High-Accuracy Head Tracking for Cranial Radiation Therapy

Project Description

Thermoplastic mask

Compensating for patient motion constitutes a challenging as well as important problem for high precision cranial radiotherapy. Common approaches rely on patient immobilization using stereotactic frames, masks or bite bars, or employ X-ray based monitoring and motion compensation such as the 6D skull tracking used by the CyberKnife®. These techniques entail several drawbacks: First, the mask systems are rather inconvenient and also not tolerated by all patients. They further provide no motion monitoring during the treatment - the patient is assumed to be fixed. This is indeed only true up to errors in millimeter range. Second, X-ray based imaging exposes the subject to an unnecessary amount of additional radiation. This exposure also limits the head-tracking speed to about 1 Hz.

Therefore, marker-less optical head-tracking provides a promising alternative, where a laser constantly scans the patient's forehead. This approach requires only light patient fixation  and  provides a basis for fast real-time monitoring. While promising results have already been achieved using commercial systems such as the Microsoft Kinect®, the accuracy still lags behind the desirable standard of sub-millimeter accuracy. One major drawback of marker-less tracking is given by the lack of point-to-point correspondences. Finding these, for objects which are not strictly rigid, is challenging and prone to registration errors. Point cloud matching algorithms are used which rely, if at all, on a few spatial landmarks. The surface geometry very often introduces further ambiguities which lead to a convergence into local error minima and hence poor robustness.

Figure (1) Laser scanning optics, (2) Laser scan of the forehead, (3) MRI segmented tissue ground truth.

  • MRI segmented tissue ground truth

By combining expertise from the fields of computer science, electronics, applied mathematics, machine learning and biomedical optics our research group works on laser triangulation, dedicated electronic and optical hardware, as well as enhanced tracking approaches. Specifically the feasibility of optically detecting subcutaneous as well as cutaneous structures is evaluated. The structures serve as supportive landmarks and can be used to localize rigid cranial bone. To uncover these landmarks the developed system extracts optical  backscatter features. These are obtained from near-infrared (NIR) laser scans of the forehead. Finally, machine learning algorithms such as Gaussian Processes or Support Vector regression are used to obtain the tissue thickness. In cooperation with Varian Medical, Inc., the world-leading manufacturer for LINACs, we develop a novel prototype for high-accuracy head-tracking  in radiotherapy.

 

 

Figure (1) Triangulated 3D surface point cloud, (2) feature-labeled point cloud, (3) reconstructed tissue-labeled point cloud.

  • Triangulated 3D surface point cloud
  • Feature-labeled point cloud
  • Reconstructed tissue-labeled point cloud

Publications

Responsible

Floris Ernst
Bldg 64 / Room 95 +49 451 31015208


Jirapong Manit
Bldg 64 / Room 88 +49 451 31015216


2017

Jirapong Manit, Achim Schweikard and Floris Ernst, Deep Convolutional Neural Network Approach for Forehead Tissue Thickness Estimation from NIR Laser Backscattering Images, in: Proceedings of the 51st DGBMT Annual Conference, Dresden, Germany, pages submitted, 2017
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Jirapong Manit, Christina Bremer, Achim Schweikard and Floris Ernst, Patient identification using a near-infrared laser scanner, in: Medical Imaging 2017: Image-Guided Procedures, Robotic Interventions, and Modeling, SPIE, Orlando, FL, pages 101352L, SPIE, 2017
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2016

Tobias Wissel, Patrick Stüber, Benjamin Wagner, Ralf Bruder, Christian Erdmann, Christin-Sophie Deutz, Benjamin Sack, Jirapong Manit, Achim Schweikard and Floris Ernst, Enhanced Optical Head Tracking for Cranial Radiotherapy: Supporting Surface Registration by Cutaneous Structures (2016), in: International Journal of Radiation Oncology, Biology, Physics, 95:2(810-817)
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2015

