Improved delivery efficiency for step and shoot intensity modulated radiotherapy using a fast-tuning magnetron

The delivery efficiency of step and shoot intensity modulated radiotherapy (IMRT) has been improved by the installation of fast-tuning magnetrons into three travelling wave linear accelerators. The IMRT delivery efficiency and the beam start-up performance have been compared before and after install...

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Bibliographic Details
Published in:Physics in medicine & biology 2001-11, Vol.46 (11), p.N253-N261
Main Authors: Budgell, G J, Martens, C, Claus, F
Format: Article
Language:English
Subjects:
Biological and medical sciences
Magnetics
Medical sciences
Miscellaneous
Particle Accelerators
Radiometry
Radiotherapy, Conformal - instrumentation
Radiotherapy, Conformal - methods
Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects)
Reproducibility of Results
Time Factors
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Summary:The delivery efficiency of step and shoot intensity modulated radiotherapy (IMRT) has been improved by the installation of fast-tuning magnetrons into three travelling wave linear accelerators. The IMRT delivery efficiency and the beam start-up performance have been compared before and after installation. Start-up and inter sub-field times were reduced by an average of 3.0 s. A typical start-up time from depression of the start button to beam on is now around 4 s. Delivery efficiency for a variety of clinical and quality control prescriptions was improved by an average of 30.7% (range 7.4-60.9%), depending on a complex combination of the number of sub-fields, distance moved by leaves and dose rate. For the oldest accelerator (7 years old), dosimetric accuracy was significantly improved for low dose sub-fields. The dose output was within 2% for a 1 monitor unit (MU) sub-field and 1% for a 2 MU sub-field. The two newer accelerators displayed similar or better dose characteristics even before fast-tuning magnetron installation. Beam symmetries and flatnesses were acceptable at all energies and dose rates, and showed no obvious degradation in low dose sub-fields. It is recommended that fast-tuning magnetrons are adopted for accelerators of this design performing step and shoot IMRT.
ISSN:0031-9155
1361-6560
DOI:10.1088/0031-9155/46/11/402