Tomotherapeutic megavoltage CT calibration

A calibration of the University of Wisconsin Tomotherapy Benchtop megavoltage CT (MVCT) system was investigated. It was found that IMVCT values correlate extremely well with electron density and that unlike kilovoltage CT, this correlation is well maintained for higher atomic number materials, and is more robust for different patient sizes and locations. Thus, small improvements in dosimetric calculations should be possible by deriving input images from MVCT as opposed to kVCT, as well as calibrating in terms of electron density, as opposed to physical density.