Treatment Planning

Radiation therapy presents an effective and non-invasive option for cancer treatment. However, the use of ionizing radiation can also be harmful and the effects and side effects of irradiation need to be balanced. We develop algorithms and systems to identify the optimal trade-off among the various objectives, e.g., dose in the target, dose in critical structures, or treatment time.

Primarily we study methods from mathematical and heuristic optimization to solve large scale multi-objective planning problems. For example, our inhouse treatment planning software allows for flexible implementation and evaluation of novel algorithms and has been adapted to robotic radiosurgey and HDR brachytherapy.

Selected publications

T. Yu, F.-A. Siebert, A. Schlaefer (2018). A stochastic optimization approach accounting for uncertainty in HDR brachytherapy needle Placement. International Journal of Computer Assisted Radiology and Surgery CARS 2018. 13 (Suppl 1), 34-35.

S. Gerlach, I. Kuhlemann, F. Ernst, C. Fürweger, A. Schlaefer (2017). Impact of robotic ultrasound image guidance on plan quality in SBRT of the prostate. The British Journal of Radiology. 90 (1078), 20160926.

A. Schlaefer, T. Viulet, A. Muacevic, C. Fürweger (2013). Multicriteria optimization of the spatial dose distribution. Med Phys. 40 (12), 121720.

A. Schlaefer, A. Schweikard, (2008). Stepwise multi-criteria optimization for robotic radiosurgery. Med Phys. 35 (5), 2094-2103.

A. Schlaefer, J. Fisseler, S. Dieterich, H. Shiomi, K. Cleary, A. Schweikard (2005). Feasibility of four-dimensional conformal planning for robotic radiosurgery. Med Phys. 32 (12), 3786-3792.

 

 

3D Inverse Planning

Particularly, we are interested in multi-criteria treatment planning for robotic radiosurgery. Here, the kinematic flexibility of a robotic device like the CyberKnife (Accuray Inc.) is used to generate highly conformal dose distributions. With our inhouse developed and workflow based treatment planning system, we have a flexible setup to study different planning approaches. We have previously studied the effect of the spatial beam arrangement on the achievable dose distribution, and how to efficiently search for a suitable set of treatment beams. 

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Interactive Multi-Criteria Optimization

Identifying the optimal trade-off can be hard for a limited number of objectives on the dose in the target and surrounding structures. However, it becomes even more complicated when local dose gradients are involved. Here, the issue is not only to obtain objective values, but also to convey the many potential trade-offs to the user. We are working on novel approaches to place objectives interactively and we study constraints in a 3D visualization of the planning problem.

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Planning for Motion Compensated Treatments

When active motion compensation is employed, the treatment beams follow the motion of the target region. One of the important issues is the remaining relative motion with respect to all tissue not exhibiting the same motion pattern as the target. This issue can be addressed in a 4D planning problem. Another issue is to detect the motion itself. For example, including a robot for obtaining abdominal ultrasound during a fraction will limit the beam delivery, i.e., the beams may not collide or pass through the robot or ultrasound probe. We  study the effect of the imaging devices on the treatment plan quality and develop methods to integrate ultrasound and beam delivery.

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Contact

Opens internal link in new windowAlexander Schlaefer (schlaefer(at)tuhh.de)

References

  • S. Gerlach, I. Kuhlemann, P. Jauer, R. Bruder, F. Ernst, C. Fürweger, A. Schlaefer (2016). Feasibility of robotic ultrasound guided SBRT of the prostate. CARS 2016 Proceedings, supplement of the International Journal of CARS accepted. [BibTex]

  • T. Viulet, O. Blanck, A. Schlaefer (2014). SU-E-T-258:Parallel Optimization of Beam Configurations for CyberKnife Treatments. Medical Physics. 41 (283), [doi] [BibTex]

  • T. Viulet, O. Blanck, A. Schlaefer (2014). SU-E-T-42:Analysis of Spatial Trade-Offs for a Spinal SRS Case. Medical Physics. 41 (231), [doi] [BibTex]

  • A. Schlaefer, T. Viulet, A. Muacevic, C. Fürweger (2013). Multicriteria optimization of the spatial dose distribution. Med Phys. 40 (12), 121720. [doi] [BibTex]

  • A. Schlaefer, S. Dieterich (2011). Feasibility of case-based beam generation for robotic radiosurgery. Artif Intell Med. 52 (2), 67-75. [doi] [BibTex]

  • T. Viulet, N. Rzezovski, A. Schlaefer (2011). Towards interactive planning for radiotherapy by three-dimensional iso-dose manipulation. [BibTex]

  • T. Viulet, N. Rzezovski, A. Schlaefer (2011). Three-Dimensional Isodose Surface Manipulation for Multi-Criteria Inverse Planning in Radiosurgery. [doi] [BibTex]

  • A. Schlaefer, T. Wolschon (2010). Optimizing the Trade-Off Between Number of Beam Starting Points and Plan Quality in Robotic Radiosurgery. [BibTex]