CT imaging for Cobalt-60 helical tomotherapy

Helical tomotherapy, a new technique under development for Intensity Modulated Radiation Therapy, was first proposed by Mackie et al. in 1993. This treatment modality employs a fan-beam radiation source mounted in a CT-like ring gantry, and rotated about the patient. One of the anticipated benefits of helical tomotherapy is the ability to perform in-situ CT imaging to confirm patient set-up, and to reconstruct the dynamically delivered dose distributions. The feasibility of a tomotherapy device using a Cobalt-60 source has previously been demonstrated. Here an investigation of the imaging capabilities of a Co-60 tomotherapy unit is presented. Preliminary results from simulations and measurements on phantoms containing various test objects indicate that megavoltage CT imaging is possible within the context of a Co-60 tomotherapy device.