Spatiotemporal Fractionation Schemes for Irradiating Large Cerebral Arteriovenous Malformations

Unkelbach, Jan; Bussière, Marc R.; Chapman, Paul H.; Loeffler, Jay S.; Shih, Helen A.

doi:10.1016/j.ijrobp.2016.02.001

Cited by 18 publications

(27 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this case, arc therapy plans can be created in such a way that each fraction delivers high single-fraction doses to complementary parts of the target volume while creating a similar dose bath in the surrounding normal tissue. This was demonstrated for fractionated radiosurgery treatments of large arteriovenous malformations (Unkelbach et al 2016). The optimization of spatiotemporally fractionated treatments is far more challenging than conventional IMRT/IMPT optimization.…”

Section: Spatiotemporal Fractionation Schemesmentioning

confidence: 86%

Optimization of spatiotemporally fractionated radiotherapy treatments with bounds on the achievable benefit

Gaddy¹,

Yıldız²,

Unkelbach³

et al. 2018

Phys. Med. Biol.

Self Cite

View full text Add to dashboard Cite

Abstract. Spatiotemporal fractionation schemes, that is, treatments delivering different dose distributions in different fractions, can potentially lower treatment side effects without compromising tumor control. This can be achieved by hypofractionating parts of the tumor while delivering approximately uniformly fractionated doses to the surrounding tissue. Plan optimization for such treatments is based on biologically effective dose (BED); however, this leads to computationally challenging nonconvex optimization problems. Optimization methods that are in current use yield only locally optimal solutions, and it has hitherto been unclear whether these plans are close to the global optimum. We present an optimization framework to compute rigorous bounds on the maximum achievable normal tissue BED reduction for spatiotemporal plans.The approach is demonstrated on liver tumors, where the primary goal is to reduce mean liver BED without compromising any other treatment objective. The BED-based treatment plan optimization problems are formulated as quadratically constrained quadratic programming (QCQP) problems.First, a conventional, uniformly fractionated reference plan is computed using convex optimization. Then, a second, nonconvex, QCQP model is solved to local optimality to compute a spatiotemporally fractionated plan that minimizes mean liver BED, subject to the constraints that the plan is no worse than the reference plan with respect to all other planning goals. Finally, we derive a convex relaxation of the second model in the form arXiv:1712.03046v1 [physics.med-ph] 8 Dec 2017Spatiotemporal fractionation with bounds on the achievable benefit 2 of a semidefinite programming (SDP) problem, which provides a rigorous lower bound on the lowest achievable mean liver BED.The method is presented on 5 cases with distinct geometries. The computed spatiotemporal plans achieve 12-35 percent mean liver BED reduction over the optimal uniformly fractionated plans. This reduction corresponds to 79-97 percent of the gap between the mean liver BED of the uniform reference plans and our lower bounds on the lowest achievable mean liver BED. The results indicate that spatiotemporal treatments can achieve substantial reductions in normal tissue dose and BED, and that local optimization techniques provide high-quality plans that are close to realizing the maximum potential normal tissue dose reduction.

show abstract

Section: Spatiotemporal Fractionation Schemesmentioning

confidence: 86%

Optimization of spatiotemporally fractionated radiotherapy treatments with bounds on the achievable benefit

Gaddy¹,

Yıldız²,

Unkelbach³

et al. 2018

Phys. Med. Biol.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Spatiotemporal fractionation schemes have recently arisen as a promising treatment technique for photon radiotherapy for healthy tissue sparing. 1,2 Unlike conventional fractionation, spatiotemporally fractionated treatments alter the dose distribution in each fraction in an attempt to optimally exploit the fractionation effect and approximate an ideal treatment that would simultaneously hypofractionate the tumor while delivering a conventionally fractionated dose to healthy tissues. Spatiotemporal fractionation schemes achieve this by delivering high single-fraction doses to different parts of the tumor in each fraction while avoiding a similar localized hypofractionation in the healthy tissue.…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, the benefit for photon therapy has been demonstrated in stereotactic body radiotherapy of liver tumors in cases where the uninvolved liver is the main dose-limiting organ 5 and in radiosurgery for large cerebral arteriovenous malformations. 2 The rationale, however, is somewhat different than for proton treatments. In this case, using a sufficiently large number of beams (or arc therapy delivery), treatment plans can be created in such a way that the fractions deliver high single-fraction doses to complementary parts of the target volume while creating a similar dose bath in the surrounding normal tissue.…”

