Principles of Radiography Flashcards
List 4 properties which add to the dangers of x-rays.
- Invisible
- Painless
- Latent effects (delay)
- Cumulative (many small doses= large dose)
State 5 signs of direct changes in body tissue soon after exposure.
- Skin redenning/cracking
- Blood disorders
- Baldness
- Cataracts
- Digestive upset/dehydration
Describe the term Carcinogenic effects
Tumours develop in exposed tissues
Describe the term “genetic effects”
Mutations induced in the chromosomes of germ cells due to exposure of the gonads
List the three potential sources of radiation
- Tube head
- Primary Beam
- Horizontal x-rays
Describe the term maximal permissible dose (MPD)
The amount of radiation to not constitute a greater risk to health than other occupations
What is the MPD for lens of the eye for trainees under 18 years
45 mSv
When may an RPA not be necessary within general practice
If the practice complies with health and safety conditions
List 4 instructions regarding the care and wearing of a dosimetry badge
- Wear at waist level in middle of anterior abdomen
- Keep dry when not in use
- Never wear badges outside veterinary practice
- All badges to be changed at recommended time
Describe the Local Rules
- Set of instructions drawn up the Radiation Protection Advisor (includes machine/equipment information, restraint methods and precautions to take if manual restraint is necessary
- Must include the ‘Written Systems of Work’
Give two examples of rapidly dividing cells.
- The gonads
- Foetus
If a dosemeter is giving a reading of 0.5mSv or more what should you do?
- Investigate further
- Phone for advice
What is the natural radiation dose received annually?
2.2 mSv
Should pregnant employees be allowed to participate in radiography?
No
State the main ingredient of Developer.
Phenidone hydroquinone
Describe the action of Developer and name the process.
Converts exposed silver halide crystals to black metallic silver in a process known as REDUCTION
What is the ideal temperature for developer to function properly.
20 degrees Celsius
State the primary function of Fixer.
It clears the unexposed silver halide crystals from the film
Explain the term “tanning”
A process where fixer hardens the film emulsion to prevent it from being scratched when being handled
What is the function of accelerators within the Developer.
Accelerators are chemicals that increase the activity of the developer
List the 5 basic steps of film processing
- Developing
- Rinsing/stop bath
- Fixing
- Rinsing
- Drying
State the function of the rinse bath.
- Stops the development process
- Rinses the developer from the film
- Prevents carryover contamination to the fixer
Describe the methods of recognising exhausted chemicals
- the colour of the developer is an indicator it turns a brown to green colour when it needs to be changed
- underdevelopment of films
- unlikely to be fit for use after three months
- The fixer needs to be changed if the clearing time is greater than 2 - 3 minutes.
State the two primary advantages of automatic processing.
- Saves time and effort
- Produces a dry radiograph that is ready to interpret in a short space of time
State the 2 methods of film identification
- Light marker
- pencil
What is the name of the substance used to top up the developer when the level falls?
Replenisher solution
What can happen to developer if the lids is not put back on the tank during manual processing?
Process of oxidation which will result in underdevelopment of films
How often should you change developer?
Every 3 months
How long should the film be immersed in developer?
3-5 minutes
How long should the film be immersed in developer?
3-5 minutes
What will happen if left in the developer too long?
Some of the unexposed silver bromide crystals are converted to black metallic silver as well, causing uniform darkening of the film
Name the 6 main ingredients of the developer solution?
- Developing agents
- Accelerators
- Preservatives
- Restrainers
- Hardeners
- A solvent
The colour of the developer is an indicator that it needs to be changed, what colour does it change to?
-Brown to green colour
Is developer acidic or alkaline?
Alkaline
What is the main constituent of fixer?
Sodium
Describe the following terms:
.• Density
• Contrast
• Density
- The degree of blackening of the film
• Contrast
- The difference between the varying shades
Describe the following terms:
.• Density
• Contrast
• Density
- The degree of blackening of the film
• Contrast
- The difference between the varying shades
State the two factors that determine density.