Jirapong Manit, Tobias Wissel, Patrick Stüber, Achim Schweikard and Floris Ernst, A Study of Gaussian Noise Effects on Skin Thickness Measurement, in: Proceedings of the 49th DGBMT Annual Conference, Lübeck, Germany, pages S190, 2015
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Patrick Stüber, Benjamin Wagner, Tobias Wissel, Ralf Bruder, Achim Schweikard and Floris Ernst, An Approach to Improve Accuracy of Optical Tracking Systems in Cranial Radiation Therapy (2015), in: Cureus, 7:1(e239)
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Floris Ernst, Achim Schweikard, Patrick Stüber, Ralf Bruder, Benjamin Wagner and Tobias Wissel, Analysis of feature stability for laser-based determination of tissue thickness, in: Advanced Biomedical and Clinical Diagnostic and Surgical Guidance Systems XIII, San Francisco, CA, pages 93130Q, 2015
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S. Lüdtke, Benjamin Wagner, Ralf Bruder, Patrick Stüber, Floris Ernst, Achim Schweikard and Tobias Wissel, Calibration of galvanometric laser scanners using statistical learning methods, in: Bildverarbeitung für die Medizin, Berlin, Heidelberg, New York, pages 467-472, Springer, 2015
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Tobias Wissel, Benjamin Wagner, Patrick Stüber, Achim Schweikard and Floris Ernst, Data-driven Learning for Calibrating Galvanometric Laser Scanners (2015), in: IEEE Sensors Journal, 15:10(5709-5717)
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Tobias Wissel, Patrick Stüber, Benjamin Wagner, Achim Schweikard and Floris Ernst, Efficient Estimation of Tissue Thicknesses using Sparse Approximation for Gaussian Processes, in: 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC '15), EMBS, Milano, Italy, pages 7015-7018, IEEE, 2015
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Tobias Wissel, Patrick Stüber, Benjamin Wagner, Ralf Bruder, Achim Schweikard and Floris Ernst, Enhanced Tissue Thickness Computation by Exploiting Local Neighborhoods, in: Proceedings of the 29th International Congress and Exhibition on Computer Assisted Radiology and Surgery (CARS'15), Barcelona, Spain, 2015
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Tobias Wissel, Patrick Stüber, Benjamin Wagner, Ralf Bruder, Achim Schweikard and Floris Ernst, Enriching 3D optical surface scans with prior knowledge: tissue thickness computation by exploiting local neighborhoods (2015), in: International Journal of Computer Assisted Radiology and Surgery, 11:4(569-579)
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Floris Ernst, Tobias Wissel, Patrick Stüber, Benjamin Wagner, Ralf Bruder and Achim Schweikard, Optical localization of the human skull for cranial radiation therapy, in: Varian Research Partnership Symposium, Varian Medical, 2015
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Benjamin Wagner, Patrick Stüber, Tobias Wissel, Ralf Bruder, Achim Schweikard and Floris Ernst, Ray Interpolation for Generic Triangulation Based on a Galvanometric Laser Scanning System, in: 2015 IEEE International Symposium on Biomedical Imaging, New York, pages 1419-1422, IEEE, 2015
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Tobias Wissel, Patrick Stüber, Benjamin Wagner, Achim Schweikard and Floris Ernst, Tissue Segmentation from Head MRI: A Ground Truth Validation for Feature-Enhanced Tracking, in: Proceedings of the 49th DGBMT Annual Conference, Lübeck, Germany, pages S184, 2015
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Tobias Wissel, Patrick Stüber, Benjamin Wagner, Achim Schweikard and Floris Ernst, Tissue segmentation from head MRI: a ground truth validation for feature-enhanced tracking (2015), in: Current Directions in Biomedical Engineering, 1:1(228-231)
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2014

