title: Co-60 tomotherapy: a treatment planning investigation.
abstract: OBJECTIVE
  The authors investigate the plan quality and treatment times that may be achieved with Co-60 tomotherapy delivery for clinical IMRT cases.
  
  
  METHODS
  A research version of PINNACLE treatment planning system software (V9.1) enabled the authors to specify custom source profiles for modeling of cylindrical Co-60 sources. The calculated profiles were validated against measurements for simulated MLC leaf openings. The reduction in dose due to a partially obscured source was analyzed. The thread effect was investigated for a source of typical linac spot dimensions and 2.0 and 2.8 cm diameter cylindrical Co-60 sources. Co-60 tomotherapy plans for three clinical treatment sites--prostate, brain, and head-and-neck--were generated for the Co-60 sources and compared to linac-based segmental IMRT plans in terms of the DVHs produced. Treatment times were also determined.
  
  
  RESULTS
  The custom source profile utility allowed the authors to obtain good agreement between calculated and measured profiles for simulated MLC leaf openings with the commercial Co-60 source. It was found that the thread effect is significantly reduced for Co-60 sources and is not a clinical concern even for the large slice width (4.8 cm) and pitch value (0.5) studied. Co-60 tomotherapy plans for three clinical treatment sites compared favorably to the original segmental IMRT plans in terms of the DVHs produced. Treatment times, comparable to the actual segmental IMRT treatment times, may be achieved for a high activity Co-60 source and dual-slice delivery may reduce these times further.
  
  
  CONCLUSIONS
  It may be possible to achieve clinically viable treatment times with Co-60 tomo-therapy delivery without unacceptable loss of plan quality in terms of the DVHs produced.
authors: Department of Medical Physics, Saskatoon Cancer Centre, Saskatoon, Saskatchewan S7N 4H4, Canada. pat.cadman@saskcancer.ca
authors: Patrick
authors: P
authors: Cadman
authors: Karl
authors: K
authors: Bzdusek
mesh_terms: D003037:Cobalt Radioisotopes / Q000627:therapeutic use; D006801:Humans; D011878:Radiotherapy / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D003037:Cobalt Radioisotopes