34 research outputs found

    Treatment of Head and Neck Cancers Using Radiotherapy

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    Radiotherapy is one of the major treatments for head and neck cancers. This chapter discusses the importance of radiotherapy in treating the common types of head and neck cancers, which can be used as a primary treatment or as a postoperative adjuvant treatment to increase the survival of head and neck cancer patients. Because head and neck cancers are likely to be closely surrounded by radiation-sensitive vital organs, the dosimetric superiority of intensity-modulated radiotherapy (IMRT) to achieve highly conformal dose to the planning target volume (PTV) and avoidance of organs at risk (OARs) helps maintain the cornerstone role of radiotherapy in treating the disease. The rationale of IMRT and the treatment planning technique are introduced. Treatment planning of radiotherapy is one of the key procedures in IMRT. The inverse planning process involves many decision-making steps, including PTV and OAR delineation, beam arrangement settings, objective function setting, etc. These important steps are all illustrated in the chapter, with a specific discussion of planning challenges relevant to head and neck cancers. Finally, the promises for further development of IMRT in terms of OARs dose sparing and PTV dose escalation are briefly discussed and reviewed

    The Nano-X Linear Accelerator: A Compact and Economical Cancer Radiotherapy System Incorporating Patient Rotation.

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    Rapid technological improvements in radiotherapy delivery results in improved outcomes to patients, yet current commercial systems with these technologies on board are costly. The aim of this study was to develop a state-of-the-art cancer radiotherapy system that is economical and space efficient fitting with current world demands. The Nano-X system is a compact design that is light weight combining a patient rotation system with a vertical 6 MV fixed beam. In this paper, we present the Nano-X system design configuration, an estimate of the system dimensions and its potential impact on shielding cost reductions. We provide an assessment of implementing such a radiotherapy system clinically, its advantages and disadvantages compared to a compact conventional gantry rotating linac. The Nano-X system has several differentiating features from current radiotherapy systems, it is [1] compact and therefore can fit into small vaults, [2] light weight, and [3] engineering efficient, i.e., it rotates a relatively light component and the main treatment delivery components are not under rotation (e.g., DMLCs). All these features can have an impact on reducing the costs of the system. In terms of shielding requirements, leakage radiation was found to be the dominant contributor to the Nano-X vault and as such no primary shielding was necessary. For a low leakage design, the Nano-X vault footprint and concrete volume required is 17 m2 and 35 m3 respectively, compared to 54 m2 and 102 m3 for a conventional compact linac vault, resulting in decreased costs in shielding. Key issues to be investigated in future work are the possible patient comfort concerns associated with the patient rotation system, as well as the magnitude of deformation and subsequent adaptation requirements

    ESTRO-EANO guideline on target delineation and radiotherapy details for glioblastoma

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    BACKGROUND AND PURPOSE Target delineation in glioblastoma is still a matter of extensive research and debate. This guideline aims to update the existing joint European consensus on delineation of the clinical target volume (CTV) in adult glioblastoma patients. MATERIAL AND METHODS The ESTRO Guidelines Committee identified 14 European experts in close interaction with the ESTRO clinical committee and EANO who discussed and analysed the body of evidence concerning contemporary glioblastoma target delineation, then took part in a two-step modified Delphi process to address open questions. RESULTS Several key issues were identified and are discussed including i) pre-treatment steps and immobilisation, ii) target delineation and the use of standard and novel imaging techniques, and iii) technical aspects of treatment including planning techniques and fractionation. Based on the EORTC recommendation focusing on the resection cavity and residual enhancing regions on T1-sequences with the addition of a reduced 15 mm margin, special situations are presented with corresponding potential adaptations depending on the specific clinical situation. CONCLUSIONS The EORTC consensus recommends a single clinical target volume definition based on postoperative contrast-enhanced T1 abnormalities, using isotropic margins without the need to cone down. A PTV margin based on the individual mask system and IGRT procedures available is advised; this should usually be no greater than 3 mm when using IGRT

