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Irene Gold PART 2 Supplemental: XRAY – Qs & As
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Irene Gold PART 2 Supplemental: XRAY – Qs & As
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Irene Gold PART 2 Supplemental: XRAY – Qs & AsWhat am I?
•Fast moving electrons collide with matter in any form, xrays are produced
•In an x ray tube this is done by directing a stream of electrons at a high speed
against a metal target
•As they interact with the atoms of the target, the electrons give up most of
their energy in the form of heat
•However about 1% of their energy is emitted as x radiation
•The X-ray tube is inside a heavily lead lined protective housing.
•The x ray tube is located within a glass envelope (Pyrex inside the tube
housing.
•The tube consists of 2 electrons called the cathode and anode ✔️Ans -
Production of X rays
What does a Cathode consists of? ✔️Ans - • Large filament
• a small filament
• focusing cup
What am I?
• Serve as the source of electrons in the production of x rays and are made of
tungsten
• Thermionic emission occurs when a current is applied to the filament, the
coil of the wire becomes very hot, boiling off electrons
• The temperature of the filament controls the quantity to electrons (mA)
emitted from it.
• The number of electrons determines the number of x rays created ✔️Ans
- The filaments (X-ray)
What am I?
• Part of the cathode and encases the 2 filaments.
• This is where thermionic emission occurs ✔️Ans - Focusing
cup/filament cup
What am I?
• Positive electrode in the x ray tube
• Most x ray tubes consist of a rotating anode
,• Rotating target receives electrons as they move from cathode to anode
✔️Ans - Anode
What am I?
• The reason for the rotating target is to dissipate the heat generated
• This exposes an area of the tungsten target of the anode and this area is
called the focal spot
• Focal spot will be determined by the size. Of filaments that is chose
• Smaller filament=better detail ✔️Ans - The rotating anode target
What am I?
• Has the effect of making the actual focal spot size appear smaller when view
from the position on the film
• The smaller the target angle, the smaller the effective spot.
• Stream of electrons narrows down to an effective beam ✔️Ans - The line
focus principle
What am I?
• Heats the filament causing a boing off of electrons ✔️Ans -
Milliamperage (mA)
What am I?
• More current=more electrons produced=more extras produced=greater
radiograph density (darker) ✔️Ans - Milliamperage per second (mAs)
What am I?
• The overall blackening on a film
• Radiolucent: structures that produce more blackening on the film
• Radiopaque: structures that produce less blackening on the film (whiter)
✔️Ans - Density
What am I?
• The relationship is directly proportional
• Changing the mAs is the primary method to control the blackening on the
film
• MAs increases= more film exposure
, • It takes a minimum change of 30% to see a minimum change in density on
film
• If the mAs is doubled the density is doubled. If the mAs is halved the density
is halved ✔️Ans - MAS and density
What am I?
• Force applied to accelerate the electrons front the cathode to the anode at
the time of exposure
• The greater the force, the greater the numbers of high energy x ray photons
will produced
• Wavelength and frequency are inversely related
• Low kVp=low energy=weak penetration
• Higher kVp produces shorter wavelengths with a greater ability to penetrate
tissue ✔️Ans - Kilovoltage (kVp)
What am I?
• The difference in density between 2 structures
• Contrast makes detail visible
• KVp controls contrast but they are inversely related ✔️Ans - Contrast
What am I?
• High contrast=short scale
• Type of film will have sharp difference in dark and light areas. A black and
white film=underexposed (bone film)
• Low kVp produces less scatter, however the amount of radiation absorbed
by pt is increased ✔️Ans - Low kVp
What am I?
• Low contrast=long scale
• Type of film shows very little differences between densities
• More shades of grey (soft tissue film)
• High kVp produces more scatter, however the amount of radiation absorbed
by the patient is decreased ✔️Ans - High kVP
What am I?
• To lower contrast-longer scale of contrast- more shades of gray you must:
increase kVp by 15% and decrease mAs by 50%
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