An investigation of beam parameters for Co-60 tomotherapy.
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.
Cadman
Pat
P
Department of Medical Physics, Saskatoon Cancer Centre, Saskatoon, Saskatchewan S7N 4H4, Canada. pat.cadman@scf.sk.ca
D000465:Algorithms; D001921:Brain / Q000473:pathology*; D003037:Cobalt Radioisotopes / Q000627:therapeutic use*; D003201:Computers; D004867:Equipment Design; D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D006801:Humans; D016011:Normal Distribution; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000295:instrumentation / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012984:Software
D003037:Cobalt Radioisotopes