Section: Introductionmentioning

confidence: 99%

Robust spatiotemporal fractionation schemes in the presence of patient setup uncertainty

Gaddy

Unkelbach²,

Papp

2019

Medical Physics

Self Cite

View full text Add to dashboard Cite

Purpose: Spatiotemporal fractionation schemes for photon radiotherapy have recently arisen as a promising technique for healthy tissue sparing. Because spatiotemporally fractionated treatments have a characteristic pattern of delivering high doses to different parts of the tumor in each fraction, uncertainty in patient positioning is an even more pressing concern than in conventional uniform fractionation. Until now, such concerns in patient setup uncertainty have not been addressed in the context of spatiotemporal fractionation. Methods: A stochastic optimization model is used to incorporate patient setup uncertainty to optimize spatiotemporally fractionated plans using expected penalties for deviations from prescription values. First, a robust uniform reference plan is optimized with a stochastic optimization model. Then, a spatiotemporal plan is optimized with a constrained stochastic optimization model that minimizes a primary clinical objective and constrains the spatiotemporal plan to be at least as good as the uniform reference plan with respect to all other objectives. A discrete probability distribution is defined to characterize the random setup error occurring in each fraction. For the optimization of uniform plans, the expected penalties are computed exactly by exploiting the symmetry of the fractions, and for the spatiotemporal plans, quasi-Monte Carlo sampling is used to approximate the expectation. Results: Using five clinical liver cases, it is demonstrated that spatiotemporally fractionated treatment plans maintain the same robust tumor coverage as a stochastic uniform reference plan and exhibit a reduction in the expected mean BED of the uninvolved liver. This is observed for a spectrum of probability distributions of random setup errors with shifts in the patient position of up to 5 mm from the nominal position. For probability distributions with small variance in the patient position, the spatiotemporal plans exhibit an 8-30% reduction in expected mean BED in the healthy liver tissue for shifts up to 2.5 mm and reductions of 5-25% for shifts up to 5 mm. Conclusions: In the presence of patient setup uncertainty, spatiotemporally fractionated treatment plans exhibit the same robust tumor coverage as their uniformly fractionated counterparts and still retain the benefit in sparing healthy tissues.

show abstract

“…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).…”

Section: Introductionmentioning

confidence: 99%

“…Thereby, some degree of hypofractionation is achieved in the tumor along with near-uniform fractionation in normal tissues. Spatiotemporal fractionation was outlined as an approach to improve fractionated radiosurgery for large cerebral arteriovenous malformations [12]. …”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal fractionation schemes for liver stereotactic body radiotherapy

Unkelbach

Papp

Gaddy

et al. 2017

Radiotherapy and Oncology

Self Cite

View full text Add to dashboard Cite

Background and Purpose Dose prescription in stereotactic body radiotherapy (SBRT) for liver tumors is often limited by the mean liver dose. We explore the concept of spatiotemporal fractionation as an approach to facilitate further dose escalation in liver SBRT. Materials and Methods Spatiotemporal fractionation schemes aim at partial hypofractionation in the tumor along with near-uniform fractionation in normal tissues. This is achieved by delivering distinct dose distributions in different fractions, which are designed such that each fraction delivers a high single fraction dose to complementary parts of the tumor while creating a similar dose bath in the surrounding noninvolved liver. Thereby, higher biologically effective doses (BED) can be delivered to the tumor without increasing the mean BED in the liver. Planning of such treatments is performed by simultaneously optimizing multiple dose distributions based on their cumulative BED. We study this concept for five liver cancer patients with different tumor geometries. Results Spatiotemporal fractionation presents a method of increasing the ratio of prescribed tumor BED to mean BED in the noninvolved liver by approximately 10–20%, compared to conventional SBRT using identical fractions. Conclusions Spatiotemporal fractionation may reduce the risk of liver toxicity or facilitate dose escalation in liver SBRT in circumstances where the mean dose to the non-involved liver is the prescription-limiting factor.

show abstract

Spatiotemporal Fractionation Schemes for Irradiating Large Cerebral Arteriovenous Malformations

Cited by 18 publications

References 14 publications

Optimization of spatiotemporally fractionated radiotherapy treatments with bounds on the achievable benefit

Optimization of spatiotemporally fractionated radiotherapy treatments with bounds on the achievable benefit

Robust spatiotemporal fractionation schemes in the presence of patient setup uncertainty

Spatiotemporal fractionation schemes for liver stereotactic body radiotherapy

Contact Info

Product

Resources

About