- Kv
- mAS
Name the four main faults related to processing
- Underdeveloped
- Overdeveloped
- Overexposed
- Underexposed
Explain how you would differentiate using metal markers in relation to overexposure and overdevelopment of films.
- OVEREXPOSURE: stays white
- OVERDEVELOPED: darkened
If a film is described as soot and white wash what does this tell us?
Very high contrast, low kV: white image with a black background with a few shades of grey
Describe a film if the kV is too low.
The film will appear very black and white
- What does the following indicate on a x-ray film?
- Black patches
- Grey patches
- White patches
- Black tree like structure looks like lightening
- Black patches – Developer splashes
- Grey patches – Water splashes on film or chemical splashes on intensifying screens
- White patches – Fixer splashes
- Black tree like structure looks like lightening- Static
- What does the following indicate on a x-ray film?
- Black patches
- Grey patches
- White patches
- Black tree like structure looks like lightening
- Black patches – Developer splashes
- Grey patches – Water splashes on film or chemical splashes on intensifying screens
- White patches – Fixer splashes
- Black tree like structure looks like lightening- Static
Explain the production of x-rays within the tube head.
Within the tube head there is a Cathode –ve & Anode +ve.
The Cathode (-ve) consists of a filament made up of tungsten.
This filament is heated by an electric current which produces electrons.
These electrons are released by THERMIONIC EMISSION.
The electrons are directed by the focussing cup to the Anode.
The electrons travel at high speed across the tube from the Cathode which is negatively charged to the positively charged Anode (Target Area).
Electrons hit the target area and X-rays (1% ) and heat (99%) are produced.
State three main differences in relation to automatic processing to manual processing.
- increase in temp
- rinse section is missed after developer
- requires more water
Common manual film faults are described below, clearly state the cause of such faults.
- Yellow radiograph
- Air bubble
- Fingerprints on film
- Dark marks on film
- Grey marks on film
- Finger crescent
- Very dark and white film (high contrast)
- Very pale and light film : can see finger behind film
- Film very dark all over
- Yellow radiograph – incomplete washing of film – common during fixation
- Air bubble – insufficient agitation
- Fingerprints on film – dirty finger
- Dark marks on film – developer splashes on film prior to processing
- Grey marks on film – water splashed on film prior to processing
- Finger crescent – damage to the film in a rush
- Very dark and white film ( high contrast) – too low a Kv
- Very pale and light film : can see finger behind film – underdeveloped
- Film very dark all over – too high kV overexposed
State when a grid would be used whilst imaging.
When an area of interest is over 10cm
State the difference between computed radiography and direct radiography
Direct radiography uses a cassette that links straight to the Computer
Computed radiography uses a special cassette that needs to be placed in a reader for processing.
Give 2 reasons for underdevelopment.
low temp
not developed for long enough
Give 2 reasons for underdevelopment.
low temp
not developed for long enough
What is the lead lining?
- Inner case made of lead
- Surrounds tube head ensuring x-rays don’t escape as the lead case absorbs any radiation
What is the glass envelope?
-A glass vacuum that contains the Anode and Cathode of the x-ray tube
What is the vacuum?
- Space where all air/gasses have been extracted
- Allows the electrons/x-rays to travel in a straight line (if air/gasses present, electrons/x-rays would bounce off the particles and be misdirected)
What do cooling fins do?
Disperse the heat
What is the focusing cup?
- Recess where the filament lies
- Directs the electrons towards the Anode
What is the filament?
- Part of the cathode
- Made of tungsten
- Part of a low-energy circuit in the Cathode
- When heated it releases electrons from their orbit
What is the anode?
The tungsten target
What does the copper stem do?
Acts as a conductor of heat and draws the heat away from the tungsten target
What does the oil do?
Transfers heat away from the Anode
What is the aluminium filter?
Flat sheet of aluminium covering the window which absorbs any soft x-rays
What is the cathode and what happens here?
