Basic concepts of CORVUS dose model

Basic concepts of the dose model utilized in the CORVUS treatment planning system are reviewed. Following the Peacock delivery tool (MIMiC) by NOMOS Corporation, CORVUS "delivers" radiation to a patient by means of narrow x-ray beams (pencil beams), which are subject to lateral electronic disequilibrium. Dose data for such beams are difficult to obtain experimentally. Therefore, the CORVUS dose model uses analytically calculated (rather than experimentally measured) narrow-beam dose data. The model is based on the idea that physical parameters necessary to calculate absorbed dose in narrow x-ray beams can be derived from measured broad-beam dose data. Calculation of central-axis and off-axis absorbed dose in narrow beams as well as a method of generating beam profiles are described.