Journal Article

Adequate target volume in total-body irradiation by intensity-modulated radiation therapy using helical tomotherapy: a simulation study

Ryosuke Takenaka, Akihiro Haga, Hideomi Yamashita and Keiichi Nakagawa

in Journal of Radiation Research

Volume 58, issue 2, pages 210-216
Published in print March 2017 | ISSN: 0449-3060
Published online December 2016 | e-ISSN: 1349-9157 | DOI: http://dx.doi.org/10.1093/jrr/rrw115
Adequate target volume in total-body irradiation by intensity-modulated radiation therapy using helical tomotherapy: a simulation study

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  • Clinical Genetics
  • Molecular Biology and Genetics
  • Epidemiology
  • Radiology
  • Nuclear Chemistry, Photochemistry, and Radiation

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Abstract

Recently, intensity-modulated radiation therapy (IMRT) has been used for total-body irradiation (TBI). Since the planning target volume (PTV) for TBI includes the surrounding air, a dose prescription to the PTV provides high fluence to the body surface. Thus with just a small set-up error, the body might be exposed to a high-fluence beam. This study aims to assess which target volume should be prescribed the dose, such as a clinical target volume (CTV) with a margin, or a CTV that excludes the surface area of the skin. Three treatment plans were created for each patient: the 5-mm clipped plan (Plan A), the 0-mm margin plan (Plan B) and the 5-mm margin plan (Plan C). The CTV was the whole body. PTVs were the CTV with the exception of 5 mm from the skin surface in Plan A, equal to the CTV in Plan B, and the CTV with a 5 mm margin in Plan C. The prescribed dose was 12 Gy in six fractions. To assess the influence of the set-up error, dose distributions were simulated on computed tomography (CT) images shifted 2 pixels (= 4.296 mm), 5 pixels (= 10.74 mm) and 10 pixels (= 21.48 mm) in the lateral direction from the original CT. With a set-up error of 10.74 mm, V110% was 8.8%, 11.1% and 23.3% in Plans A, B and C, respectively. The prescription to the PTV containing the surrounding air can be paradoxically vulnerable to a high-dose as a consequence of a small set-up error.

Keywords: total-body irradiation; intensity-modulated radiation therapy; helical tomotherapy; set-up error; PTV margin

Journal Article.  3063 words.  Illustrated.

Subjects: Clinical Genetics ; Molecular Biology and Genetics ; Epidemiology ; Radiology ; Nuclear Chemistry, Photochemistry, and Radiation

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