Formed of a tungsten filament
Current passed through the filament causing it to heat up
Causes electrons from the filament particles to be released - thermionic emission
What happens during electron transmission?
On activation of the exposure button a voltage (kV) is applied across the cathode and anode
Electrons are ‘fired’ across the vacuum from the cathode to the anode
What is the anode and what happens here?
Formed of a tungsten target
Positively charged to attract electrons from the cathode
As electrons hit the target x rays are produced (1% x rays 99% heat energy)
Why is the target angled?
Target is angled to ensure x rays are directed out of the tube head through the window
By how many degrees is the target angled?
20 degrees
What does the kV (voltage) affect?
The speed of the electrons travelling from the cathode, and therefore the energy of the x rays produced
What does the mA (current) affect?
The number of electrons released, and therefore the number of x rays produced
What does the exposure time affect?
The length of time of exposure affects how long the electrons are released for and therefore the number of x rays
Is the cathode -ve or +ve?
Negative
Is the anode -ve or +ve?
Positive
What is the actual focal spot?
The area of the target which the electrons strike (the area in which heat is produced).
What is the effective focal spot?
The angulation of the target means that the x-ray beam appears to originate from a much smaller area
What is X-ray output limited by?
The amount of heat generated at the target
In which machines would there be a stationary anode?
Low powered portable machines
What machines would you find rotating anodes in?
Larger, more powerful machines
What is the benefit of a rotating anode?
More efficient at removing heat
What is the collimation device called and what does it do?
Light beam diaphragm
Controls size of x-ray beam
How do you clean a casette?
Once a month (depending on caseload)
Clean from the inside out using circular motions
Use mild soapy water or a specially made cleaner
Leave upright to dry
Label casette with initials, date cleaned
Load new film in to casette.
What is a developer?
A chemical solution that converts the latent image on a film to a visible image
Converts the exposed silver halide crystals to black metallic silver
The process is known as reduction and the developer acts as a reducing agent
What step follows developing?
Rinsing
Describe rinsing.
Stops the developing process
Rinses the developer from the film
Prevent carryover contamination to the fixer
How long does the first rinse stage last for?
10 - 30 seconds
Describe the rinsing stage.
Clears the unexposed silver halide crystals from the film
Hardens the gelatin coating so that it is less easy to damage
Should take twice the amount of time as developing
Why must the unexposed silver halide crystals be removed during fixing?
If the unexposed silver crystals were to remain on the film they would discolour and darken with the exposure of light.
What temperature may staining occur during fixing?
If the fixer is above 21 degrees Celcius
Which 2 chemicals may be present in fixer solution that dissolves unexposed silver halide?
Sodium
Ammonium thiosulphate
Describe the second rinsing stage
Films should be washed in circulating water so that both surfaces of the film receive freshwater continuously
In MANUAL processing the average suggested wash time is 20 -30 minutes with periodic agitation or water circulation
In AUTOMATIC processing the water system of the processor keeps a constant flow of temperate water through and around the wash rack and film
Describe the drying stage.
The usual method is to clip the films to a taut line over a sink taking care that they do not touch each other.
The atmosphere should be dust - free with a good air circulation.
Drying frames and warm - air drying cabinets are also available and are useful if film throughput is high.
What’s the difference between a non-screen film and a screen film with regards to processing?
Emulsion on non - screen film is thicker than that of screen film
It takes longer for the developing and fixing chemicals to penetrate the emulsion and act on the silver halide crystals
Development time should normally be increased by about one minute and clearing time in the fixer will be several minutes longer.
List the differences between manual and automatic processors.
Automatic uses more water
Automatic is faster and only has 4 steps (rinse stage after developing stage is omitted)
Automatic runs at a higher temperature
What’s the difference between computed and direct radiography?
Computed radiography needs a special casette which is then placed in a reader
The image in direct radiography is sent straight to the computer
What’s the difference between computed and direct radiography?
Computed radiography needs a special casette which is then placed in a reader
The image in direct radiography is sent straight to the computer
