with differing densities and concentrations of carbon, hydrogen, and oxygen were irradiated with a 48 MeV proton pencil beam. The PG spectrum emitted from each sample was measured using a high-purity germanium detector, and the absolute detection efficiency of the detector, average beam current, and delivered dose distribution were also measured. Changes to the total PG emission from 12C (4.44 MeV) and 16O (6.13 MeV) per incident proton and per Gray of absorbed dose were characterized as a function of carbon and oxygen concentration in the sample. The intensity of the 4.44 MeV PG emission per incident proton was found to be nearly constant for all samples regardless of their carbon concentration. However, we found that the 6.13 MeV PG emission increased linearly with the total amount (in grams) of oxygen irradiated in the sample. From the measured PG data, we determined that 1.64 × 107 oxygen PGs were emitted per gram of oxygen irradiated per Gray of absorbed dose delivered with a 48 MeV proton beam. These results indicate that the 6.13 MeV PG emission from 16O is proportional to the concentration of oxygen in tissue irradiated with proton beams, showing that it is possible to determine the concentration of oxygen within tissues irradiated with proton beams by measuring 16O PG emission.

Pixelated prompt gamma imaging detector for online measurement of proton beam: Monte Carlo feasibility study by FLUKA

“…The photon energy spectrum has a continuous component decreasing above 7 MeV and neutrons decreasing strongly above 100 MeV. The high-energy gamma rays are listed by Kozlovsky et al [6] and Polf [7] The distal end of gamma distribution and the Bragg peak in the PMMA target are at the same depth; as shown in Fig. 3, the deposited energy with Bragg peak of the 160 MeV proton beam is plotted in black square and gamma distribution in green circle.…”

Nuclear physics and particle therapy

“…The photon spectrum presents a continuum component and several de-excitation lines. Such lines have different intensities depending on the traversed tissue, thus allowing for the determination of its composition, in particular the oxygen concentration [70]. As an example, Figure 13 shows the Figure 13.…”

Imaging particle beams for cancer treatment

“…Initial studies have found a good correlation between dose delivery and prompt-gamma emission, 9,10 and small shifts in the Bragg peak position can be detected by measuring prompt-gamma emission during treatment. 11,12 Recent studies have also shown that the intensities of the characteristic prompt-gamma spectral lines from individual elements are directly proportional to the concentration of the elements in tissue, 13 so prompt-gamma imaging could provide a path to spectroscopic analysis of irradiated tumors and healthy tissues.…”