Nuclear physics in particle therapy: a review

Abstract

Charged particle therapy has been largely driven and influenced by nuclear physics. The increase in energy deposition density along the ion path in the body allows reducing the dose to normal tissues during radiotherapy compared to photons. Clinical results of particle therapy support the physical rationale for this treatment, but the method remains controversial because of the high cost and of the lack of comparative clinical trials proving the benefit compared to x-rays. Research in applied nuclear physics, including nuclear interactions, dosimetry, image guidance, range verification, novel accelerators and beam delivery technologies, can significantly improve the clinical outcome in particle therapy. Measurements of fragmentation cross-sections, including those for the production of positron-emitting fragments, and attenuation curves are needed for tuning Monte Carlo codes, whose use in clinical environments is rapidly increasing thanks to fast calculation methods. Existing cross sections and codes are indeed not very accurate in the energy and target regions of interest for particle therapy. These measurements are especially urgent for new ions to be used in therapy, such as helium. Furthermore, nuclear physics hardware developments are frequently finding applications in ion therapy due to similar requirements concerning sensors and real-time data processing. In this review we will briefly describe the physics bases, and concentrate on the open issues.

Report of a National Cancer Institute special panel: Characterization of the physical parameters of particle beams for biological research

“…Radiochromic film may also have this relationship . While the detector response could be corrected based solely on knowledge of LET in a pure carbon ion beam, substantial fragmentation occurs even before the SOBP . With protons, helium, and boron all contributing dose to variable degrees with depth in a carbon beam, the corresponding relationship between LET and dosimeter response may not be uniquely defined .…”

“…26 While the detector response could be corrected based solely on knowledge of LET in a pure carbon ion beam, substantial fragmentation occurs even before the SOBP. 27 With protons, helium, and boron all contributing dose to variable degrees with depth in a carbon beam, the corresponding relationship between LET and dosimeter response may not be uniquely defined. 28 As a result of these challenges, dosimeters such as film are well suited for relative measurements orthogonal to the beam direction; ion chambers, because of their independence of LET, may be used at any position in the treatment field, including along the beam direction where LET is most variable.…”

Empowering Intensity Modulated Proton Therapy Through Physics and Technology: An Overview

“…The discussion of the I value of tissues is more complicated [3]. Planning systems are commissioned using measurements in water and range uncertainties in tissues are not absolute but derived from measurements in water.…”

“…There is growing interest in and enthusiasm for using proton therapy (PT) in cancer management, as evidenced, in part, by the special issue in 2016 on particle therapy in the International Journal of Radiation Oncology, Biology, Physics [1] and the large number of publications on this topic cited in the book entitled Principles and Practice of Proton Beam Therapy [2] and in other books and articles [3]. According to the Particle Therapy Co-Operative Group (PTCOG), the number of proton therapy centers has increased by 40% within the last three years [4].…”

Monitoring of breathing motion in image-guided PBS proton therapy: comparative analysis of optical and electromagnetic technologies

“…Proton therapy based on pencil beam scanning (PBS) exploits the favourable spatial dose distribution of proton beams for the delivery of highly conformal radiotherapy [1]. However, the physiological deformation of anatomical structures, due to respiratory organ motion, can interplay with the dynamics of dose delivery and, if not taken into account, can detrimentally affect treatment quality for mobile tumours in the thorax and abdomen [2].…”