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

Intrafractional and interfractional motions of the prostate during Carbon ion therapy: quantification by four-dimensional CT

Meeting Abstract

  • T. Okada - Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
  • H. Tsuji - Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
  • S. Sugahara - Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
  • M. Suzuki - Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
  • M. Kumagai - Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
  • S. Mori - Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
  • S. Minohara - Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
  • T. Kamada - Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan
  • H. Tsujii - Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, 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. Doc09ptcog154

DOI: 10.3205/09ptcog154, URN: urn:nbn:de:0183-09ptcog1542

Veröffentlicht: 24. September 2009

© 2009 Okada 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: Carbon ion radiotherapy (C-ion RT) for the prostate cancer has been performed with hypofractionated regimen at our institute for 14 years. The results so far has been quite satisfactory both in the toxicity and tumor control, and even better results might be expected with more precise and more hypofractionated C-ion RT. It is essential to know how the prostate can move with our immobilization method to realize more precise C-ion RT with smaller PTV margins. In this study, four-dimensional CT (4DCT) was used to measure the intrafractional and interfractional prostate motion to determine the validity of our immobilization method of C-ion RT for the prostate cancer.

Methods and materials: Twenty patients undergoing our treatment between April and August 2008 were enrolled to the study with the written informed consent. The median age was 66.7 years. Of those, 7 high and 11 intermediate risk patients underwent neo-adjuvant androgen deprivation therapy with C-ion RT, and 2 low risk patients received C-ion RT alone. Every patient received C-ion RT in supine position with rigid body cast for the pelvis and under free breathing. The 4DCT images were acquired after the first 5 fractions out of the 16 fractions. All scans were carried out in supine position with the customized body cast as routinely used in actual treatment. To evaluate the influence of respiration on intrafractional motion, scans under both free and gated breathing conditions were performed. The movement of center-of-mass (COM) and edges of prostate were measured. Also interfractional movement of prostate COM was measured from peak exhalation 4DCT images relative to the initial planning CT images.

Results: Under free breathing, the maximum movement of prostate COM was 0.7mm with the mean value of 0.2 mm, and the maximum movement of edges was 1.6 mm with the mean of 0.2 mm. Under gated breathing, the maximum movement of COM was 0.5 mm with the mean of 0.1 mm, and the maximum movement of edges was 1.6 mm with the mean of 0.1 mm. Interfractional displacement of prostate COM was also small enough to perform C-ion RT with the current PTV margins.

Conclusions: The intrafractional and interfractional prostate motions were both sufficiently small to perform the current C-ion RT with our immobilization method. Further, particularly small intrafractional motion will enable us to apply dynamic irradiation using scanning beam with this immobilization method under free breathing only by verification of initial position of the prostate.