Translational and rotational localization errors in cone-beam CT based image-guided lung stereotactic radiotherapy

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Abstract

PURPOSE: Accurate localization is crucial in delivering safe and effective stereotactic body radiation therapy (SBRT). The aim of this study was to analyse the accuracy of image-guidance using the cone-beam computed tomography (CBCT) of the VERO system in 57 patients treated for lung SBRT and to calculate the treatment margins.

MATERIALS AND METHODS: The internal target volume (ITV) was obtained by contouring the tumor on maximum and mean intensity projection CT images reconstructed from a respiration correlated 4D-CT. Translational and rotational tumor localization errors were identified by comparing the manual registration of the ITV to the motion-blurred tumor on the CBCT and they were corrected by means of the robotic couch and the ring rotation. A verification CBCT was acquired after correction in order to evaluate residual errors.

RESULTS: The mean 3D vector at initial set-up was 6.6±2.3mm, which was significantly reduced to 1.6±0.8mm after 6D automatic correction. 94% of the rotational errors were within 3°. The PTV margins used to compensate for residual tumor localization errors were 3.1, 3.5 and 3.3mm in the LR, SI and AP directions, respectively.

CONCLUSIONS: On-line image guidance with the ITV-CBCT matching technique and automatic 6D correction of the VERO system allowed a very accurate tumor localization in lung SBRT.

Original languageEnglish
Pages (from-to)859-65
Number of pages7
JournalPhysica Medica
Volume32
Issue number7
DOIs
Publication statusPublished - Jul 2016

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  • Journal Article

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