Upload
utkarsh-ghagare
View
216
Download
0
Embed Size (px)
Citation preview
8/12/2019 Presentation on X-Rays Machine
1/17
8/12/2019 Presentation on X-Rays Machine
2/17
Group Members
Omkar Mhapsekar
Sagar Newase
Sairaj Teli
8/12/2019 Presentation on X-Rays Machine
3/17
A bit of History
Will iam Roentgen dis co vered X-rays in 1895 . Roentg en w as award ed th e Nob el Prize in 1901.
X-ray have the following properties :-1. Travel in straight lines2. Are exponentially absorbed in matter with the
exponent proportional to the mass of the
absorbing material3. Darken photographic plates4. Make shadows of absorbing material on
photosensitive paper
8/12/2019 Presentation on X-Rays Machine
4/17
X-rays are electromagneticradiation of exactly the same
nature as light but of very muchshorter wavelength.
8/12/2019 Presentation on X-Rays Machine
5/17
X-ray are produced when acceleratedelectrons collide with the target. The loss of energy of electrons due to impactis manifested as x-rays. X-ray radiation produced in an x-ray tube.
Most of kinetic energy of electrons of theelectrons striking the target is converted intoheat , less than 1% being transformed into x-rays.
8/12/2019 Presentation on X-Rays Machine
6/17
Production of x-ray includes Glass enclosure , Cathodeand Anode
It is necessary to seal the twoelectrode of the x-ray tube invacuum.
The shape and size of these x-raytubes are specifically designed toprevent electric discharge betweenthe electrodes.
The connecting wires must besealed into the glass wall of the x-
ray tube .
During operation of x-ray tubeboth the glass and the connectingwires are heated to hightemperatures.
GLA SS ENCLOSURE :
Because of the difference in theircoefficients of expansion mostmetals expand more than glasswhen heated.
This difference in expansion wouldcause the glass metal seal to breakand would destroy the vacuum inthe tube if special precautions werenot taken.
Because of this problem, specialallows having approximately thesame coefficients of linearexpansion as pyrex lass aregenerally used in x-ray tubes.
8/12/2019 Presentation on X-Rays Machine
7/17
LINE FOCUS PRINCIPLE
NEED:-I. 99% energy is converted into heatII. Less than1% is converted into x-rayIII. Large focal spotIV. Small focal area
LINE FOCUS PRINCIPLE(1981):-I. Size and shape of focal spotII. Size and shape of electron stream
8/12/2019 Presentation on X-Rays Machine
8/17
LINE FOCUS PRINCIPLE
Target face is placed at angle about 5-20degree to cathode.
Actual focal spot size is increased.
8/12/2019 Presentation on X-Rays Machine
9/17
LINE FOCUS PRINCIPLEThe EffectiveFocal Spot is thebeam projectedonto the patient.
As the anode angledecreases, theeffective focal spotdecreases.
Diagnostic tubetarget angles rangefrom 5 to 15.
8/12/2019 Presentation on X-Rays Machine
10/17
ADVANTAGES
The advantage of Line focus is itprovides the sharpness of the small focalspot with the heat capacity of the largelarge focal spot.
Smaller target angles will producesmaller effective focal spots and sharperimages.
8/12/2019 Presentation on X-Rays Machine
11/17
LIMITATIONS Area covered by thebeam reduces withtarget angle
To cover a 17 theangle must be 12
To cover 36 the anglemust be 14
Anode heel effect .
8/12/2019 Presentation on X-Rays Machine
12/17
CATHODE AND ANODE
8/12/2019 Presentation on X-Rays Machine
13/17
Cathode
Cathode is a source of
electrons which consist offilament and focusing cup.
It supply both voltage andamperage.
It is made up of Tungstenwire of about 2mm indiameter.
Definition:-The negatively charged electrode by which electrons enter
an electrical device.
8/12/2019 Presentation on X-Rays Machine
14/17
As current flows through this finetungsten wire it becomes heated andcauses thermionic emission.
The electron cloud surrounding thefilament produced by the thermionicemission is called Edison Effect.
Space charge effect is also observedwhich has to limit the emission of moreelectrons from the filament.
Cont..
8/12/2019 Presentation on X-Rays Machine
15/17
AnodeDefinition:-
The positively charged electrode by which the electronsleave an electrical device.
8/12/2019 Presentation on X-Rays Machine
16/17
Anode consist of small plate of tungsten which is 2mm or 3mmthick.
Tungsten is used because it has high atomic number, melting
point.If Cu anode is used it acts to increase the total thermal capacity
of the anode and also increases rate of cooling.
The rotating anode principle is used to produce X-ray tubesCapable of withstanding the heat generated by large exposure.
The anode of rotating anode too consist of large disc of tungstenwhich rotates at 3600 rpm.
Cont..
8/12/2019 Presentation on X-Rays Machine
17/17