What does radiolucent mean?
Opaque to x-rays
Invisible to x-rays
What density is radiopaque?
Metal
Air
Are all of these labels correct?
Yes
No
What is A?
Focusing cup
Filament
Target (anode)
Rotor
What is B?
What is C?
Glass envelope
Electrons
Bearings
What is D?
What is E?
What is the heel effect?
The beam is more concentrated on the cathode side
The beam is more concentrated on the anode side
The imaginary line following the centremost part of the beam
The imaginary line following the outermost part of the beam
What is the central ray?
An imaginary line following the centremost part of the beam
An imaginary line following the outermost part of the beam
Controlling the size of the beam is a legal requirement
Keeping the beam large makes the image sharper
If a smaller volume of tissue is irradiated, is a smaller or larger scatter generated?
Smaller
Larger
Is scatter desirable?
Yes - it causes sharpness of the image and decreases the patient's radiation dose
No - it causes unsharpness of the image and increases the patient's radiation dose
What structure controls the beam?
Collimator
Grid
How does a collimator work?
Reflects/absorbs the x-rays
Concentrates the beam
Where should the patient be placed in regards to the Bucky and tube?
Close to the Bucky, far away from the tube
Far away from the Bucky, close to the tube
Close to the Bucky, close to the tube
Far away from the Bucky, far away from the tube
What is true regarding the beam passing through the patient?
Some x-rays are absorbed and stop their travel
Some are scattered and continue to travel
All scattered x-rays continue to travel in the correct direction
A remnant beam exits the patient
The remnant beam is accompanied by any scatter travelling in a similar direction
All scattered x-rays will accompany the remnant beam
What are correct facts regarding the Bucky?
It is placed immediately in front of the patient
It has a tray to hold the receptor
It has a grid to allow as much scatter as possible to reach the receptor
It has a grid to prevent as much scatter as possible from reaching the receptor
There are different types of grids
Bucky
Receptor
What is the grid ratio?
Relationship between the height of the lead strips and the width of the spaces between them
Relationship between the weight of the lead strips and the width of the spaces between them
How are the strips placed in a non-focussed grid?
Parallel
Angled - matches angles of the x-rays exiting the patient, must be used with the tube at a specific distance away
Moving - increases efficiency and hides any lines that may be caused by the grid material
How are the strips placed in a focussed grid?
How are the strips placed in a reciprocating grid?
What are the correct facts regarding receptors?
Device used to capture the remnant beam
Device used to capture the scatter beams
Can be a film or digital system
What are correct facts regarding film receptors?
A single piece of film is supported in a cassette
A film is typically one-sided
There is an intensifying screen on one side of the film
The film needs to be processed in a darkroom so the image becomes visible
What are correct facts regarding a digital receptor?
A single sided receptor array supported in a cassette
There is also a filament in the cassette
The image has already been processed electronically
The latent image is formed directly on the receptor, which reacts to the x-ray beam
With either film or digital, you end up with an image which can be viewed on either a light box (film) or computer screen (digital)
What is the kVP (kilovolts peak)?
Controls the penetrating power of the x-ray beam
Controls the number of electrons crossing from the cathode to the anode
The time that the electrons are allowed to cross the tube for
What is the mA (milliamperes)?
What are x-ray factors expressed in?
kVp
mA
s
Where is the x-ray created?
Anode
Cathode
How fast does a rotating anode spin per minute?
3400 revolutions
3000 revolutions
3200 revolutions
3600 revolutions
Why does the anode spin?
Reduces wear
Spreads the load on the anode
Allows lower tube currents
Allow shorter times
What facts are correct regarding Bremsstrahlung?
The x-ray beam is heterogeneous
The energy of the Bremsstrahlung x-ray will vary depending on how far an electron penetrates a target atom
The energy of the Bremsstrahlung x-ray will vary depending on how quickly an electron penetrates a target atom
X-rays of a single energy will be produced
kVP controls the range of energies produced
mA controls the range of energies produced
Interactions in the outer part of the atom generate weaker x-rays, the inner part is stronger
Interactions in the outer part of the atom generate stronger x-rays, the inner part is weaker
X-ray Bremsstrahlung comprises a range of energies from an identifiable maximum to an indeterminate minimum
How do you control Bremsstrahlung?
kVp controls the maximum energy within the beam
kVp controls the minimum energy within the beam
mA and s control the number of photons of energy within the beam
mA and s control the penetration rate of photons within the beam
What are the two major parts on the cathode side of the tube?
Filament and focusing cup
Filament and bearings
Bearings and rotor
Rotor and focusing cup
What does the filament release when it's heated?
Cloud of electrons (thermionic emission)
Cloud of protons (thermionic emission)
Cloud of atoms (thermionic emission)
Is the focusing cup positively or negatively charged?