Patrick Stüber, Tobias Wissel, Benjamin Wagner, Ralf Bruder, Achim Schweikard and Floris Ernst, A comparison of different hardware design approaches for feature-supported optical tracking with respect to angular dependencies, in: 56th Annual Meeting of the AAPM, pages 204, 2014
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Benjamin Wagner, Patrick Stüber, Tobias Wissel, Ralf Bruder, Achim Schweikard and Floris Ernst, Accuracy analysis for triangulation and tracking based on time-multiplexed structured light (2014), in: Medical Physics, 41:8(082701)
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Tobias Wissel, Patrick Stüber, Benjamin Wagner, Ralf Bruder, Achim Schweikard and Floris Ernst, Angle influence and compensation for marker-less head tracking based on laser scanners, in: Proceedings of the 28th International Congress and Exhibition on Computer Assisted Radiology and Surgery (CARS'14), Fukuoka, Japan, pages 62-63, 2014
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Jan Graßhof, Ralf Bruder, Achim Schweikard and Floris Ernst, Kalman Filter based Head Tracking for Cranial Radiation Therapy with low-cost Range-Imaging Cameras, in: Bildverarbeitung für die Medizin 2014, Aachen, Germany, pages 324-329, Springer, 2014
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Floris Ernst, Ralf Bruder, Tobias Wissel, Patrick Stüber, Benjamin Wagner and Achim Schweikard, Measuring cranial soft tissue thickness with MRI or pressure-compensated tracked ultrasound (2014), in: British Journal of Medicine and Medical Research, 4:4(937-948)
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Tobias Wissel, Patrick Stüber, Benjamin Wagner, Robert Dürichen, Ralf Bruder, Achim Schweikard and Floris Ernst, Tissue Thickness Estimation for High Precision Head-Tracking using a Galvanometric Laser Scanner - A Case Study, in: 36th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC '14), EMBS, Chicago, IL, pages 3106-3109, IEEE, 2014
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2013

Benjamin Wagner, Patrick Stüber, Tobias Wissel, Ralf Bruder, Achim Schweikard and Floris Ernst, Accuracy of object tracking based on time-multiplexed structured light, in: 12. Jahrestagung der Deutschen Gesellschaft für Computer- und Roboterassistierte Chirurgie (CURAC), CURAC, Innsbruck, Austria, pages 139-142, 2013
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Patrick Stüber, Tobias Wissel, Benjamin Wagner, Ralf Bruder, Achim Schweikard and Floris Ernst, An improvement for the scanning process in high accuracy head tracking, in: 12. Jahrestagung der Deutschen Gesellschaft für Computer- und Roboterassistierte Chirurgie (CURAC), CURAC, Innsbruck, Austria, pages 179-182, 2013
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Patrick Stüber, Tobias Wissel, Benjamin Wagner, Ralf Bruder, Achim Schweikard and Floris Ernst, Design and evaluation of a highly accurate optical setup for backscatter analysis, in: 44. Jahrestagung der DGMP, DGMP, Cologne, Germany, pages 181-186, 2013
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Tobias Wissel, Ralf Bruder, Achim Schweikard and Floris Ernst, Estimating soft tissue thickness from light-tissue interactions\textemdash a simulation study (2013), in: Biomedical Optics Express, 4:7(1176-1187)
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Michael Hollinde, Für mehr Präzision in der Tumorbestrahlung (2013), in: Lübecker Nachrichten
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Tobias Wissel, Patrick Stüber, Benjamin Wagner, Ralf Bruder, Achim Schweikard and Floris Ernst, Preliminary Study on Optical Feature Detection for Head Tracking in Radiation Therapy, in: 13th IEEE International Conference on BioInformatics and BioEngineering (BIBE), IEEE, Chania, Greece, pages 1-5, 2013
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Floris Ernst, Ralf Bruder, Tobias Wissel, Patrick Stüber, Benjamin Wagner and Achim Schweikard, Real time contact-free and non-invasive tracking of the human skull\textemdash first light and initial validation, in: Applications of Digital Image Processing XXXVI, San Diego, CA, pages 88561G-1 - 88561G-8, 2013
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Jude Dineley, Skin measurements improve motion tracking, medicalphysicsweb.org, 2013
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Tobias Wissel, Ralf Bruder and Achim Schweikard, Skin thickness estimation for high precision optical head tracking during cranial radiation therapy\textemdash a simulation study, in: Proceedings of the 55th Annual Meeting of the {ASTRO}, ASTRO, Atlanta, GA, USA, pages S669, 2013
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Benjamin Wagner, Patrick Stüber, Tobias Wissel, Ralf Bruder, Achim Schweikard and Floris Ernst, Time-multiplexed structured light for head tracking, in: 44. Jahrestagung der DGMP, DGMP, Cologne, Germany, pages 199-202, 2013
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2012

Philipp Grüning, Patrick Stüber, Lars Richter, Oliver Blanck, Ralf Bruder and Achim Schweikard, Estimation of error sources for optical head tracking in cranial radiation therapy, in: 11. Jahrestagung der Deutschen Gesellschaft für Computer- und Roboterassistierte Chirurgie (CURAC), CURAC, 2012
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