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An investigation of beam parameters for Co‐60 tomotherapy
Author(s) -
Cadman Pat
Publication year - 2007
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2776257
Subject(s) - tomotherapy , medical physics , beam (structure) , dosimetry , optics , physics , nuclear medicine , medicine , radiation therapy , radiology
The effect of various physical beam parameters for Co‐60 tomotherapy is examined, including: Cylindrical source size, source‐to‐collimator distance (SCD) and collimator leaf width. In general, beam profile effects are seen with larger Co‐60 sources that are not seen with conventional linacs and multileaf collimators that are used for IMRT, including a broadening of the profile width as the source width increases. A treatment planning study was conducted to evaluate the effect of various beam parameter combinations with planning regions of interest typical of a simultaneous boost head and neck treatment. Combinations of SCD and source FWHM that produce an 80%–20% profile distance less than approximately 0.85 cm at 0.5 cm depth produced a Co‐60 tomotherapy plan with better DVH results than a conventional 7‐field linac plan for a 1 cm leaf width. Further improvement may be achieved by reducing the leaf width. In general it may be concluded that commercially available cylindrical Co‐60 sources of 1.5 – 2.0 cm diameter may be appropriate for tomotherapy if the proper combination of beam parameters is chosen.