Practical Aspects of Implementation of Helical Tomotherapy for Intensity-modulated and Image-guided Radiotherapy

ArticleinClinical Oncology 22(4):294-312 · March 2010with16 Reads
DOI: 10.1016/j.clon.2010.02.003 · Source: PubMed
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.
    • "There are no published recommendations for extending this service to TomoTherapy. As a result UK users of TomoTherapy have been achieving traceability to NPL of chamber calibrations using alanine, as described in the appendix of Burnet et al (2010). The aim of this addendum is to enable users of the NPL absorbed dose service to apply the IPSM 1990 CoP to TomoTherapy. "
    [Show abstract] [Hide abstract] ABSTRACT: The current UK code of practice for high-energy photon therapy dosimetry (Lillicrap et al 1990 Phys. Med. Biol. 35 1355-60) gives instructions for measuring absorbed dose to water under reference conditions for megavoltage photons. The reference conditions and the index used to specify beam quality require that a machine be able to set a 10 cm × 10 cm field at the point of measurement. TomoTherapy machines have a maximum collimator setting of 5 cm × 40 cm at a source to axis distance of 85 cm, making it impossible for users of these machines to follow the code. This addendum addresses the specification of reference irradiation geometries, the choice of ionization chambers and the determination of dosimetry corrections, the derivation of absorbed dose to water calibration factors and choice of appropriate chamber correction factors, for carrying out reference dosimetry measurements on TomoTherapy machines. The preferred secondary standard chamber remains the NE2611 chamber, which with its associated secondary standard electrometer, is calibrated at the NPL through the standard calibration service for MV photon beams produced on linear accelerators with conventional flattening filters. Procedures are given for the derivation of a beam quality index specific to the TomoTherapy beam that can be used in the determination of a calibration coefficient for the secondary standard chamber from its calibration certificate provided by the NPL. The recommended method of transfer from secondary standard to field instrument is in a static beam, at a depth of 5 cm, by sequential substitution or by simultaneous side by side irradiation in either a water phantom or a water-equivalent solid phantom. Guidance is given on the use of a field instrument in reference fields.
    Full-text · Article · Feb 2014
    • "Rekomendacja zmodyfikowanego modelu BTE. Bauman G, 2007 [31] (London, Kanada) 60 1,5 roku Tomoterapia Analiza opisowa Burnet NG, 2010 [32] (Cambridge, Anglia) 114 1 rok Tomoterapia Analiza opisowa Sterzing F, 2008 [33] (Heidelberg, Niemcy) 150 2 lata Tomoterapia Analiza opisowa Bijdekerke P, 2008 [34] (Bruksela, Belgia) 99 1 rok Tomoterapia Propozycja modelu OTT i analiza danych własnych w oparciu o zaproponowany model Piotrowski T, 2013 [4] "
    [Show abstract] [Hide abstract] 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.
    Full-text · Article · Nov 2013
    • "The patients were imaged each day before treatment and the MV-CT scan compared to the planning kV-CT treatment planning scan. Soft-tissue prostate match was performed with 4 degrees of freedom (x, y, z and roll) to give relevant couch moves, using the methods described by Burnet et al. [13]. Once couch and roll adjustments were made the patient underwent the planned treatment fraction. "
    [Show abstract] [Hide abstract] 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.
    Full-text · Article · Oct 2013
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