XRay Functions

Control panel

Allows operator to set exposure time, mA, and kVp.

On/off switch

Supplies electrical power to the X-ray unit.

Exposure button

Activates X-ray production when pressed.

Milliamperage (mA)

Controls the quantity (number) of X-rays produced.

Kilovoltage peak (kVp)

Controls the penetrating power and energy of X-rays.

Exposure time

Determines how long X-rays are produced.

Step-up transformer

Increases voltage from incoming current to high kVp needed to produce X-rays.

Step-down transformer

Decreases voltage to heat the filament in the cathode.

Autotransformer

Adjusts voltage before it enters the high-voltage circuit; controls kVp selection.

Filament circuit

Provides low voltage current to heat the tungsten filament.

High-voltage circuit

Provides high voltage to accelerate electrons from cathode to anode.

Tubehead

Metal housing that contains X-ray tube and insulating oil.

X-ray tube

Glass vacuum tube where X-rays are produced.

Cathode

Negative electrode; contains tungsten filament and focusing cup; source of electrons.

Tungsten filament

Heated to release electrons via thermionic emission.

Focusing cup

Directs electrons toward the anode target.

Anode

Positive electrode; attracts electrons and converts their energy into X-rays.

Tungsten target

Area of anode struck by electrons to produce X-rays.

Copper stem

Dissipates heat away from tungsten target.

Insulating oil

Prevents overheating and absorbs excess heat.

Lead-lined tubehead

Prevents radiation from escaping in unwanted directions.

Aluminum filter

Removes low-energy (long wavelength) X-rays from the beam.

Collimator

Restricts size and shape of X-ray beam to reduce patient exposure.

Position indicating device (PID)

Directs and shapes the X-ray beam toward the receptor.

Lead apron

Protects patient from scatter radiation.

Thyroid collar

Protects thyroid gland from scatter radiation.