X ray production
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X-ray Production. kVp KINETIC ENERGY OF ELECTRONS. CATHODE --------. MADE OF TUNGSTEN + 1%-3% THORIUM. TUNGSTEN. Z # 74 MELTING POINT- 3,410 DEG. CELSIUS. THORIUM. Z # 90. THERMIONIC EMISSION. CATHODE HEATED UP TO AT LEAST 2,200 DEG. CELSIUS. ANODE +++++. TUNGSTEN

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X-ray Production

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X ray production

X-ray Production


X ray production

kVp KINETIC ENERGY OF ELECTRONS


Cathode

CATHODE --------

MADE OF TUNGSTEN+ 1%-3% THORIUM


Tungsten

TUNGSTEN

Z # 74

MELTING POINT- 3,410 DEG. CELSIUS


Thorium

THORIUM

Z # 90


Thermionic emission

THERMIONIC EMISSION

CATHODE HEATED UP TO AT LEAST 2,200 DEG. CELSIUS


Anode

ANODE +++++

TUNGSTEN

TARGET


Tungten as target

TUNGTEN AS TARGET

HIGH Z# - 74------EFFICIENCY OF X-RAY PRODUCTION

HIGH MELTING POINT –3,410 ° C– TARGET HEATED TO 2,000° C


X ray production1

X-RAY PRODUCTION

  • BREMSSTRAHLUNG RADIATION

  • CHARACTERISTIC RADIATION


Bremsstrahlung radiation

BREMSSTRAHLUNG RADIATION

If an incoming free electron gets close to the nucleus of a target atom, the strong electric field of the nucleus will attract the electron, thus changing direction and speed of the electron. The Electron looses energy which will be emitted as an X-ray photon. The energy of this photon will depend on the degree of interaction between nucleus and electron, i.e. the passing distance. Several subsequent interactions between one and the same electron and different nuclei are possible. X-rays originating from this process are called bremsstrahlung. Bemsstrahlung is a German word directly describing the process: "Strahlung" means "radiation", and "Bremse" means "brake


Bremsstrahlung radiation1

Bremsstrahlung Radiation


Brems

BREMS


Different degrees of decceleration

DIFFERENT DEGREES OF DECCELERATION

X-RAYS

HEAT


Brems radiation is

BREMS RADIATION IS:

POLYENERGETIC !

90% OF X-RAYS ARE PRODUCED THROUGH BREMS

INTERACTIONS WHEN 80-100 KVP APPLIED


Brems emission continuous

BREMS EMISSION-CONTINUOUS


Characteristic x rays

Characteristic X-rays

The high energy electron can also cause an electron close to the nucleus in a metal atom to be knocked out from its place. This vacancy is filled by an electron further out from the nucleus. The well defined difference in binding energy, characteristic of the material, is emitted as a monoenergetic photon. When detected this X-ray photon gives rise to a characteristic X-ray line in the energy spectrum.


Characteristic radiation

Characteristic Radiation

KE OF PROJECTILE ELECTRON > BINDING ENERGYORBITAL ELECTRON


Characteristic cascade

CHARACTERISTIC CASCADE


Tungsten 74

TUNGSTEN-74

BINDING ENERGIES

OF DIFFERENT SHELL ELECTRONS

K-70 KEV

L-12 KEV

M-2.8 KEV


Characteristic x rays1

CHARACTERISTIC X-RAYS

L

K

70-12 = 58 keV

70-3 = 67 keV

M

K

M

12-3 = 9 keV

L


Transfer of electrons between outer shells results in

TRANSFER OF ELECTRONS BETWEEN OUTER SHELLS RESULTS IN:

HEAT PRODUCTION !


Each characteristic radiation ex k to l transfer is

EACH CHARACTERISTIC RADIATION ( ex. K TO L TRANSFER) IS:

MONOENERGETIC !

THERE ARE MANY

CHARACTERISTIC RADIATION

PRODUCED IN ONE ATOM

THEREFORE CHARACTERISTIC

RADIATION

IS ALSO POLYENERGETIC !


Characteristic emission less polyenergetic

CHARACTERISTIC EMISSION-LESS POLYENERGETIC!


X rays production an inefficient process

X-RAYS PRODUCTION AN INEFFICIENT PROCESS

80 KVP

99.4% HEAT 0.6% X-RAYS


Efficiency of x ray production

% EFFICIENCY OF X-RAY PRODUCTION

% EFFICIENCY= K * Z * kVp

K = 1 * 10-4


X ray emission

X-RAY EMISSION

  • ISOTROPICAL- IN EVERY DIRECTION


Useful radiation projected toward the patient

USEFUL RADIATION – PROJECTED TOWARD THE PATIENT


Leakage radiation

LEAKAGE RADIATION

HOUSING


Off focus radiation

OFF-FOCUS RADIATION

USEFUL

OFF-FOCUS


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