Sciences Unit 2 SG Flashcards
What things must we consider every time we image a pt that may effect technical factors?
(7)
Body habitus Age Gender Pathos Race Tissue amt Contrast mediums
If z# is increased, what happens to attenuation and density?
A=I
D=D
If tissue density is increased, what happens to attenuation and density?
A: I
D: D
If part thickness is increased, what happens to attenuation and density?
A:I
D:D
If + contrast is increased, what happens to attenuation and density?
A:I
D:D
If - contrast is increased, what happens to attenuation and density?
A:D
D:I
5 additive pathos
Pulmonary edema Cirrhosis Osteoarthritis Abcess TB
5 destructive pathos
Bowel obstruction Pagets Osteoporosis Osteomalacia Pneumothorax
What specific change is needed for post mortem images
Increase mA 25-50%
What specific change is needed for pulmonary edema?
Increase 5-15% kV
What specific change is needed for pt with muscle atrophy
Decrease mA 25-50%
What specific change is needed for pt with osteoporosis
Decrease kV 5-15%
What specific change is needed for increased pt thickness
2x mA for every 4-5 cm over/under ave
Why do additive pathos usually require an increase in kV
More minerals, denser tissue, sometimes thicker body part
Why do destructive pathos require less kV
Size or thickness
Why does bone increase attenuation
Bone has highest density, more minerals, harder for photons to pass through
Why does muscle increase attenuation
Muscle had high water content
Why do elderly generally result in decreased attenuation
Decrease in muscle, bone density, thickness
Increase in easier to penetrate fat
What is HVL of human tissue, when and how do we change technique based on this
4-5 cm, reduce or add 2xmAs for every 4-6 cm
Relationship between differential absorption and subject contrast
Differential absorption effects subject contrast directly
Specific example of subject distortion and how do we overcome it
LSS apophyseal joints. We angle pt so beam is perp because joints sit obliquely
Provide a specific example of subject distortion and how we overcome this during positioning
Spine/KUB with large patient, increased OID, decreased detail
Describe the difference in the location of ionization chanbers vs the older phototiers within the table assembly
Old: under cassette
New: above IR
Describe what happens to the exposure time when using AEC and decreasing kVp
increase time
Describe what happens to the exposure time when using AEC and increasing mA station used
Decrease time
Describe what happens to the exposure time when using AEC and collimating too tightly so it cuts off a photocell
increase time
Why is backup time significant in a modern AEC unit? What do we have to assure regarding our time setting when using AEC and what happens if we don’t
- Prevent tube from overheating/damaged, over exposure to pt
- 150% of manual anticipated time
When is it acceptable to use the “density” setting
only use for temporary equipment problems or unusual pathos
What are the government requirements for mAs using AEC
Exposure terminated at 600 mAs
List 2 specific projections that are best performed without the use of AEC and briefly describe why they are best performed with out
AP humerus, it’s thin and won’t cover photocell, will be very underexposed
AP Cspine, very thin bone won’t cover photocell
What is average AP and Lateral abdomen measurements
AP: 22cm
Lat: 30cm
What happens to attenuation when you increase atomic density/number
increase
What happens to attenuation with increased density
increase
What happens to attenuation with increased pt thickness
increase
