Introduction Flashcards
(23 cards)
What are the five Roentgen signs?
Size, Shape, Number, Position, Density (opacity, structure), Function
What is kVp?
Kilovoltage peak (kVp) is the speed of electron flow across the tube.
What does increasing kVp do?
Increased kVp = increased speed when electrons hit target = greater penetration of x-rays = increased ‘blackness’.
What does decreasing kVp do?
Decreased kVp = decreased speed when electrons hit target = lesser penetration of x-rays = decreased ‘blackness’.
What is mA?
Milliamperage (mA) is the amount of current flowing through the tube.
What does increasing mA do?
Increased mA = increased amount of x-ray passing through patient = increased ‘blackness’.
What does decreasing mA do?
Decreased mA = decreased amount of x-ray passing through patient = decreased ‘blackness’.
2x mAs = _____x ‘blackness’
2
By doubling mAs, it is equivalent to a 15% _________ in kVp
Decrease
By halving mAs, it is equivalent to a 15% _________ in kVp
Increase
What is contrast?
The number of shades of gray between black and white.
A low mAs and high kVp setting is best for which study(s) and why?
Thorax (allows better imaging of soft tissues).
A high mAs and low kVp setting is best for which study(s) and why?
MSK and abdomen.
To achieve the same ‘darkness’, an increase in distance would require a concurrent increase in _________
mAs
To achieve the same ‘darkness’, a decrease in distance would require a concurrent decrease in __________
mAs
What are the six types of opacities?
- Air 2. Fat 3. Fluid 4. Soft tissue 5. Mineral/bone 6. Metal
What is summation?
When the sum total of multiple tissue’s densities appear on the radiograph (overlap).
What is a silhouette sign?
The inability to differentiate the edges of similar adjacent tissue types.
How does the distance between the object and the film affect sharpness?
The farther the distance between an object and the film, the greater the ‘penumbra’ (halo of unsharpness).
How does the distance between the object and the film affect magnification?
The farther the distance between an object and the film, the greater the magnification.
Motion is exacerbated by increased _______
mAs
pros of radiographs
cheap, fast, ubiquitous, good at spatial resolution of adjacent
cons of radiographs
poor detail due to limited contrast, radiation risk, bad at special resolution if overlapping, need 2 views
