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Co‐60 tomotherapy: A treatment planning investigation

2011; Wiley; Volume: 38; Issue: 2 Linguagem: Inglês

10.1118/1.3533668

2473-4209

Patrick Cadman, K Bzdusek,

Radiation Therapy and Dosimetry

The authors investigate the plan quality and treatment times that may be achieved with Co-60 tomotherapy delivery for clinical IMRT cases.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.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.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.