Browsing by Author "James, B"

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    3D sensitive volume microdosimeter with improved tissue equivalency: charge collection study and its application in 12C ion therapy
    (IOP Publishing, 2018-02-06) James, B; Tran, LT; Bolst, D; Prokopovich, DA; Reinhard, MI; Lerch, MLF; Petasecca, M; Guatelli, S; Povoli, M; Kok, A; Matsufuji, N; Jackson, M; Rosenfeld, AB
    This research focuses on the characterisation of a new 3D sensitive volume (SV) microdosimeter covered with polyimide – a material which closely mimics human tissue. The electrical and charge collection properties of the device were investigated and its application in 12C ion therapy were studied. Charge collection studies revealed uniform charge collection and no cross talk between adjacent SVs. To study the microdosimetric response in 12C ion therapy, the new polyimide mushroom microdosimeter were placed at various positions along the central axis of a 290 MeV/u 12C ion spread out Bragg peak (SOBP) at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. From these microdosimetric spectra, dose mean lineal energy $(\overline{{y}_{D})}$ and RBE10 results were obtained, with RBE10 increasing from 1.3 at the entrance to 2.7 at the end of the SOBP. The results obtained in this work show that the new generation of mushroom microdosimeters, covered with tissue equivalent polyimide material, are a useful tool for quality assurance in heavy ion therapy applications. © Open Access - CC BY - IOP Publishing Ltd.
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    Experimental investigation of the characteristics of radioactive beams for heavy ion therapy
    (Wiley, 2020-07) Chacon, A; James, B; Tran, LT; Guatelli, S; Chartier, L; Prokopvich, DA; Franklin, DR; Mohammadi, A; Nishikido, F; Iwao, Y; Akamatsu, G; Takyu, S; Tashima, H; Yamaya, T; Parodi, K; Rosenfeld, AB; Safavi‐Naeini, M
    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 C at 350 MeV/u, O at 250 MeV/u, C at 350 MeV/u, and O 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 was 1.2 ± 0.1 for both C and C beams, while for O and O it was 1.4 ± 0.1 and 1.3 ± 0.1, respectively. At the Bragg peak, the was 2.7 ± 0.4 for C and 2.9 ± 0.4 for C, while for O and O it was 2.7 ± 0.4 and 2.8 ± 0.4, respectively. In the tail region, could only be evaluated for carbon; the was 1.6 ± 0.2 and 1.5 ± 0.1 for C and C, 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 O and C images compared with the values obtained for O and C, respectively. The difference between the depth of maximum dose and the depth of maximum positron annihilation density is 2.4 ± 0.8 mm for C, compared to −5.6 ± 0.8 mm for C and 0.9 ± 0.8 mm for O vs −6.6 ± 0.8 mm for O. Conclusions The values for C and O 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, C and O beams produce much better quality images for range verification compared with C and O, in particular with regard to estimating the location of the Bragg peak. © 2024 American Association of Physicists in Medicine.
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    IBIC microscopy – the powerful tool for testing micron – sized sensitive volumes in segmented radiation detectors used in synchrotron microbeam radiation and hadron therapies
    (Elsevier B. V., 2019-11-01) Pastuovic, Z; Davis, J; Tran, LT; Paino, JR; Dipuglia, A; James, B; Povoli, M; Kok, A; Perevertaylo, VL; Siegele, R; Prokopovich, DA; Lerch, MLF; Petasecca, M; Rosenfeld, AB; Cohen, DD
    Ion Beam Induced Charge (IBIC) microscopy performed using highly tuned microbeams of accelerated ions with energies in the MeV range is the powerful tool for analysis of charge carrier transport properties in semiconductor devices based on semiconductor hetero-junction, metal-on-semiconductor and semiconductor-on-insulator configurations. Here we present two cases of recent applications of the IBIC microscopy in the field of medical radiation physics. The reduced-rate ion microbeams with energies in the MeV range and sub-micrometer spot-sizes have been used for the investigations of the charge collection efficiency (CCE) in sensitive volumes of segmented radiation detectors in order to measure the spatial distribution and uniformity of CCE in different polarization conditions. This information allows the determination of the charge carrier transport properties in selected substructures of a particular device and to quantify its ability to accurately determine the energy deposited by incident ionizing radiation - two fundamental requirements of any microdosimeter or detector of ionizing radiation. © 2019 Elsevier B.V.