Diagnostic Aids Flashcards
What is the tungsten?
Used as the filament and target as it has a high atomic number therefore a high number of electrons and also a high melting point.
What is the primary beam?
X-rays that emerge from the window of the tube head, usually visualised by the light beam diaphragm.
What is the actual focal point of an radiography machine?
The spot where the electrons hit the target, the target is angled at 20 degrees
What is the effective focal spot of the radiography machine?
Because the target is angled the x-ray beam that leaves the target is narrower and more defined.
What is the tube head?
Encases the anode, cathode and the light beam diaphragm
What is the tube head lined with?
Lead.
Why is the tube head lined with lead?
To absorb the X-rays that are produced in different directions to the primary beam
What is the line voltage compensator.
Will stop fluctuations in normal mains electricity
What is a stationary anode?
Limited mA can be used with this anode as it will only withstand a certain amount of heat.
What is a rotating anode?
And set into a rotary arm, constantly turning, and therefore withstand more heat
What is the KV?
The speed and energy that the electrons hit the target, also known as the potential difference.
What is the mA?
The quantity of electrons hitting the target.
What are calcium tungsten screens?
These will only emit blue light. The image is less defined.
What light does rare earth phosphorus screens?
These emit green light
What is the pro of using Rare Earth Phosphourus Screens?
Absorb more x-ray energy and are efficient at converting this energy into light.
Better defined image
Lower exposure can be used
How many layers are the sheets of an x-ray film mad up of?
Several
What is the top layer of the x-ray film called?
Known as the emulsion.
Where are silver bromide crystals found?
In the emulsion layer of the x-ray film.
What are silver bromide crystals sensitive to?
Sensitive to x-rays and white light.
What is the second layer of the x- any film?
Known as the subbing layer
What does the subbing layer of the x-ray film do?
Sticks the emulsion to the third layer (the base)
What is the super coat of the x-ray film?
A protective gelatine coating
What is a non-screen?
For use without an intensifying screen, the image is produced by x-ray energy only. High mA is require
What is monochromatic screen film?
Sensitive to blue light only
What should a monochromatic screen film be used with?
Only to be used with calcium tungstate screens as these emit a blue light only
What is the orthochromatic screen film?
Can be used with either type of screen as they are sensitive to blue and green light
What is duplitised?
- Emulsion on both sides = double efficiency
- Good contrast and blackness but reduced definition due to marginally superimposed images
What 3 things do we need to know about single-sided film?
- Emulsion is one side only
- Very fine detail image with good soft tissue and bone detail
- Need to increase exposure factors
What will a fast film and screen allow?
Lower exposures but the definition of the image will be less.
What does a slow film and screen combination require?
Higher exposure.
What are the white light filters?
Red filter and brown filter
What films do you use with a red filter in radiographs?
Use with blue/green light sensitive films
What films do you use with the brown light filter?
Use with blue light sensitive films
What is in the developer of an x-ray machine?
Alkaline Phenidone hydroquinone or metal hydroquinone
What does the fixer do?
🔶 fixer will dissolve any unexposed silver bromide known as clearing time.
🔶 preservative
🔶 hardener to prevent further softening, known as tanning
What is the developer also known as?
Known as reducing
What does this developer do?
Converts exposed crystals to of silver bromide into metallic silver
What does the developer contain?
Contains buffers to maintain alkalinity
What do the strainers in the developer do?
Limit use of reducing to exposed silver bromide only
Where are hardeners found?
Found only in automatic developing solution, will prevent excess swelling and softening of emulsion
How will you be able to tell that the developer is exhausted?
Will show as an under developed film
What is the least efficient and most basic method for producing a digital image?
Film digitisation
What is film digitisation?
The most basic and least efficient method of producing a digital image
What does film digitisation involve?
Fed through the film digitiser a device with a light source at one side if the film and a series of detectors at the other.
What is indirect radiography?
The most widespread technology employed to produce digital radiography is by computed radiography.
What is direct radiography?
Th film or plate is replaced by a detector array. Image is directly captured.
Why is direct radiography direct?
The transmitted x Ray beam strikes the surface of the detector and at this point th ima can be produced hence direct.
What does contrast radiography involve?
Involves altering the opacity of structure, its contents and the surrounding tissues to make it more visible on the radiograph
What does contrast media do?
Alters the absorption of the primary beam and improves the contrast
What is barium sulphate used for in radiography?
Used to outline the alimentary tract
What is barium sulphate?
A chalky whit powder that is mixed with water to produce a liquid suspension or paste
Why should care be taken when using barium sulphate?
It may leak into the peritoneum or if inhaled may cause adhesions or aspiration pneumonia
What are iodine compounds?
All water soluble compounds, appear as cleaner liquids.
What are iodine compounds used for?
