Lecture 3 ( image production process) Flashcards
Image production process ?
Image acquisition , Image processing , Image archiving , Image display and Image Analysis
Image acquisition ?
Creating x ray beam and creating image
Conventional : Radiographic film , Intensifying screen
Computed radiography : CR cassette , imaging plate
Digital radiography : Detector
Image processing ?
Conventional:- automatic processor
Computed Radiography: Digitizer
Digital radiography:- Digital image processing
Image Archiving and display ?
Conventional:- film , hard copy
Computed Radiography: Monitor, soft image, CD, etc
Digital radiography:- Monitor, soft image
Image analysis :
image quality , pathology
and Radiation protection
what are major components of x ray tubes ?
Cathode , Anode , Glass envelope (metal)
and Tube housing
Cathode ?
X-ray tubes contain a negatively charged , cathode containing the filament that serves as an electron source
The anode and cathode are contained in an evacuated envelope to prevent the electrons from colliding with gas molecules
Anode ( target) ?
The anode is positively charged and includes the target where x-rays are produced
It has two types :
stationary and rotating
Stationary:
is used in dental , some portable machine
Rotating:
used in general purpose to be capable to producing high intensity x-ray beam in short time
Focal spots ?
The focal spot is the apparent source of x-rays in the tube
Focal spot size is a result of the filament shape, focusing cup, and electric field created between the cathode and anode
must be small to produce sharp images, but large enough to tolerate a high heat
Tube housing ?
the envelope is contained in a tube housing that protects and insulates the tube and provides shielding to prevent leakage radiation
The housing contains an oil bath to provide electrical insulation and help cool the tube
x ray production ?
produced when high speed electrons suddenly undergo change in direction
converts the input electric power into output x-ray photons or energy
x ray tube should provide to converts the input into output is ?
Supply of free electrons, Means of electron acceleration and Force to change the direction of the accelerated electron
Production of free electron ?
The Filaments is heated by follow of the electrical current
Due to the heat the electron can break free and leave the filament’s surface to make a cloud or space charge (Thermionic emission)
Acceleration of electron ?
Cathode filament is negative there will be strong repulsion
anode is positive there will be strong attraction
So easily they can move to the anode in high speed
Change the direction ?
Due to the presence of the focusing cup the accelerated electron will be focused and hit the anode in specific area (target)
Which has 2 process ?
Bremsstrahlung and Characteristic
x ray production ?
Accelerated electrons from cathode (filament) to the anode (target) three effect take place:
Heat production , Characteristic x ray
and Bremsstrahlung x ray
