All the advancements in X-ray tubes till date are done to increase the Tube heat storage capacity thus increasing the lifetime of x -ray tubes. This slide explains about these recent advancements in x-ray tubes.
2. History
X-ray tubes evolved from experimental Crookes tubes with which X-rays were first
discovered on 1895, by the German physicist Wilhelm Conrad Röntgen.
Also callled Cold cathode type X-ray tubes.
Electrons formed by ionization of Gas inside the tube.
Platinum Anode Used.
3. Coolidge Tube
Introduced in 1913
Hot Cathode X-ray tube
Works on principle of thermionic Emission.
Stationary Anode X-ray Tube
Based on model of coolidge tube
Tube was modified ie; More Cylinderical with
Modified cooling techniques.
4. Modern X-ray Tube
Introduced in 1929
Modified Coolidge tube
Contains Rotor and Stator Coils with ball bearing system.
Rotation 3000 RPM
5. Advancement in Rotating Anode X-ray Tube
Dual Focus X-ray tube
Two filaments Used
Most of diagnostic tubes have two focal spots; Large and small
Large is used when large body parts are imagined - high heat
Small is used when better spatial resolution is desired – better detail
Small Focal track is superimposed over large focal track
6. Advancement in Rotating Anode X-ray Tube
New Anode material used Tungsten (90%) – Rhenium (10%) Alloy on
Molybednum backed on Graphite for good Heat Storage and dissipation.
Lubrication material used in bearings of Rotor-stator coil- Silver powder which
allows high rotation
Increased speed of Rotation 9000 – 10,000 RPM allows use of high mA and
shorter exposure time.
Reduced Anode angle ie; 6°
7. Straton Tube
Most advanced technology till date.
Type of Rotating Envelope Tube (RET) introduced by Siemens Medical Solutions
RET-tube implies rotation of the entire tube with respect to the anode axis.
8. Straton Tube
Characteristic features
Electron beam is shaped and controlled by magnetic field.
Cooling surface of anode in direct contact with cooling fluid.
A rotating envelope
9. Straton Tube
It consist of four systems
I. Tube Envelope system
II. Electron Emission system
III. Magnetic deflection system
IV. Cooling system
10. Straton Tube
Tube Envelope system
Material used – Non Magnetic stainless steel
Directly attached to anode disc
Annular/Circular Window (Thickness – 0.2 mm)
Maximum rotation speed – 9600 RPM
11. Straton Tube
Anode Assembly
Target Track made up of-
90% Tungsten and 10% Rhenium
Anode Disc is made up of-
Tungsten, Zirconium, Molybdenum body (TZM Alloy)
Boilling Point – 4612
Melting Point - 2600
12. Straton Tube
Electron Emission system
Cathode Assembly consist of
I. Focusing Cup
II. Flat Emitter
Shape of emitter is – circular
Material – Tungsten
Thickness - 100µm
Diameter - 5µm
Meander like path – for filament heating
13. Straton Tube
Magnetic Deflection System
There are three coils present-
R – Coil – Deflect the beam Radial direction
onto the focal spot
Q – Coil – Focus beam to determine Size
Phi – Coils – Deflection of flying focal spot
intangential direction
Microcontroller controls individual coil current.
Electronically adjusted focal spot
Best Image quality
14. Straton Tube
Cooling System
Unlike other rotating anode x-ray tube which dissipates heat by radiation,
Straton tubes dissipates heat by convection process.
Anode Disc comes in direct contact with cooling Oil.
Oil rotation is turbine flow
Flow of oil - during exposure is 25 ltr/Min
- during pump running 8 ltr/Min
Oil used – Mineral Oil
When apower of 100 KW is applied , the temprature of focal spot reaches
2500°C and temprature on focal track reaches 2000°C. But the back of anode
has temprature of 200°C.
This difference in temprature is due to direct cooling.
15. Advantages
Better Heat Dissipation
Various size multiple focal spot
Longer tube life
Can be used in high KV and high mA technique for prolonged Duration. Ie;
High mAs