MU
Also written as: MU — Monitor Unit
Monitor Unit, the basic unit of measurement for radiation dose delivery calibrated to the output of a linear accelerator.
Full Definition
A Monitor Unit (MU) is the fundamental dosimetric unit used to control radiation dose delivery from linear accelerators and other external beam radiation therapy equipment. One MU is typically calibrated to deliver a specific dose (commonly 1 cGy) under standard reference conditions (usually 10x10 cm field size at 100 cm source-to-surface distance in water). The actual dose delivered varies with field size, depth, and other treatment parameters, requiring calculation factors to determine the correct number of MUs needed for prescribed doses.
Usage
Usage note: Commonly confused with dose units like cGy; MU represents machine output while cGy represents absorbed dose.
In Context
- "The treatment plan specified 180 MU for the anterior field." — Treatment planning document
- "Daily MU calculations were verified by the medical physicist before treatment delivery." — Quality assurance report