Mathematical Modelling of Dose Planning in High Dose-Rate Brachytherapy

Morén, Björn

doi:10.3384/lic.diva-154966

Cited by 2 publications

(7 citation statements)

References 96 publications

(194 reference statements)

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“…Chapter 5 describes the contributions from the papers of this thesis, and topics for future research are suggested in Chapter 6. Chapters 2-6 are partly based on the material in the licentiate thesis [1]. In the second part, five papers are appended, in form of published articles A-C and manuscripts D-E.…”

Section: Outlinementioning

confidence: 99%

“…First, the concept of dose points is introduced, and then we present and discuss several concepts that are used to evaluate dose plans. This section is based on the presentations in the licentiate thesis [1] and Paper D.…”

Section: Clinical Treatment Evaluationmentioning

confidence: 99%

“…In this chapter we introduce three well-studied models for dose planning. These are used or further studied in Papers A, B, C, and E. The model formulations and illustrations are based on the licentiate thesis [1] and the literature review Paper D, which is further discussed in Chapter 5. Table 4.1 introduces the notations in common for the models.…”

Section: Mathematical Models For Dose Planningmentioning

confidence: 99%

“…Tables 4.1 and 4.2 introduce the notation used for the DVM. The following mixed-integer programming (MIP) DVM model is adapted from [53] and [54], and uses the same notation as in [1] and Paper D.…”

Section: Dose-volume Modelsmentioning

confidence: 99%

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Treatment Planning of High Dose-Rate Brachytherapy - Mathematical Modelling and Optimization

Morén

2021

Linköping Studies in Science and Technology. Dissertations

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Cancer is a widespread class of diseases that each year affects millions of people. It is mostly treated with chemotherapy, surgery, radiation therapy, or combinations thereof. High doserate (HDR) brachytherapy (BT) is one modality of radiation therapy, which is used to treat for example prostate cancer and gynecologic cancer. In BT, catheters (i.e., hollow needles) or applicators are used to place a single, small, but highly radioactive source of ionizing radiation close to or within a tumour, at dwell positions. An emerging technique for HDR BT treatment is intensity modulated brachytherapy (IMBT), in which static or dynamic shields are used to further shape the dose distribution, by hindering the radiation in certain directions.The topic of this thesis is the application of mathematical optimization to model and solve the treatment planning problem. The treatment planning includes decisions on catheter placement, that is, how many catheters to use and where to place them, as well as decisions for dwell times. Our focus is on the latter decisions. The primary treatment goals are to give the tumour a sufficiently high radiation dose while limiting the dose to the surrounding healthy organs, to avoid severe side effects. Because these aims are typically in conflict, optimization models of the treatment planning problem are inherently multiobjective. Compared to manual treatment planning, there are several advantages of using mathematical optimization for treatment planning. First, the optimization of treatment plans requires less time, compared to the time-consuming manual planning. Secondly, treatment plan quality can be improved by using optimization models and algorithms. Finally, with the use of sophisticated optimization models and algorithms the requirements of experience and skill level for the planners are lower. The use of optimization for treatment planning of IMBT is especially important because the degrees of freedom are too many for manual planning.The contributions of this thesis include the study of properties of treatment planning models, suggestions for extensions and improvements of proposed models, and the development of new optimization models that take clinically relevant, but uncustomary aspects, into account in the treatment planning. A common theme is the modelling of constraints on dosimetric indices, each of which is a restriction on the portion of a volume that receives at least a specified dose, or on the lowest dose that is received by a portion of a volume. Modelling dosimetric indices explicitly yields mixed-integer programs which are computationally demanding to solve. We have therefore investigated approximations of dosimetric indices, for example using smooth non-linear functions or convex functions. Contributions of this thesis are also a literature review of proposed treatment planning models for HDR BT, including mathematical analyses and comparisons of models, and a study of treatment planning for IMBT, which shows how robust optimization can be used to mitigate the risks fro...

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Section: Outlinementioning

confidence: 99%

Section: Clinical Treatment Evaluationmentioning

confidence: 99%

Section: Mathematical Models For Dose Planningmentioning

confidence: 99%

Section: Dose-volume Modelsmentioning

confidence: 99%

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Treatment Planning of High Dose-Rate Brachytherapy - Mathematical Modelling and Optimization

Morén

2021

Linköping Studies in Science and Technology. Dissertations

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“…In literature, two different approaches for catheter position optimization have been described. 14 The first approach is to optimize the catheter positions independent of the dwell times, [15][16][17] based solely on geometrical properties of target and organs at risk shapes, without clinical evaluation criteria such as dose-volume indices. Such approaches have been shown to perform well when compared to the clinical treatment plans.…”

Section: Introductionmentioning

confidence: 99%

Bi‐objective optimization of catheter positions for high‐dose‐rate prostate brachytherapy

Meer

Bosman

Niatsetski³

et al. 2020

Medical Physics

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Bi-objective simultaneous optimization of catheter positions and dwell times for highdose-rate (HDR) prostate brachytherapy, based directly on dose-volume indices, has shown promising results. However, optimization with the state-of-the-art evolutionary algorithm MO-RV-GOMEA so far required several hours of runtime, and resulting catheter positions were not always clinically feasible. The aim of this study is to extend the optimization model and apply GPU parallelization to achieve clinically acceptable computation times. The resulting optimization procedure is compared with a previously introduced method based solely on geometric criteria, the adapted Centroidal Voronoi Tessellations (CVT) algorithm. Methods: Bi-objective simultaneous optimization was performed with a GPU-parallelized version of MO-RV-GOMEA. This optimization of catheter positions and dwell times was retrospectively applied to the data of 26 patients previously treated with HDR prostate brachytherapy for 8-16 catheters (steps of 2). Optimization of catheter positions using CVT was performed in seconds, after which optimization of only the dwell times using MO-RV-GOMEA was performed in 1 min. Results: Simultaneous optimization of catheter positions and dwell times using MO-RV-GOMEA was performed in 5 min. For 16 down to 8 catheters (steps of 2), MO-RV-GOMEA found plans satisfying the planning-aims for 20, 20, 18, 14, and 11 out of the 26 patients, respectively. CVT achieved this for 19, 17, 13, 9, and 2 patients, respectively. The P-value for the difference between MO-RV-GOMEA and CVT was 0.023 for 16 catheters, 0.005 for 14 catheters, and <0.001 for 12, 10, and 8 catheters. Conclusions: With bi-objective simultaneous optimization on a GPU, high-quality catheter positions can now be obtained within 5 min, which is clinically acceptable, but slower than CVT. For 16 catheters, the difference between MO-RV-GOMEA and CVT is clinically irrelevant. For 14 catheters and less, MO-RV-GOMEA outperforms CVT in finding plans satisfying all planning-aims.

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Mathematical Modelling of Dose Planning in High Dose-Rate Brachytherapy

Abstract: This is a Swedish Licentiate's Thesis Swedish postgraduate education leads to a doctor's degree and/or a licentiate's degree. A doctor's degree comprises 240 ECTS credits (4 years of full-time studies). A licentiate's degree comprises 120 ECTS credits.

Cited by 2 publications

References 96 publications

Treatment Planning of High Dose-Rate Brachytherapy - Mathematical Modelling and Optimization

Treatment Planning of High Dose-Rate Brachytherapy - Mathematical Modelling and Optimization

Bi‐objective optimization of catheter positions for high‐dose‐rate prostate brachytherapy

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