x-rays Flashcards
Purpose of contrast radiography
To enhance visualisation of structures or organs by altering radio-opacity of structure of interest or surrounding areas.
2 positive contrast agents
- Barium Sulphate for gastrointestinal tract
- Water soluble iodine for urogenital system
What is double contrast study
Positive agent to line the cavity negative agent to distend it
Heavy sedation or GA not recommended during barium swallow due to ?
Risk of regurgitation and aspiration
How often to take x-rays for barium study?
every 15-60 mins
Contraindications for barium study?
- Risk of regurgitation
- Food withheld for 24hrs prior
- If perforation suspected use water soluble iodine
What gas is used for negative media
Room air, oxygen, co2, nitrous oxide.
What does emulsion layer of film contain
Silver bromide suspended in gelatine
What coats the surface of film
The supercoat
What function developer does, temperature, pH
Reduction, 20 for manual or 28 for automatic degrees, Alkaline
What function fixer does, pH
Clearing and tanning, acidic
What causes yellow staining of developed films
insufficient rinsing of developer
What colour is developer splash on film
Black
What colour is fixer splash on film
White
Too dark x-ray
Overexposure
Overdevelopment
Too high developer temp
Fogging
Too pale xray
Underexposure
Underdevelopment
Too low developer temp
Too dilute developer
What is soot and whitewash
High contrast - too low kV
What is flat film
Low contrast - too high kV, fogging
What causes contrast too high (soot and whitewash)
Too low kV - Increase kV
Overdevelopment - reduce developing time/temp
What causes contrast too low (flat film)
Scatter radiation - use a grid/collimate beam
Overexposure - reduce kV
Underdevelopment - Increase developing time/temp
What causes poor definition
Movement blur
Object film distance too great
Poor screen-film contact
What causes too high density
Overdevelopment
Overexposure
What causes density too low
Underdevelopment
Underexposure
What causes fogging
Scatter radiation
2 members of electromagnetic spectrum with highest frequency and shortest wavelenght
x-ray
gamma radiation
Properties of x-rays and gamma rays
- Travel through vacuum
- Speed of light
- Can be absorbed or scattered
- Medium is not required for transmission
What is atomic number ?
The number of protons possessed by the atom
Two types of anodes
Stationary anode
Rotating anode
Pros of rotating anode
Less heat in one area as the anode rotates
Allows higher exposure factors
Allows longer exposure times
Why is mylobdenum used to rotate the anode
Bad heat conductor
What angle is the target area at on a rotating anode
6-20 degrees
