Adaptation of telecobalt unit for stereotactic irradiation

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Isocentric telecobalt units are traditionally used for conventional radiotherapy.
• Advanced techniques like stereotactic radiotherapy require precise beam delivery and dose conformity.

Purpose of the Study:

• To assess the feasibility of adapting an isocentric telecobalt unit (Th780 C) for stereotactic radiotherapy.
• To compare the dosimetric characteristics of Cobalt-60 (60Co) beams with 6 MV linear accelerator (linac) beams for stereotactic treatment planning.

Main Methods:

• Development of specialized collimator inserts, collimator mount, and couch mount for the telecobalt unit.
• Characterization of narrow 60Co beams.
• Comparative treatment planning using a 3D system for 6 MV and 60Co beams.
• Analysis of beam penumbra, dose-volume histograms (DVH), and equivalent fall-off distance (EFOD).

Main Results:

• The beam penumbra of 60Co beams was larger than that of 6 MV beams.
• Dose-volume histograms for target and non-target tissues were comparable between 60Co and 6 MV plans.
• Equivalent fall-off distances were found to be insignificant, indicating similar dose fall-off characteristics.

Conclusions:

• The dose fall-off of 60Co stereotactic plans is comparable to 6 MV stereotactic plans.
• Cobalt-60, with a 5-mm margin, presents a cost-effective alternative to linac-based stereotactic radiotherapy.