Usually used for all examination not involving the alimentary tract unless perforation is suspected.
What are iodine compounds used for in radiographs?
Used to examine kidneys, ureters and bladder as they are water soluble.
What is radiolucent (negative) contrast media?
Decrease the absorption of the primary beam and appear black on the radiographic image
Usually air but may be oxygen, carbon dioxide or nitrous oxide
kV may need to be lowered when using air contrast
What are double contrast studies?
Positive media are used to coat any hollow structure, then air is introduced to distend the structure
Air is introduced secondarily otherwise bubbles and uneven coating may occur
The positive media will cling to the lining and the air highlights any defects
When would you use double contrast studies?
May be used in cytography and barium enema studies
What could cause a fault on the film itself?
Handling artefacts - static, fingerprints, scratches, creases
Fogging - box lid left off
Out of date film
Storage of boxes
Cheap film = poor quality emulsion
How could storing the film cause a fault?
Temperature, humidity, vertical storage
What causes faults of the screen and cassette?
Old screens
Scratches
Dirty screens - dusty, hairs in cassette
Light leakage into cassette
Poor screen to film contact - foam crumbling
Incorrect screen speed for application
What is the calculation for time and mA?
Seconds X mA = mAs = mAs - seconds = mA
What is the rule of the kv and mAs.
If the kv is increased by 10 the mAs must be halved
If the kv is increased by 10 the mAs must be doubled
How do you calculate the film focal distance?
New exposure (mAs) = old expsur (mAs) X new FFD2 / old FFD2
Kv will remain the same
How do you calculate the grid factor?
New exposure (mAs) = old exposure (mAs) X grid factor
Kv will remain the same
What are the advantages of ultrasounds?
Does not use radiation
Produces real time images
Can be used without sedation
Minimal patient preparation needed
Non-invasive, giving good visualisation of the abdominal organs
What are the disadvantages of ultrasounds?
Conor be used in areas containing large amounts of air such as lungs
Cannot be used for skeletal system
Accuracy is dependant on operator skill and experience
Requires expert interpretation of images
What areas are suitable for ultrasounds?
Abdominal organs
Reproductive organs
Heart and vascular function
Thyroid
Larynx
Tendons
Ligaments
Soft tissue masses
What is CT scanning?
Radiographic technique grater definition and differentiation between tissue types
What is CT scanning useful for?
Skeletal
Central nervous system
Tumours
A radiography demonstrating a lack of penumbra is described as what?
Having good definition
What do the initials TLD refer to?
Type of personal radiation monitor
To deuce radiographic contrast the exposure factors should be altered by?
Increasing the KV
The mAs primarily affects the?
Blackness of the radiograph
The invisible image produced in the film emulsion by exposure to radio action or light is described as the?
Latent image
What does the developer fluid do?
Converts exposed silver halide crystals to black metallic silver
What is the purpose of the aluminium filter across the window of the tube head?
Reduce scattered radiation
Where are lithium fluoride crystals found?
Thermos luminescent dose meters
What do white specks on a processed image indicate?
Dirt on the intensifying screens
When would a slow film screen combination be most useful when taking a radiograph?
On a Norfolk terriers nasal turbinates
If the kv is increased, to produce a comparable radiograph, what should happen to the mAs?
Should be halved
What are dark splash marks on the radiograph be caused by?
Developer
What should the walls Of a dark room be painted?
Whit to reflect the safe light
What is an example of a negative contrast agent?
Air
What organ do lead neck guards protect?
The thyroid
What newer imaging technique also uses x ray tube head to generate its image?
Computed tomography
What is the legal document which covers the use of radiation?
Ionising radiation regulations 1999
What is myelography?
Use of contrast agent to view spinal cord
What is arthrography?
Use of contrast agent to view joint
What is cystography?
Use of contrast agent to view bladder
What is gastrography?
Use of contrast agent to view stomach
What are protons?
Positively charged particles contained in the centre or nucleus of the atom.
What are neutrons?
Particles of similar size to protons that are also found in the nucleus but carry no electrical charge
What are electrons?
Smaller, negatively charged particles that orbit the nucleus in different planes or shells
What is the melting point of tungsten?
3380 degrees
What is the atomic number of tungsten?
74
List the 3 main types of positive contrast agents?
Barium sulphate
Water solvable iodine containing preparations
Low osmolar non ionic media
What is barium sulphate commonly used for?
Investigation of the alimentary canal
What is water soluble iodine containing preparations commonly used for?
Investigation of the urogenital system
What is low osmolar non ionic media commonly used for?
Myelography
What trim described contrast radiography of a joint space?
Arthrography
Why would a patient be given glycogen prior to a gastrogram?
Slows gastric emptying
What are very dark shades on a radiograph likely to show?
Gas
