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Collen C.,Oncology Center University Hospital Brussels Brussel | Engels B.,Oncology Center University Hospital Brussels Brussel | Duchateau M.,Oncology Center University Hospital Brussels Brussel | Tournel K.,Oncology Center University Hospital Brussels Brussel | And 4 more authors.
International Journal of Radiation Oncology Biology Physics | Year: 2010

Purpose: To assess the internal organ motion of the cervix and uterus by megavoltage computed tomography (MVCT) during intensity-modulated radiotherapy (IMRT). Methods and Materials: Ten patients with Stage IIB-IVA cervical cancer underwent daily MVCT imaging. Internal organ motion was evaluated on 150 pretreatment MVCT images by measuring shifts in their boundaries between the MVCT and kilovoltage (kV) planning CT scan in the anterior, posterior, left and right lateral, and superior and inferior direction. Additional intrafractional patient movement was evaluated on 50 posttreatment MVCT images. Results: Measured cervical motion (mean ± SD) was 0.4 ± 10.1 mm in the anterior, -3.0 ± 6.9 mm in the posterior direction, -3.5 ± 4.9 mm in the left and 0.2 ± 4.5 mm in the right lateral direction, 2.2 ± 8.0 mm in the superior and 0.5 ± 5.0 mm in the inferior direction. Compared to the cervix, larger uterine motion was observed. Patient movement during treatment was limited to 1.1 ± 1.3 mm, -0.3 ± 1.6 mm, and 0.2 ± 2.3 mm in anteroposterior, laterolateral and superoinferior direction respectively. Conclusions: MVCT imaging can be used to study patient setup accuracy and cervical and uterine motion during IMRT. This data may be used to refine treatment margins. Copyright © 2010 Elsevier Inc. Source

Duchateau M.,Oncology Center University Hospital Brussels Brussel | Tournel K.,Oncology Center University Hospital Brussels Brussel | Verellen D.,Oncology Center University Hospital Brussels Brussel | Van De Vondel I.,Oncology Center University Hospital Brussels Brussel | And 6 more authors.
Physics in Medicine and Biology | Year: 2010

A radiotherapy treatment plan is based on an anatomical 'snapshot' of the patient acquired during the preparation stage using a kVCT (kilovolt computed tomography) scanner. Anatomical changes will occur during the treatment course, in some cases requiring a new treatment plan to deliver the prescribed dose. With the introduction of 3D volumetric on-board imaging devices, it became feasible to use the produced images for dose recalculation. However, the use of these on-board imaging devices in clinical routine for the calculation of dose depends on the stability of the images. In this study the validation of tomotherapy MVCT (megavolt computed tomography) produced images, for the purpose of dose recalculation by the Planned Adaptive software, has been performed. To investigate the validity of MVCT images for dose calculation, a treatment plan was created based on kVCT-acquired images of a solid water phantom. During a period of 4 months, MVCT images of the phantom have been acquired and were used by the planned adaptive software to recalculate the initial kVCT-based dose on the MVCT images. The influence of the adapted IVDTs (image value-to-density tables) has been investigated as well as the effect of image acquisition with or without preceding airscan. Output fluctuations and/or instabilities of the imaging beam result in MV images of different quality yielding different results when used for dose calculation. It was shown that the output of the imaging beam is not stable, leading to differences of nearly 3% between the original kV-based dose and the recalculated MV-based dose, for solid water only. MVCT images can be used for dose calculation purposes bearing in mind that the output beam is liable to fluctuations. The acquisition of an IVDT together with the MVCT image set, that is going to be used for dose calculation, is highly recommended. © 2010 Institute of Physics and Engineering in Medicine. Source

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