Particle therapy of moving targets—the strategies for tumour motion monitoring and moving targets irradiation

Abstract

Particle therapy of moving targets is still a great challenge. The motion of organs situated in the thorax and abdomen strongly affects the precision of proton and carbon ion radiotherapy. The motion is responsible for not only the dislocation of the tumour but also the alterations in the internal density along the beam path, which influence the range of particle beams. Furthermore, in case of pencil beam scanning, there is an interference between the target movement and dynamic beam delivery. This review presents the strategies for tumour motion monitoring and moving target irradiation in the context of hadron therapy. Methods enabling the direct determination of tumour position (fluoroscopic imaging of implanted radio-opaque fiducial markers, electromagnetic detection of inserted transponders and ultrasonic tumour localization systems) are presented. Attention is also drawn to the techniques which use external surrogate motion for an indirect estimation of target displacement during irradiation. The role of respiratory-correlated CT [four-dimensional CT (4DCT)] in the determination of motion pattern prior to the particle treatment is also considered. An essential part of the article is the review of the main approaches to moving target irradiation in hadron therapy: gating, rescanning (repainting), gated rescanning and tumour tracking. The advantages, drawbacks and development trends of these methods are discussed. The new accelerators, called "cyclinacs", are presented, because their application to particle therapy will allow making a breakthrough in the 4D spot scanning treatment of moving organs.

Impact of intrafraction prostate motion on clinical target coverage in proton therapy: A simulation study of dosimetric differences in two delivery techniques

“…Many investigators have studied target intrafraction motion and its dosimetric impact on CTV dose coverage in photon and proton radiation therapy . This study focused on the simulation of DS and US proton treatment using real patients’ prostate intrafraction motion traces and relevant clinical treatment plans.…”

Comparison of particle beam therapy and stereotactic body radiotherapy for early stage non-small cell lung cancer: A systematic review and hypothesis-generating meta-analysis

“…Unlike PSPT, which delivers a highly homogeneous dose to a target volume at once, intensity modulated PT (IMPT) through beam scanning is very sensitive to internal tumor motion [123– 125]. This is mainly due to the necessity for precise and accurate dose deposition at specific voxels iso-energy layer by iso-energy layer longitudinally through a tumor target during IMPT.…”

“…Irregularities in respiratory pattern and inconsistencies between the external marker position and the internal target motion remain challenges with gating [128,129]. These issues may be mitigated through the adaptation of amplitude-based gating and internal positional tracking with or without fiducial markers [125,130,131]. Alternative to gating, 4D planning may improve dose conformity and homogeneity, which warrants further clinical exploration [132].…”

Sparse proportional re-scanning with hadron beams

“…(9) is applicable to any irradiation procedures (repeated, layered, volumetric…) and also when tumour tracking is Table 4 Number of spots S k that receive 1 visit, 2 visits, 3 visits… k visits and the total number of visits, V = Σ S k × k, for five different re-scanning strategies. 1 2303 × 1 0 1124 × 1 1604 × 1 1984 × 1 2 0 0 480 × 2 3 0 0 223 × 3 380 × 2 used to follow a moving tumour [24]. Indeed the calculation of the reduction factor does not depend on the movements of the target.…”