gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

Prototype of real-time tumor-tracking system without implanted fiducial marker for proton therapy

Meeting Abstract

  • T. Terunuma - University of Tsukuba, Tskuba, Ibaraki, Japan
  • T. Sakae - University of Tsukuba, Tskuba, Ibaraki, Japan
  • M. Ishida - University of Tsukuba, Tskuba, Ibaraki, Japan
  • M. Sato - University of Tsukuba, Tskuba, Ibaraki, Japan
  • K. Yasuoka - University of Tsukuba, Tskuba, Ibaraki, Japan
  • H. Kumada - University of Tsukuba, Tskuba, Ibaraki, Japan
  • T. Okumura - University of Tsukuba, Tskuba, Ibaraki, Japan
  • K. Tsuboi - University of Tsukuba, Tskuba, Ibaraki, Japan
  • H. Sakurai - University of Tsukuba, Tskuba, Ibaraki, Japan

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog200

DOI: 10.3205/09ptcog200, URN: urn:nbn:de:0183-09ptcog2004

Veröffentlicht: 24. September 2009

© 2009 Terunuma et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Purpose: We developed a real-time tumor-tracking system without implanted fiducial marker. The purpose of this study is to verify technical accuracy of the system.

Methods and materials: The developed tumor-tracking system utilizes a fluoroscopic x-ray image and patient’s respiratory waveform. The latter was measured by using a laser displacement sensor as movement of patient’s abdomen surface. Tumor position was calculated by a pattern-matching algorithm which based on the normalized cross-correlation between a tumor template image and the fluoroscopic image. The template image need not be geometrical shape as implanted fiducial marker and can be selected as an arbitrary region of DRR or fluoroscopic image. The system can output a beam-extraction trigger when following conditions are satisfied 1) the displacement of tumor position is within ±2.0 mm, and 2) the respiration phase is exhale.

Results: The process time for pattern matching was depends on the size of template image. The maximum process time was 5 msec and it was less than the time interval of the fluoroscopic image acquisition (33 msec). Thus, a real time processing was achieved. Moreover, for a typical template image size (32*32 pixel; 16*16 mm), 4 image-tracking was possible within the time interval. Accuracy of tumor-tracking depended on both of the image contrast and image size. Successful tracking in all respiration phase was performed in case that the template image had high-contrast, such as a diaphragm, relatively dense tumor in lung and a contrast medium in liver after Transcatheter Arterial Embolization (TAE). In case of low-contrast image, under the limit of around exhale-phase, the tumor-tracking was smooth and then probability of false positive was very low. For example, within exhale-phase corresponding to under 30% level of respiratory waveform, the tracking error was less than 0.4 mm (1s) in H-F direction.

Conclusion: Combination internal/external information is effective to carry out the real-time tumor-tracking without implanted fiducial maker.