Production of clinically useful positron emitter beams during carbon ion deceleration

Abstract

In external beam radiation therapy, radioactive beams offer the best clinical solution to simultaneously treat and in vivo monitor the dose delivery and tumor response using PET or PET-CT imaging. However, difficulties mainly linked to the low production efficiency have so far limited their use. This study is devoted to the analysis of the production of high energy (11)C fragments, preferably by projectile fragmentation of a stable monodirectional and monoenergetic primary (12)C beam in different absorbing materials (decelerators) in order to identify the optimal elemental composition. The study was performed using the Monte Carlo code SHIELD-HIT07. The track length and fluence of generated secondary particles were scored in a uniform absorber of 300 cm length and 10 cm radius, divided into slices of 1 cm thickness. The (11)C fluence build-up and mean energy variation with increasing decelerator depth are presented. Furthermore, the fluence of the secondary (11)C beam was studied as a function of its mean energy and the corresponding remaining range in water. It is shown that the maximum (11)C fluence build-up is high in compounds where the fraction by weight of hydrogen is high, being the highest in liquid hydrogen. Furthermore, a cost effective alternative solution to the single medium initially envisaged is presented: a two-media decelerator that comprises a first liquid hydrogen section followed by a second decelerating section made of a hydrogen-rich material, such as polyethylene (C(2)H(4)). The purpose of the first section is to achieve a fast initial (11)C fluence build-up, while the second section is primarily designed to modulate the mean energy of the generated (11)C beam in order to reach the tumor depth. Finally, it was demonstrated that, if the intensity of the primary (12)C beam can be increased by an order of magnitude, a sufficient intensity of the secondary (11)C beam is achieved for therapy and subsequent therapeutic PET imaging sessions. Such an increase in the intensity might be easily achieved with a superconducting cyclotron.

A Monte Carlo evaluation of carbon and lithium ions dose distributions in water

“…The general purpose Monte Carlo codes, SHIELD-HIT10 (Heavy Ion Transport) (Gudowska et al 2004, Geithner et al 2006, Sobolevsky 2010 and FLUKA 2008.3d.1 (FLUKtuierende KAskade) (Ferrari et al 2005, are capable of performing heavy ion transport in heterogeneous complex geometries. SHIELD-HIT has been used in several studies of relevance to radiotherapy with light ions, e.g., in the evaluation of secondary organ absorbed doses from irradiation with primary beams of protons up to oxygen ions , and studies of the production of clinically useful positron emitter beams during carbon ion deceleration (Lazzeroni and Brahme 2011). Similarly, the FLUKA code 190 R. Taleei et al has been used in radiotherapy studies such as calculations of physical and biological doses for hadron therapy (Battistoni et al 2008).…”

Evaluation of nuclear reaction cross-sections and fragment yields in carbon beams using the SHIELD-HIT Monte Carlo code. Comparison with experiments

“…Total inelastic cross-sections employed in SHIELD-HIT for 12 C projectile on H and C target nuclei have been presented by Lazzeroni and Brahme (2011). These cross-sections showed rather good agreement with measurements in the whole energy range covered by the experimental data, particularly in the proton-nucleus case.…”

“…In SHIELD-HIT, inelastic nuclear reactions are modeled by the Many Stage Dynamical Model (MSDM) which assumes the following sequential stages of the interaction process: fast cascade, coalescence, pre-equilibrium decay of residual nuclei, and equilibrated de-excitation of the residual nucleus (Botvina et al 1987(Botvina et al , 1997. The SHIELD-HIT code has been used in several studies of relevance in radiotherapy with light ions (Geithner et al 2006, Kempe et al 2007, Hollmark et al 2008, Kempe and Brahme 2010, Hultqvist and Gudowska 2010, Lazzeroni and Brahme 2011. The benchmarking of SHIELD-HIT includes the simulation of absorbed dose delivered to water for projectiles of 1 H and 12 C ions with energies 100-400 MeV u −1 , total reaction cross-sections for protons on various target materials (Gudowska et al 2004, Gudowska and, fragment yields in water for a 290 MeV u −1 12 C beam and fragment fluences differential in energy for a 200 MeV u −1 12 C beam (Geithner et al 2006), neutron production in light media from irradiation with 177.5 MeV u −1 4 He ions (Gudowska et al 2007) and absorbed dose in water for 185 MeV u −1 7 Li ions and 300 MeV u −1 12 C ions (Taleei et al 2011).…”

A simulation study of a dual-plate in-room PET system for dose verification in carbon ion therapy

“…Considering the above situation, a tool that can monitor the treatment dose distribution in vivo and non-invasively is required. A positron emission tomography (PET) scanner is a feasible solution for this purpose because it can image the 3D distribution of positron emitters produced by nuclear fragmentation reactions of the projectiles with target nu-clei [2,3].…”