Management of Motion and Anatomical Variations in Charged Particle Therapy: Past, Present, and Into the Future

Abstract

The major aim of radiation therapy is to provide curative or palliative treatment to cancerous malignancies while minimizing damage to healthy tissues. Charged particle radiotherapy utilizing carbon ions or protons is uniquely suited for this task due to its ability to achieve highly conformal dose distributions around the tumor volume. For these treatment modalities, uncertainties in the localization of patient anatomy due to inter- and intra-fractional motion present a heightened risk of undesired dose delivery. A diverse range of mitigation strategies have been developed and clinically implemented in various disease sites to monitor and correct for patient motion, but much work remains. This review provides an overview of current clinical practices for inter and intra-fractional motion management in charged particle therapy, including motion control, current imaging and motion tracking modalities, as well as treatment planning and delivery techniques. We also cover progress to date on emerging technologies including particle-based radiography imaging, novel treatment delivery methods such as tumor tracking and FLASH, and artificial intelligence and discuss their potential impact towards improving or increasing the challenge of motion mitigation in charged particle therapy.

National Effort to Re-Establish Heavy Ion Cancer Therapy in the United States

“…Toshiba Corporation developed a more compact and lighter weight commercially available gantry using super conducting magnet technology which was installed and is in clinical use at QST Hospital ( 61 ). Moreover, techniques to mitigate the motion of the tumor and surrounding normal organs (such as breath hold, rescanning, and respiratory gated ion beam deliveries) have also been developed and implemented to treat moving targets with scanning beams ( 62 ). These technological advancements have been adopted by commercial vendors (three Japanese and one European) to transform a system that had previously existed as an experimental system in physics research labs into commercial clinical solutions, which are currently in clinical operation at the 14 international centers listed above.…”

The LET trilemma: Conflicts between robust target coverage, uniform dose, and dose‐averaged LET in carbon therapy

“…Robust optimization has been studied extensively for intensity-modulated proton therapy (IMPT), 11 and has later been adapted and made clinically available for optimization of RBE-weighted dose for carbon ions. 12 Recent publications on RBE-weighted robust optimization for carbon therapy include the studies by Wolf et al 13 and Meschini et al 14 on 4D optimization to handle respiratory motion.…”

“…Therefore, robust optimization taking range uncertainty into account may be utilized to obtain treatment plans that are insensitive to range variations. Robust optimization has been studied extensively for intensity‐modulated proton therapy (IMPT), 11 and has later been adapted and made clinically available for optimization of RBE‐weighted dose for carbon ions 12 . Recent publications on RBE‐weighted robust optimization for carbon therapy include the studies by Wolf et al 13 .…”

Characteristics of breathing‐adapted gating using surface guidance for use in particle therapy: A phantom‐based end‐to‐end test from CT simulation to dose delivery

“…7,[10][11][12][13] These challenges become more essential in implementing tumor treatment approaches that use high doses with extremely steep dose gradients. [14][15][16][17] Compared to photons, ion beams exhibit this latter advantage by delivering a higher conformal dose distribution to a deeply located target with a less integral dose to OARs. 14,[18][19][20] Nowadays, various treatment approaches are employed in clinical practice to address intra-fractional tumor motion during both treatment planning and dose delivery.…”

“…These variations may cause image artifacts, distort the assessment of the tumor trajectory and lead to an undesired dose distribution to the target volume and OARs (such as motion interplay effect) 7,10–13 . These challenges become more essential in implementing tumor treatment approaches that use high doses with extremely steep dose gradients 14–17 . Compared to photons, ion beams exhibit this latter advantage by delivering a higher conformal dose distribution to a deeply located target with a less integral dose to OARs 14,18–20 …”