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Other Publications (32)
- Progress in Neurological Surgery
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- Physics in Medicine and Biology
- Physics in Medicine and Biology
- International Journal of Radiation Oncology, Biology, Physics
- International Journal of Radiation Oncology, Biology, Physics
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- International Journal of Radiation Oncology, Biology, Physics
- Current Opinion in Neurology
- International Journal of Radiation Oncology, Biology, Physics
- International Journal of Radiation Oncology, Biology, Physics
- Radiation Oncology (London, England)
- Physics in Medicine and Biology
- Frontiers in Oncology
- Radiation Oncology (London, England)
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- International Journal of Radiation Oncology, Biology, Physics
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- Journal of Applied Clinical Medical Physics / American College of Medical Physics
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- Radiotherapy and Oncology : Journal of the European Society for Therapeutic Radiology and Oncology
- Acta Neurochirurgica
- Acta Neurochirurgica
- Technology in Cancer Research & Treatment
- International Journal of Radiation Oncology, Biology, Physics
Articles by Thierry Gevaert in JoVE
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Dynamic Lung Tumor Tracking voor stereotactische Ablatieve Body Radiation Therapy
Charles A. Kunos1, Jeffrey M. Fabien1, John P. Shanahan1, Christine Collen2, Thierry Gevaert2, Kenneth Poels2, Robbe Van den Begin2, Benedikt Engels2, Mark De Ridder2
1Department of Radiation Oncology, Summa Cancer Institute, 2Department of Radiation Oncology, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel
Other articles by Thierry Gevaert on PubMed
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The Effect of Tomotherapy Imaging Beam Output Instabilities on Dose Calculation
Physics in Medicine and Biology.
Jun, 2010 |
Pubmed ID: 20442461 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.
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Computer-aided Analysis of Star Shot Films for High-accuracy Radiation Therapy Treatment Units
Physics in Medicine and Biology.
May, 2012 |
Pubmed ID: 22538289 As mechanical stability of radiation therapy treatment devices has gone beyond sub-millimeter levels, there is a rising demand for simple yet highly accurate measurement techniques to support the routine quality control of these devices. A combination of using high-resolution radiosensitive film and computer-aided analysis could provide an answer. One generally known technique is the acquisition of star shot films to determine the mechanical stability of rotations of gantries and the therapeutic beam. With computer-aided analysis, mechanical performance can be quantified as a radiation isocenter radius size. In this work, computer-aided analysis of star shot film is further refined by applying an analytical solution for the smallest intersecting circle problem, in contrast to the gradient optimization approaches used until today. An algorithm is presented and subjected to a performance test using two different types of radiosensitive film, the Kodak EDR2 radiographic film and the ISP EBT2 radiochromic film. Artificial star shots with a priori known radiation isocenter size are used to determine the systematic errors introduced by the digitization of the film and the computer analysis. The estimated uncertainty on the isocenter size measurement with the presented technique was 0.04 mm (2σ) and 0.06 mm (2σ) for radiographic and radiochromic films, respectively. As an application of the technique, a study was conducted to compare the mechanical stability of O-ring gantry systems with C-arm-based gantries. In total ten systems of five different institutions were included in this study and star shots were acquired for gantry, collimator, ring, couch rotations and gantry wobble. It was not possible to draw general conclusions about differences in mechanical performance between O-ring and C-arm gantry systems, mainly due to differences in the beam-MLC alignment procedure accuracy. Nevertheless, the best performing O-ring system in this study, a BrainLab/MHI Vero system, and the best performing C-arm system, a Varian Truebeam system, showed comparable mechanical performance: gantry isocenter radius of 0.12 and 0.09 mm, respectively, ring/couch rotation of below 0.10 mm for both systems and a wobble of 0.06 and 0.18 mm, respectively. The methodology described in this work can be used to monitor mechanical performance constancy of high-accuracy treatment devices, with means available in a clinical radiation therapy environment.
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Feasibility of Using the Vero SBRT System for Intracranial SRS
Journal of Applied Clinical Medical Physics / American College of Medical Physics.
2014 |
Pubmed ID: 24423838 The Vero SBRT system was benchmarked in a planning study against the Novalis SRS system for quality of delivered dose distributions to intracranial lesions and assessing the Vero system's capacity for SRS. A total of 27 patients with one brain lesion treated on the Novalis system, with 3 mm leaf width MLC and C-arm gantry, were replanned for Vero, with a 5 mm leaf width MLC mounted on an O-ring gantry allowing rotations around both the horizontal and vertical axis. The Novalis dynamic conformal arc (DCA) planning included vertex arcs, using 90° couch rotation. These vertex arcs cannot be reproduced with Vero due to the mechanical limitations of the O-ring gantry. Alternative class solutions were investigated for the Vero. Additionally, to distinguish between the effect of MLC leaf width and different beam arrangements on dose distributions, the Vero class solutions were also applied for Novalis. In addition, the added value of noncoplanar IMRT was investigated in this study. Quality of the achieved dose distributions was expressed in the conformity index (CI) and gradient index (GI), and compared using a paired Student's t-test with statistical significance for p-values ≤ 0.05. For lesions larger than 5 cm3, no statistical significant difference in conformity was observed between Vero and Novalis, but for smaller lesions, the dose distributions showed a significantly better conformity for the Novalis (ΔCI = 13.74%, p = 0.0002) mainly due to the smaller MLC leaf width. Using IMRT on Vero reduces this conformity difference to nonsignificant levels. The cutoff for achieving a GI around 3, characterizing a sharp dose falloff outside the target volume was 4 cm3 for Novalis and 7 cm3 for Vero using DCA technique. Using noncoplanar IMRT, this threshold was reduced to 3 cm3 for the Vero system. The smaller MLC and the presence of the vertex fields allow the Novalis system to better conform the dose around the lesion and to obtain steeper dose falloff outside the lesion. Comparable dosimetric characteristics can be achieved with Vero for lesions larger than 3 cm3 and using IMRT.
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