Tube rating

Tube ratings are the defined input parameters (kVp, mA, exposure) that can be safely used during its operation without causing damage to the x-ray tube itself and unique to each individual x-ray tube model. An x-ray tube rating is the maximum allowable kilowatts (kW) in 0.1 second .

When the electron beam strikes the target material in the anode only 1% of the kinetic energy of the electrons is converted into x-rays whilst the rest is converted into thermal energy. Increasing the kVp, mA, or exposure time increases the thermal energy produced per examination. Thermal energy is dissipated in the anode and surrounding x-ray tube. If too much heat is created (or not enough is dissipated), excess residual thermal energy will damage the anode and tube.

By creating tube ratings the operator can ensure that the parameters set are appropriate for the examination whilst minimizing the risk of damage to the x-ray tube. Typical x-ray tube ratings are between 5-100kW and are dependent on focal spot size .