X-ray tubes have external and internal parts. External parts include the tube support, glass or metal envelope, and protective housing. Tube supports allow positioning of the heavy x-ray tube and come in ceiling, floor-to-ceiling, and C-arm configurations. The internal glass or metal envelope maintains a vacuum and supports the cathode and anode assemblies. The cathode consists of a tungsten filament and focusing cup that guides electrons. The anode is made of heat-dissipating materials like tungsten and receives electrons, producing x-rays and heat.

1. PARTS OF X-RAY TUBE

2. X-Ray tube comprises of the
following two parts:
 External parts
 Internal parts

3. Externalparts
 Tube support
 Glass/metal envelop
 Protective housing

4. TUBE SUPPORT:
 X-ray tube and housing assembly are quite
heavy ,and therefore require a support
mechanism so that the radiologic
technologist can position it.
 There are three methods of x-ray tube
support:
(a)Ceiling support system.
(b)Floor to ceiling support system.
(c)C-arm support system.

5. (a)Ceiling support system:
The ceiling support system
is probably the most
frequently used. It consist
of 2 perpendicular sets of
ceiling-mounted rails . This
allow for both longitudinal
and transverse travel of
the x-ray tube.

6. (b)Floor to ceiling
support system:
The Floor to ceiling support system has
a single column with rollers at each
end, one attached to a ceiling mounted
rail and the other attached to a floor
mounted rail. The tube slides up and
down the column as the column
rotates. A variation of this type of
support system has the column
positioned on a single floor support
system using one or two floor mounted
rails.

7. c)C-arm support system:
Interventional radiology suites
often are equipped with C-arm
support systems, so called
because the system is shaped
like a letter “C”. These system
are ceiling mounted and provide
for very flexible x-ray tube
positioning. The image receptor
is attached to the other end of
the C-arm from the x-ray tube.
Variations called L-arm or U-arm
support are also common.

8. Envelope (Glass or metal) :
 The glass enclosure is made of Pyrex glass.
 The envelope maintains a vacuum inside the
tube to allow more efficient x-ray production and
longer tube life. Usually all current high-capacity
x-ray tube use metal enclosures.
 The primary functions of the envelope is to
provide support and electrical insulation for the
anode and cathode assemblies.

9. Protective housing

10. Internal parts:
 Cathode
 Anode

11. Cathode:
 Cathode is the negative side of the X-ray tube
and consists of the following two parts:
1-Filament
2-Focusing cup

12. 1- Filament :
 Filament is a coil of wire usually 2 mm in
diameter and 1 or 2 cm long.
 The filaments are made of tungsten.
 Filaments must be able to: –
 Boil off electrons (thermionic emission)

13. 2- Focusing cup:
 The filament is embedded in a metal cup
called the focusing cup.
 The purpose of the focusing cup is to guide
the electron stream to the target area on the
anode. Because of the tremendous amount of
heat that is generated at the cathode, the
structure is made of tungsten which has
excellent thermal properties.

14. The anode is the positive side of the x-ray tube,
electricity is conducted and radiates heat and
contains the target. The anode must be a good
thermal dissipator . Because when the projectile
electrons from the cathode interact with the
anode, more than 99% of their kinetic energy is
converted into heat. This heat must be
dissipated quickly. Most common material used
is tungsten but Copper, molybdenum, and
graphite are also common anode materials.
Anode: