RQ3
what factors are associated with subject contrast?
1. patient thickness
2. mass density of tissue
3. atomic number of anatomical shape
4. shape of anatomy
What are the best way to minimize magnification?
long SID and short OID.
What does increasing your SID do?
1. decreases magnification
2. decreases beam intensity
3. increases spatial resolution
what exposure factor combination reduces quantum mottle?
high mAs, low kVp, slow IR
how does patient thickness affect image quality?
1. decreased contrast
2. increased focal spot blur as thickness increases
3. increased distortion/increased magnification
4. OID increases
What are the two types of shape distortion?
1. elongation
2. foreshortening
Where is focal spot blur the greatest?
the cathode end.
what formula/law do you use to maintain RE while increasing your SID?
the direct square law
what is the order of tissue increasing density?
air, fat, water (soft tissue), muscle, bone.
A high quality image should have_______?
minimal magnification
Which focal spot will give you the greatest spatial resolution?
small focal spot
when trying to see bony detail on a radiograph, which focal spot should you use?
small focal spot.
how do you reduce motion blur?
1. patient instruction
2. short exposure time
how is spatial resolution related to SID.
directly related.
SID increases= spatial resolution increases
SID decreases= spatial resolution decreases
what is a Colle's fracture?
displaced fracture of the distal radius with a posterior dislocation.
what happens when a body part is angled with a perpendicular CR?
foreshortening.
what causes distortion?
1. object position
2. object thickness
3. object shape
define spatial resolution.
the ability to distinguish detail of small objects with high subject contrast.
what happens with increases IR speed?
1. increased noise
2. decreased spatial resolution
3. increases quantum mottle
4. decreased contrast
what is a Greenstick fracture?
incomplete fracture, fracture that does not go all the way through the bone. most common in children.
what is the definition of the anode heel effect?
variation of beam intensity due to absorption of x-rays in the anode, on the longitudinal axis.
1. increase SID
2. decrease OID
3. use smaller focal spot
why does focal spot blur occur?
because the beam does not come from a point source, instead it comes from a rectangular source that diverges.
what happens with increased OID?
1. increased magnification
2. increased size distortion
3. elongation and foreshortening
what is a Boxer fracture?
fracture of the 5th metacarpal.