Comparative analysis of 60Co intensity-modulated radiation therapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Planning

Background:

• Intensity-modulated radiation therapy (IMRT) is a precise radiotherapy technique.
• The use of Cobalt-60 ((60)Co) beams in IMRT is explored as an alternative to linear accelerator (LINAC) generated beams.
• Comparative analysis of different beam energies and delivery techniques is crucial for optimizing treatment plans.

Purpose of the Study:

• To scientifically compare the quality of IMRT treatment plans generated using (60)Co beams versus 6 MV and 18 MV LINAC beams.
• To evaluate the impact of the number of static (60)Co beams and helical tomotherapy geometry on plan quality.
• To assess critical organ sparing and target coverage across different beam configurations and energies.

Main Methods:

• A convex fluence map optimization (FMO) model was employed for plan quality comparison.
• Twenty-five diverse clinical patient cases (head-and-neck, prostate, CNS, breast, lung) were analyzed.
• IMRT plans were generated using 6 MV, 18 MV, and (60)Co dose models with varying numbers of static beams and helical geometry.

Main Results:

• Critical organ sparing improved with more (60)Co beams, with diminishing returns beyond 9 beams for most sites.
• Helical (60)Co tomotherapy achieved comparable plan quality to static plans with 11 beams.
• While 18 MV plans could achieve equivalent target coverage, they required more dose to critical structures compared to 6 MV and (60)Co beams.

Conclusions:

• IMRT with commercially available (60)Co sources and a double-focused MLC shows potential.
• Optimal plan quality and critical organ sparing were best with 6 MV beams, followed closely by (60)Co.
• Beyond 9 beams, improvements in target coverage and organ sparing with (60)Co were marginal, and static plans were comparable to helical tomotherapy.