Control of patient positioning for fast neutron therapy using positron emission tomography

Abstract

With conventional photon therapy, radiographs are widely used for the verification of patient positioning. This method cannot be used with neutrons because of the poor sensitivity of standard films to neutrons compared with γ rays. In addition, there is little difference in energy absorption between bone and soft tissue for these neutron beams (Bewley et al, 1973; Catterall & Bewley, 1979). The problem can be solved by introducing into the collimator, at the target position, a diagnostic X-ray tube (Risler & Wootton, 1988). Another approach entails visualizing the neutron-induced activity within the patient using positron emission tomography (PET). At high neutron energies, shortlived positron emitters are produced (Kleck et al, 1988; Vynckier et al, 1988) with activities sufficiently high to be visualized; the dose-equivalent rate close to the patient as a result of this activation is ∼ 30 μSv h−1 immediately after irradiation (Tatcher et al, 1987). The same approach was reported recently for pion radiotherapy (Goodman et al, 1986).

In vivoproton range verification: a review

“…The first suggestion of imaging-induced PET activity in radiotherapy was in connection with pion (Goodman et al 1986, Shirato et al 1989, neutron (Vynckier et al 1989) and heavyion therapy (Enghardt et al 1992). In the 90s, various groups (Litzenberg et al 1993, Vynckier et al 1993, Paans and Schippers 1993, Oelfke et al 1996, Litzenberg et al 1999 also started to investigate the use of PET techniques for in vivo dose monitoring of delivered proton doses.…”

Proton dose monitoring with PET: quantitative studies in Lucite

“…The visualization of induced activity patterns with a PET camera in radiotherapy has been described in previous papers for other radiation beams, i.e. for pion therapy (Goodman et al 1986, Shirato et al 1989, neutron therapy (Vynckier et al 1989, Klerck et al 1988 and heavy-ion therapy (Enghardt et al 1992, Tomitami et al 1993. Recently, various groups (Vynckier et al 1993, Paans and Schippers 1993, Litzenberg et al 1992 have started to investigate the use of PET techniques for in vivo dose monitoring of proton dose profiles.…”

Impact of the interplay between advances in imaging and radiotherapy on clinical care

“…The interest in soft-tissue tracking is also reflected in the initiatives to include MRI [88] into the IGRT process. PET-based IGRT has been suggested to offer the possibility of visualizing the dose deposition [89,90]. The online acquisition of CT images with high temporal resolution will allow for online dose reconstruction using images-of-theday and measurement of photon fluence transmitted through the patient during treatment [87].…”