Secondary Radiation in Ion Therapy and Theranostics: A Review

Abstract

Ion therapy has emerged as one of the preferred treatment procedures in some selective indication of cancer. The actual dose delivered to the target volume may differ from the planned dose due to wrong positioning of the patient and organ movement during beam delivery. On the other hand, some healthy tissues outside the planned volume may be exposed to radiation dose. It is necessary to determine the primary particle range and the actual exposed volume during irradiation. Many proposed techniques use secondary radiation for the purpose. The secondary radiation consists mainly of neutrons, charged fragments, annihilation photons, among others, and prompt gammas. These are produced through nuclear interaction of the primary beam with the beam line and the patient’s body tissue. Besides its usefulness in characterizing the primary beam, the secondary radiation contributes to the risk of exposure of different tissues. Secondary radiation has significant contribution in theranostics, a comparatively new branch of medicine, which combines diagnosis and therapy. Many authors have made detailed study of the dose delivered to the patient by the secondary radiation and its effects. They have also studied the correlation of secondary charged particles with the beam range and the delivered dose. While these studies have been carried out in great detail in the case of proton and carbon therapy, there are fewer analyses for theranostics. In the present review, a brief account of the studies carried out so far on secondary radiation in ion therapy, its effect, and the role of nuclear reactions is given.

Particle Therapy: Clinical Applications and Biological Effects

“…Ion-induced ultrasound, MRI, Positron Emission Tomography and Interaction Vertex Imaging are used for imaging based on secondary radiation generation. In 2003, Stichelbaut and Jongen proposed the use of rapid gamma-ray detection (PG), and evidence for the use of this principle was later published [64,65].…”

Neutron shielding assessment of a 16O hadron therapy room by means of Monte Carlo simulations with the PHITS code

“…Around such facilities, various kinds of secondary particles and radiations are produced during the treatment when the accelerated particles interact with the materials composing the accelerator, the beam transport lines and the patient itself, where the treatment beam is eventually stopped [6]. To protect clinical and technical staff, as well as the public, from such ionising and undesirable secondary radiation, each facility must be equipped with adequate shielding to reduce doses to a level as low as reasonably achievable.…”

Entwicklung eines Profilmonitors auf Szintillationsfaser-Basis für Ionenstrahlen niedriger Intensität am Heidelberger Ionenstrahl-Therapiezentrum

“…haben eine geringere Ladung, aber noch einen sehr hohen Impuls. Dadurch bewegen sie sich weiter in umliegendes Gewebe hinter dem Zielvolumen und deponieren dort unerwünscht Dosis, welche als Tail-Dosis bezeichnet wird [42]. Die Fragmente können aber auch komplett aus dem Patienten austreten.…”