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Recent
Advancements in
Modern X-ray tube

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.

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.

Modern X-ray Tube
 Introduced in 1929
 Modified Coolidge tube
 Contains Rotor and Stator Coils with ball bearing system.
 Rotation 3000 RPM

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

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°

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.

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

Straton Tube
It consist of four systems
I. Tube Envelope system
II. Electron Emission system
III. Magnetic deflection system
IV. Cooling system

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

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

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

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

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.

 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

Thank You
Santosh ojha
santdastan@gmail.com

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Recent advancements in modern x ray tube

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