Practical aspects of implementation of helical tomotherapy for intensity-modulated and image-guided radiotherapy.
ABSTRACT Image-guided radiotherapy (IGRT) and intensity-modulated radiotherapy (IMRT) represent two important technical developments that will probably improve patient outcome. Helical tomotherapy, provided by the TomoTherapy HiArt system, provides an elegant integrated solution providing both technologies, although others are available. Here we report our experience of clinical implementation of daily online IGRT and IMRT using helical tomotherapy.
Methods were needed to select patients who would probably benefit. Machine-specific commissioning, a quality assurance programme and patient-specific delivery quality assurance were also needed. The planning target volume dose was prescribed as the median dose, with the added criterion that the 95% isodose should cover 99% of the target volume. Although back-up plans, for delivery on conventional linear accelerators, were initially prepared, this practice was abandoned because they were used very rarely.
In the first 12 months, 114 patients were accepted for treatment, and 3343 fractions delivered. New starts averaged 2.6 per week, with an average of 17.5 fractions treated per day, and the total number capped at 22. This has subsequently been raised to 24. Of the first 100 patients, 96 were treated with radical intent. Five were considered to have been untreatable on our standard equipment. IGRT is radiographer led and all patients were imaged daily, with positional correction made before treatment, using an action level of 1mm. A formal training programme was developed and implemented before installation. The in-room time fell significantly during the year, reflecting increasing experience and a software upgrade. More recently, after a couch upgrade in April 2009, the mean in-room time fell to 18.6 min.
Successful implementation of tomotherapy was the result of careful planning and effective teamwork. Treatment, including daily image guidance, positional correction and intensity-modulated delivery, is fast and efficient, and can be integrated into routine service. This should encourage the adoption of these technologies.
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ABSTRACT: The aim of this study was to review the models that allow the prediction of the length of time of irradiation during radiotherapy and to describe the evolution of the problem of effective time management of medical accelerators following the development of radiation therapy. The analysis was based on the literature data selected using the medical search engine PubMed. Of the 234 publications from the years 1982 to 2013, 16 studies were selected for detailed analysis, which included respectively: 1) the evolution of models used in radiotherapy realised by conventional medical accelerators, 2) the determinants of the failure of these models in radiotherapy realised by unconventional medical accelerators, and 3) proposals for alternative models for these accelerators. The analysis showed that the classical models such as ESTV (equivalent simple treatment visit) or BTE (basic treatment equivalent) effectively describe the performance of conventional linear accelerators used in conventional radiation therapy. Nevertheless, implemen-tation of new procedures such as in vivo dosimetry and image guidance or introducing new technology (multi leaf collimator, dynamic techniques) forces modifications of the developed models. The example of the modified model is the solution developed by the Addenbrooke hospital. The analysed models correctly describe the therapeutic efficiency of conventional linear accelerators. In the case of innovative solutions such as the Cyber Knife, Gamma Knife or Tomotherapy there is a need to develop new models. An example of one of the first models describing the performance of non-conventional linear accelerators is OTT (overall treatment time) developed for the Tomotherapy.Zeszyty Naukowe WCO [Letters in Oncology Science]. 11/2013; 10:65-71.
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ABSTRACT: Intensity-modulated radiotherapy (IMRT) and image-guided radiotherapy offer significant opportunities to improve outcomes for our patients, although they are not yet as widely used as they might be. IMRT allows better target coverage and lower organ at risk doses than conformal therapy. It also allows inhomogeneous dose plans to be developed, where these can provide benefit, either to dose escalate the tumour or reduce dose to adjacent or overlapping organs at risk. Image guidance adds precision and the possibility of careful reduction in planning target volume margins. The technologies can be valuable both for patients with highly malignant tumours, such as glioblastoma, and those with less malignant or benign tumours. In glioblastoma, temozolomide chemotherapy and surgical developments have improved survival, and developments in radiotherapy techniques should also be used to optimise outcome. Target volume delineation, including calculation of the planning target volume margin is critical. Clear definitions of the gross tumour and clinical target volumes are essential, following established guidelines. Normal tissue volume delineation is also essential for IMRT. The planning organ at risk volume has become a valuable tool to manipulate dose away from organs at risk to avoid toxicities. This is distinct from 'optimising volumes' used to drive the computer optimiser during planning. Hard data on central nervous system (CNS) normal tissue tolerance is surprisingly slight, reflecting the clinical imperative to avoid serious complications in neurological tissues. The effect of chemotherapy on radiotherapy tolerance in the CNS remains obscure, and more needs to be done to develop the knowledge base. IMRT provides better conformation of the high dose treatment to the shape of the target, and reduces the dose to normal tissue structures. Image guidance improves the accuracy of dose delivery, which is particularly important where steep dose gradients are present. These technologies should be regarded as the state-of-the-art for our CNS patients.Clinical oncology (Royal College of Radiologists (Great Britain)). 05/2014;
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ABSTRACT: To measure the geometric uncertainty resulting from intra-fraction motion and intra-observer image matching, for patients having image-guided prostate radiotherapy on TomoTherapy. All patients had already been selected for prostate radiotherapy on TomoTherapy, with daily MV-CT imaging. The study involved performing an additional MV-CT image at the end of treatment, on 5 occasions during the course of 37 treatments. 54 patients were recruited to the study. A new formula was derived to calculate the PTV margin for intra-fraction motion. The mean values of the intra-fraction differences were 0.0mm, 0.5mm, 0.5mm and 0.0° for LR, SI, AP and roll, respectively. The corresponding standard deviations were 1.1mm, 0.8mm, 0.8mm and 0.6° for systematic uncertainties (Σ), 1.3mm, 2.0mm, 2.2mm and 0.3° for random uncertainties (σ). This intra-fraction motion requires margins of 2.2mm in LR, 2.1mm in SI and 2.1mm in AP directions. Inclusion of estimates of the effect of rotations and matching errors increases these margins to approximately 4mm in LR and 5mm in SI and AP directions. A new margin recipe has been developed to calculate margins for intra-fraction motion. This recipe is applicable to any measurement technique that is based on the difference between images taken before and after treatment.Radiotherapy and Oncology 10/2013; · 4.52 Impact Factor