    Impact of MLC properties and IMRT technique in meningioma and head-and-neck treatments

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    Purpose: The impact of multileaf collimator (MLC) design and IMRT technique on plan quality and delivery improvements for head-and-neck and meningioma patients is compared in a planning study. Material and methods: Ten previously treated patients (5 head-and-neck, 5 meningioma) were re-planned for step-and-shoot IMRT (ssIMRT),sliding window IMRT (dMLC) and VMAT using the MLCi2 without (-) and with (+) interdigitation and the Agility-MLC attached to an Elekta 6MV linac. This results in nine plans per patient. Consistent patient individual optimization parameters are used. Plans are generated using the research tool Hyperion V2.4 (equivalent to Elekta Monaco 3.2) with hard constraints for critical structures and objectives for target structures. For VMAT plans, the improved segment shape optimization is used. Critical structures are evaluated based on QUANTEC criteria. PTV coverage is compared by EUD, D-mean, homogeneity and conformity. Additionally, MU/plan, treatment times and number of segments are evaluated. Results: As constrained optimization is used, all plans fulfill the hard constraints. Doses to critical structures do not differ more than 1Gy between the nine generated plans for each patient. Only larynx, parotids and eyes differ up to 1.5Gy (D-mean or D-max) or 7 % (volume-constraint) due to (1) increased scatter,(2) not avoiding structures when using the full range of gantry rotation and (3) improved leaf sequencing with advanced segment shape optimization for VMAT plans. EUD, Dmean, homogeneity and conformity are improved using the Agility-MLC. However, PTV coverage is more affected by technique. MU increase with the use of dMLC and VMAT, while the MU are reduced by using the Agility-MLC. Fastest treatments are always achieved using Agility-MLC, especially in combination with VMAT. Conclusion: Fastest treatments with the best PTV coverage are found for VMAT plans with Agility-MLC, achieving the same sparing of healthy tissue compared to the other combinations of ssIMRT, dMLC and VMAT with either MLCi2(-/+) or Agility

    Feasibility of magnetic resonance imaging-based radiation therapy for brain tumour treatment

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    Purpose : The increasing use of MRI alongside CT images has brought about growing interest in trying to determine radiation attenuation information based on MR images only. The primary aim of this thesis is, therefore, to determine what head tissue compartments need to have separate HU values in order to obtain sufficient RT planning accuracy. This can serve as input for an MR-based classification thus enabling pseudo-CT generation in an MR-only RT workflow. Methods: To achieve this target, flattened (stratified) CT images (fCT) were generated and compared to the original CT images. Mean (ME) and mean absolute (MAE) errors were used for the fCT quality assessment, as was dose comparisons. 70 CT-based RT plans were generated and the dose distributions compared to those obtained when using the different fCT versions in place of the original CT images. The dose agreement was assessed using DVH and 1%/1mm gamma analysis. Results: The lowest MAE of 59.63 HU was calculated for an fCT8 version. DVH analysis showed low differences in the range between 3% (water-filled fCT) and 0.05% depending on the tissue stratification of the fCT version. 1%/1mm gamma analysis correctly identified plans where insufficiently fine-grained tissue classification was the main reason for dose discrepancy. The best RT planning accuracy was obtained for the fCT5 with segmented air cavities, fat, water-rich tissue, spongy, and compact bone, and for the fCT8 where also the brain tissue was stratified. Conclusions: The small differences in dose accuracy between CT and fCT images shows the feasibility of using MR-only RT planning for the brain. Nonetheless, other aspects of the MR-only workflow, such as patient positioning, as well as the impact of e.g. the surgical incisions in the skull should be subject to further research

    Automated Treatment Planning and Non-coplanar Beam Angles in Radiotherapy

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    Automation of the treatment plan generation in radiotherapy showed to play a key role in patient care. It can highly improve plan quality, reduce planner influence, increase standardization and easily generate a high numb