Cristina Garibaldi1, Gaia Piperno2, Annamaria Ferrari2, Alessia Surgo2, Matteo Muto2, Sara Ronchi2, Alessia Bazani3, Floriana Pansini3, Marta Cremonesi4, Barbara Alicja Jereczek-Fossa5, Roberto Orecchia6. 1. Unit of Radiation Research, European Institute of Oncology, Milano, Italy. Electronic address: cristina.garibaldi@ieo.it. 2. Department of Radiation Oncology, European Institute of Oncology, Milano, Italy. 3. Unit of Medical Physics, European Institute of Oncology, Milano, Italy. 4. Unit of Radiation Research, European Institute of Oncology, Milano, Italy. 5. Department of Radiation Oncology, European Institute of Oncology, Milano, Italy; Department of Health Sciences, Università degli Studi di Milano, Milano, Italy. 6. Department of Health Sciences, Università degli Studi di Milano, Milano, Italy; Scientific Director, European Institute of Oncology, Milano, Italy.
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.
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.
Authors: Sarah Barrett; Pierre Thirion; Dean Harper; Andrew J Simpkin; Michelle Leech; Kim Hickey; Laoise Ryan; Laure Marignol Journal: Rep Pract Oncol Radiother Date: 2019-09-04