@article{oai:repo.qst.go.jp:00080143,
 author = {Chacon, Andrew and James, Benjamin and Linh Tran, Thuy and Guatelli, Susanna and Chartier, Lachlan and Prokopvich, Dale and R. Franklin, Daniel and Mohammadi, Akram and Nishikido, Fumihiko and Iwao, Yuma and Akamatsu, Go and Takyu, Sodai and Tashima, Hideaki and Yamaya, Taiga and Parodi, Katia and Rosenfeld, Anatoly and Mitra, Safavi‐Naeini and Linh Tran, Thuy and Lachlan, Chartier and Mohammadi, Akram and Fumihiko, Nishikido and Yuma, Iwao and Go, Akamatsu and Sodai, Takyu and Hideaki, Tashima and Taiga, Yamaya and Parodi, Katia},
 issue = {7},
 journal = {Medical Physics},
 month = {May},
 note = {Purpose
This work has two related objectives. The first is to estimate the relative biological effectiveness of two radioactive heavy ion beams based on experimental measurements, and compare these to the relative biological effectiveness of corresponding stable isotopes to determine whether they are therapeutically equivalent. The second aim is to quantitatively compare the quality of images acquired postirradiation using an in‐beam whole‐body positron emission tomography scanner for range verification quality assurance.

Methods
The energy deposited by monoenergetic beams of urn:x-wiley:00942405:media:mp14177:mp14177-math-0001C at 350 MeV/u, urn:x-wiley:00942405:media:mp14177:mp14177-math-0002O at 250 MeV/u, urn:x-wiley:00942405:media:mp14177:mp14177-math-0003C at 350 MeV/u, and urn:x-wiley:00942405:media:mp14177:mp14177-math-0004O at 430 MeV/u was measured using a cruciform transmission ionization chamber in a water phantom at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. Dose‐mean lineal energy was measured at various depths along the path of each beam in a water phantom using a silicon‐on‐insulator mushroom microdosimeter. Using the modified microdosimetric kinetic model, the relative biological effectiveness at 10% survival fraction of the radioactive ion beams was evaluated and compared to that of the corresponding stable ions along the path of the beam. Finally, the postirradiation distributions of positron annihilations resulting from the decay of positron‐emitting nuclei were measured for each beam in a gelatin phantom using the in‐beam whole‐body positron emission tomography scanner at HIMAC. The depth of maximum positron‐annihilation density was compared with the depth of maximum dose deposition and the signal‐to‐background ratios were calculated and compared for images acquired over 5 and 20 min postirradiation of the phantom.

Results
In the entrance region, the urn:x-wiley:00942405:media:mp14177:mp14177-math-0005 was 1.2 ± 0.1 for both urn:x-wiley:00942405:media:mp14177:mp14177-math-0006C and urn:x-wiley:00942405:media:mp14177:mp14177-math-0007C beams, while for urn:x-wiley:00942405:media:mp14177:mp14177-math-0008O and urn:x-wiley:00942405:media:mp14177:mp14177-math-0009O it was 1.4 ± 0.1 and 1.3 ± 0.1, respectively. At the Bragg peak, the urn:x-wiley:00942405:media:mp14177:mp14177-math-0010 was 2.7 ± 0.4 for urn:x-wiley:00942405:media:mp14177:mp14177-math-0011C and 2.9 ± 0.4 for urn:x-wiley:00942405:media:mp14177:mp14177-math-0012C, while for urn:x-wiley:00942405:media:mp14177:mp14177-math-0013O and urn:x-wiley:00942405:media:mp14177:mp14177-math-0014O it was 2.7 ± 0.4 and 2.8 ± 0.4, respectively. In the tail region, urn:x-wiley:00942405:media:mp14177:mp14177-math-0015 could only be evaluated for carbon; the urn:x-wiley:00942405:media:mp14177:mp14177-math-0016 was 1.6 ± 0.2 and 1.5 ± 0.1 for urn:x-wiley:00942405:media:mp14177:mp14177-math-0017C and urn:x-wiley:00942405:media:mp14177:mp14177-math-0018C, respectively. Positron emission tomography images obtained from gelatin targets irradiated by radioactive ion beams exhibit markedly improved signal‐to‐background ratios compared to those obtained from targets irradiated by nonradioactive ion beams, with 5‐fold and 11‐fold increases in the ratios calculated for the urn:x-wiley:00942405:media:mp14177:mp14177-math-0019O and urn:x-wiley:00942405:media:mp14177:mp14177-math-0020C images compared with the values obtained for urn:x-wiley:00942405:media:mp14177:mp14177-math-0021O and urn:x-wiley:00942405:media:mp14177:mp14177-math-0022C, respectively. The difference between the depth of maximum dose and the depth of maximum positron annihilation density is 2.4 ± 0.8 mm for urn:x-wiley:00942405:media:mp14177:mp14177-math-0023C, compared to −5.6 ± 0.8 mm for urn:x-wiley:00942405:media:mp14177:mp14177-math-0024C and 0.9 ± 0.8 mm for urn:x-wiley:00942405:media:mp14177:mp14177-math-0025O vs −6.6 ± 0.8 mm for urn:x-wiley:00942405:media:mp14177:mp14177-math-0026O.

Conclusions
The urn:x-wiley:00942405:media:mp14177:mp14177-math-0027 values for urn:x-wiley:00942405:media:mp14177:mp14177-math-0028C and urn:x-wiley:00942405:media:mp14177:mp14177-math-0029O were found to be within the 95% confidence interval of the RBEs estimated for their corresponding stable isotopes across each of the regions in which it was evaluated. Furthermore, for a given dose, urn:x-wiley:00942405:media:mp14177:mp14177-math-0030C and urn:x-wiley:00942405:media:mp14177:mp14177-math-0031O beams produce much better quality images for range verification compared with urn:x-wiley:00942405:media:mp14177:mp14177-math-0032C and urn:x-wiley:00942405:media:mp14177:mp14177-math-0033O, in particular with regard to estimating the location of the Bragg peak.},
 pages = {3123--3132},
 title = {Experimental investigation of the characteristics of radioactive beams for heavy ion therapy},
 volume = {47},
 year = {2020}
}