Simultaneous optimization of dose distributions and fractionation schemes in particle radiotherapy

Abstract

The paper provides conceptual insight into the interdependence of optimal fractionation schemes and the spatial optimization of dose distributions. It demonstrates the emergence of nonuniform fractionation schemes that arise from the standard BED model when IMPT fields and fractionation scheme are optimized simultaneously. Although the projected benefits are likely to be small, the approach may give rise to an improved therapeutic ratio for tumors treated with stereotactic techniques to high doses per fraction.

Spatiotemporal Fractionation Schemes for Irradiating Large Cerebral Arteriovenous Malformations

“…Thereby, high single fraction doses are delivered to parts of the target volume while simultaneously achieving fractionation in surrounding normal tissues, providing a net improvement of the therapeutic ratio. The use of such nonuniform spatiotemporal fractionation schemes has previously been demonstrated for proton therapy [11,12]. For proton beams, the entrance dose is mostly independent of the proton range, which provides the opportunity to move dose from proximal to distal parts of the target volume without changing the dose in the entrance region.…”

Spatiotemporal fractionation schemes for liver stereotactic body radiotherapy

“…This is in particular the case for liver toxicity endpoints because both fractionation effects and dose-volume effects need to be accounted for in outcome modeling. Generally, it is expected that the benefit of spatiotemporal fractionation over uniform fractionation decreases with lower α / β -ratio for the liver whereas a higher liver α / β -ratio is in favor of spatiotemporal fractionation [14]. However, the dependence of mean liver BED reductions on the α / β -ratio is weak within the range of typically assumed values, which was confirmed by treatment planning experiments.…”

“…Recently, it has been shown that this goal can be achieved to some degree by delivering distinct dose distributions in different fractions. The concept has been named spatiotemporal fractionation [11–14]. …”

“…The concept was initially demonstrated for proton therapy [13, 14] and subsequently for conventional photon beams [11, 12]. The rationale can be understood in the context of rotation therapy delivered with tomotherapy or volumetric-modulated arc therapy (VMAT).…”

Optimization of the fractionated irradiation scheme considering physical doses to tumor and organ at risk based on dose–volume histograms

“…Recently, Mizuta et al have proposed a mathematical method to select a fractionation regimen based on physical dose distribution, 18 and relevant investigations into this have been reported subsequently. [19][20][21][22] Following the paper, 18 the authors also presented a graphical method using a "TO plot" to determine the appropriate fractionation regimen based on the relation between radiation effects on the tumor and an organ at risk (OAR). 23 These studies have shown explicit criteria for selecting better fractionation methods, which are determined by the physical dose distribution and the α/ β value in the linear-quadratic (LQ) model.…”