X-Ray Physics Flashcards
The cathode consists of:
A large filament, small filatment and focussing cup
What is thermonic emission?
When current is applied to the filament, leading to the burning off of elections at the coil of the filament
Where does thermonic emission occur?
Focussing cup
Reason for the rotating anode target
Dissipate heat and also allow for an exposed area called the focal spot
The focal spot is determined by the:
Size of the filament (Smaller filament = finer detail)
mAs repesents:
The number of x-rays being produced
It takes a minimum change of ___% to see a minimum change in density of the film
30
If the mAs is doubled then the density is:
Doubled
Higher kvP produces _______ wavelengths
Shorter
Lower kVP produces ______ scatter
Less
Low kVP = ______ contrast
Higher
Higher kVP creates ____________ contast
Low (10,000 + shades of gray)
An increase in kVP of 15% = _____ MAs by _____ %
Decrease by 50% (1/2)
A decrease kVp by 15% = ______ MAS by ______
Increase by 100% (2x)
How will gas, fat, muscle, soft tissue, water, bone and metal appear on x-ray
-Black: Gas/Fat
-Grey: Soft tissue, muscle and water
-White: Bone, Metal
Anode Heel Effect: # of X-Rays
-Anode: Less
-Cathode: More
Anode heel effect: Size of focal spot
Anode: Smaller
Cathode: Larger
Anode Heel Effect: Detail
-Anode: More Detail
-Cathode: Less Detail
What side would you use for a thicker body part
Cathode
As you increase the FFD, the image gets:
Smaller and clearer
If a 40” FFD is doubled to 80” FFD then the intensity of the radiation is ____ of the original
1/4
Intensifying Screens: Large vs. Small Crystals
-Large: Faster w/ less detail, higher contrast, short scale (less patient exposure)
-Small: Slower w/ more detail, low contast and long scale (more patient exposure)
Blurry halo part of an image that is unsharp
Penumbra
What causes penumbra?
-Having the tube too close to the film (short FFD)
-Having the patient too far from the film (long OFD)
-Having too big of a filament with the cathode
What test is best for screen film contact?
Wire mesh test