Positively
Negatively
Why does the focusing cup condense the electron cloud?
Encounters a smaller area of the target
Encounters a larger area of the target
What directions are Bremsstrahlung radiation produced?
All directions
Forwards
Backwards
Laterally
What is the only part of the beam required?
Beam travelling towards the patient
Beam travelling away from the patient
Beam travelling upwards through the patient
Beam travelling downwards through the patient
Why is there an oil filled space between the housing and the tube?
Absorbs the heat that is produced
Reduces the scatter
Decreases the amount of electron penetration
Decreases the number of electrons of energy in the beam
What is the role of the collimator?
Improves quality of the image
Limits the beam
Not a legal requirement
Desirable
If the beam is restricted, is the scatter radiation increased or decreased?
Increased
Decreased
What are correct facts regarding scatter?
Restricting the beam reduces scatter
Restricting the beam increases scatter
Reducing scatter radiation improves image quality
Reducing scatter radiation reduces image quality
Restricting the beam reduces the patient's radiation dose
Restricting the beam increases the patient's radiation dose
What is scatter often referred to as?
Compton scatter
Compton electron
Recoil electron
Where can the outer shell electron gain some energy from and what does it become?
Photon - becomes recoil/Compton electron
Neutron - becomes recoil/Compton electron
Electron - becomes Compton scatter
Photon - becomes Compton scatter
What happens to the x-ray photon when it collides with an outer shell electron?
Retains the remainder energy, but changes course (scatters) in a random direction
Increases its energy, but changes course (scatters) in a random direction
Decreases its energy, but changes course (scatters) in a random direction
Does the kVp value have a direct effect on scatter, regarding amount produced and direction of scatter?
Does a collimator compress and focus the x-ray beam?
A collimator works by 2 pairs of lead leaves which absorb or reflect the x-ray beam
Does a low kVp increase or decrease the scatter formation?
Decrease
Increase
If there is less scatter, how does the image look?
Less image
More image
What is needed to to counteract the less image?
More mA's
Less mA's
Why can a high mA be bad for a patient?
Higher patient dose
Produces more scatter
Decreases clarity of the image
What does a high kVp affect?
Contrast
Sharpness
What is good contrast?
Black
White
Grey
Low kVp
High kVp
What is optical density?
Overall darkness of the image
Overall lightness of the image
How do you maintain optical density?
Balance of kVp and mA is needed
kVp controls penetration
mA controls the colour of the image
What do you increase the kVp by to double the optical density?
10%
15%
20%
5%
What do you increase the mA by to double the optical density?
100%
80%
120%
90%
What are correct facts regarding the control panel?
Allows you to set kVp, mA and s
Allows upright v recumbent grids to be selected
Allows exposure to be made
Allows AEC (Automatic Exposure Chamber) and exact chamber to be selected
How many target sizes are there?
1
2
3
4
What size target is used for smaller exposures?
Smaller target
Larger target
What are correct facts regarding target size
Appropriate target sizes are used to avoid overheating the target material
The target size affects the quality of the image
The smaller target produces a larger penumbra around the image - causing it to looked blurred
The larger target produces a larger penumbra around the image - causing it to looked blurred
The larger target is used for smaller exposures
There are commonly 5 targets in an x-ray tube
The penumbra increases as the subject-receptor distance decreases
The penumbra decreases as the target-subject distance increases
The distance between the target and the subject, and the subject and receptor will affect the image
What is the subject-receptor distance also known as, and what size is desirable?
Object-image distance (OID) - small
Object-image distance (OID) - large
Source-image distance (SID) - small
Source-image distance (SID) - large
What benefits does a small OID give?
Reduces magnification
Geometric unsharpness
Reduces penumbra effect
Lower energy x-ray photons to dissipate
Allows the beam to be more homogenous
What distance is desirable for the Source-image distance (SID)?
Long
Short
What benefits are there with a long SID?
Allows the lower energy x-ray photons to dissipate
Makes the beam more homogenous
Geometric un-sharpness
Is distortion undesirable in an x-ray image?
Why does distortion occur?
When there is too much energy penetrating the patient
When the anatomy lies at an inappropriate angle to the receptor, or vice versa
What factors make an x-ray optimal?
Collimate the beam to the relevant anatomy
Select a large target size
Have a short OID
Have a long OID
Have a short SID
Have a long SID
Selecting kVp to allow adequate penetration
Selecting mA ensuring enough photons get through the subject
Consider anatomy to the receptor
Ensuring balance of kVp and mAs to a suitable level of contrast
How can the Bucky be placed?
Vertically
Horizontally
Diagonally
What facts are correct regarding the Bucky?
Designed to hold a receptor
There is only one type of Bucky
It cannot be moved into various positions
It holds an anti-scatter grid
It holds the receptor close to the grid and the grid close to the protective front plate
It can contain automatic exposure chambers
What is the role of an anti-scatter grid?
To eliminate as much scatter as possible as it exits the patient and before it reaches the receptor
To eliminate as much scatter as possible as it enters the patient
To focus the scatter before it reaches the receptor
To decrease the amount of radiation to the patient
Height divided by the interspace thickness
Number of grid strips per centimetre
What is the grid frequency?
What type of lines does a linear grid have?
Diagonal
Criss-cross
Where is a linear grid most efficient?
At the central section of the grid
At the outermost section of the grid
Over the whole grid
What is the cheapest and easiest grid to make?
Linear/parallel grid
Focused
Crossed
Static
Moving/reciprocating
What type of grid has angled strips?
Linear/parallel
Which portion of the grid matches the direction of the beam?
Whole grid
Centre portion of the grid
Outermost portion of the grid
What is the aim of a reciprocating grid?
Blur the shadows of the grid strips so they're not visible on the image
To decrease the amount of radiation
To improve the contrast of the image
What types of strips can a reciprocating grid have?
Why are crossed grids commonly found in general radiography practice?
They are extremely effective at scatter removal, as they're made up for 2 grids running at 90 degrees to each other
They are extremely effective at scatter removal, as they're made up for 4 grids running at 90 degrees to each other
They are the cheapest form of imaging
Difficult to use as the central part of the beam must be perpendicular and central to the grids
Why is an air gap beneficial instead of a grid?
Reduces the dose
Decreases the time exposed to the radiation
The image becomes clearer
What does the cassette hold close together?
Intensifying screens and film
Film and filament
Receptor and grid
Glass envelope and bearings
What do the phosphors act as in the intensifying screens?
Amplifiers - they convert the x-rays into visible light which then interacts with the film
Depressors - they convert the x-rays into visible light which then interacts with the film
What does the phosphor layer contain?
Crystals - image obtained depends on the size of these crystals
Protons - image obtained depends on the amount of these protons
What is spectral matching?
The emulsion is set to match the colour of light being emitted by the intensifying screens
The base is lightly tinted (pale blue or grey) to match the colour of light being emitted by the intensifying screens
Silver halide crystals are active in the emulsion
The emulsions are covered by a fine, translucent protective layer
A digital receptor has intensifying screens or film and an area for patient information
What facts are correct regarding digital receptors?
Cassette is a rigid, light-tight and dust-proof support
There is an area for patient information
There is a single sided imaging plate
There is a double sided imaging plate
The latent image is still invisible and needs to be processed
What is the order in an intensifying screen?
1) Protective coating 2) Phosphor (emulsion) layer 3) Reflective layer 4) Base
1) Protective coating 2) Reflective layer 3) Phosphor (emulsion) layer 4) Base
What is the base made of?
Strong, flexible, chemically inert material (e.g. plastic)
Weak, flexible, chemically inert material (e.g. plastic)
Strong, solid, chemically inert material (e.g. plastic)
Weak, solid, chemically inert material (e.g. plastic)
The higher the speed, the more re-active the screen is
What layers does the x-ray beam pass through?
Base
Reflective layer
Protective layer
Phosphor layer
Does the x-ray beam interact with the phosphor layer to emit light?
Why do the phosphors have a high atomic number?
So the x-ray absorption is high
So the x-ray absorption is low
So the light emitted from the x-ray beam is high
So the light emitted from the x-ray beam is low
What is the x-ray conversion efficiency?
Large amount of light per absorption of x-ray photons
Small amount of light per absorption of x-ray photons
How much afterglow is optimal?
Maximal
Minimal
Should the phosphors be affected by heat, humidity or any other environmental effects?
What do the emulsion layers of the intensifying screens contain that react to x-rays?
Crystals
Protons
Light waves
What size crystals produce finer, more contained light?
Small
Medium
Large
What needs to happen in screens with small crystals?
More exposure to produce the same amount of image than screens with larger crystals - more dose
Less exposure to produce the same amount of image than screens with larger crystals - less dose
Where are fine crystal screens most commonly used?
Areas away from the torso
Lumbar spine
Pelvis
Thoracic spine
What direction is light emitted from the phosphors?
What is the role of the reflective layer?
Redirects the light emitted from the phosphors, so as much light as possible is travelling towards the film
Redirects the scatter away from the receptor, so a minute amount of scatter is travelling towards the film
What percentage of the image is formed by the direct interaction of x-rays with the film?
1%
70%
50%
What is the role of the protective layer of the intensifying screen?
Fine translucent layer to protect the phosphors from dust and abrasion
Thick translucent layer to protect the phosphors from dust and abrasion
Fine coloured layer to protect the phosphors from dust and abrasion
What is the active ingredient in the emulsion of a film?
Silver halide crystals
Gold halide crystals
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