X-ray Tube And X-ray Production Flashcards
What are x-rays?
They’re a type of short wave length, high energy, that can penetrate matter.
What type of wavelength do x-rays have?
Short wave lengths
What can x-rays do to human cells?
They can damage them
What are the non-ionising radiations?
(4)
Radio waves
Microwaves
Infrared radiation
Visible light
What are the ionising radiations?
(3)
Visible light
UV light
Gamma rays
What does the ALARP principle stand for?
As
Low
As
Reasonably
Possible
What does the ALARP principle say?
(4)
We should weigh the risk vs benefit of the x-ray to the patient
We should get things right the first time
Optimise the radiation dose
Learn the essentials for each body part
What does the ALARP principle say in relation to repeating x-rays?
It says that we should try to get the image right the first time, but if the first image doesn’t show what needs to be shown, then a repeat is justified
What does there need to be the right amount of in order to produce an x-ray?
(2)
X-rays
Energy
What does kVp stand for?
Kilovoltage peak
What does mAs stand for?
Milliampereseconds
What is the kVp?
The energy of the beam
What is the mAs?
The amount of x-ray photons
What’s a good way of remembering what kVp is?
KVp is how hard you throw your beans
What’s a good way of remembering what mAs means?
MAs is how many beans are in your hand
What are the features of kVp?
(2)
Larger energy (kVp) is needed for larger body parts
It affects the contrast on the image
What are the features of the mAs?
(3)
It shows the current flowing from the cathode to the anode
It shows the duration of the patient’s exposure to the beams
It affects the density of the image
What does kVp and MAs both affect?
(2)
Radiation dose
Quality of image
Which direction does the current flow through in the anode and cathode?
The current flows from the cathode to the anode
What is the potential difference?
Negative towards positive charge
(-) (+)
What does the contrast of the image mean?
How many beams have penetrated through the the patient’s body to produce the image
How does the image look like if it has a high contrast?
Very black and white- over saturated
How does the image look like if it has a low contrast?
Very grey- very difficult to see any details
How does it look like if the image has an optimum contrast?
Perfect saturation- the beams have penetrated through
What is the density of the image about?
The amount of x-rays that penetrate the body
What does it mean if an x-ray image is white?
The object that shows up as white has stopped the x-ray from penetrating, e.g. metal
What is attenuation?
Energy being lost due to interactions in its path (the absorption of x-rays)
What does having a high attenuation mean?
Lots of x-rays are absorbed, so less energy is lost
What does having a low attenuation mean?
A small amount of x-rays are absorbed, so more energy is lost
What are examples of materials that have high attenuation?
(2)
Metal
Bones
What are examples of materials that have low attenuation?
(2)
Air
Lungs
What does SID stand for?
Source
Image
Distance
What does SID mean?
It means how far away the x-ray tube is from the detector
What is SID also known as?
FFD (film focus distance)
What does FFD stand for?
Film
Focus
Distance
What is the SID for most skeletal imaging?
100-110cm
What is the SID for a chest x-ray?
180cm
Why is the SID 100-110cm for most skeletal imaging?
It makes sure that the x-ray tube is far enough away that there’s no radiation burns caused on the patient
Why does the body part need to be next to the detector?
To prevent unsharpness, unclear and pixilated images
What does SOD stand for?
Source
Object
Distance
What does SOD mean?
It means the distance of the body part to the detector
What does a small SOD cause?
An unsharp image
What 2 pieces of equipment are used for imaging larger body parts?
Grids
Bucky mechanism
Where are grids and Bucky mechanisms put?
Between the patient and the detector
What do grids and the Bucky mechanism do?
They capture any scattered x-rays and electrons before they get to the detector, and then they produce an image from that
What are the advantages of grids and Bucky mechanisms?
(2)
They reduce scatter
They improve image quality
What is the disadvantage of grids and Bucky mechanisms?
They use higher doses of radiation
Between grids and Bucky mechanisms, which is stationary and which moves inside the table?
Grids are stationary
The Bucky moves inside the table or upright stand
What does AEC stand for?
Automatic
Exposure
Chambers
Where is the AEC located?
Between the patient and detector
What does the AEC do?
It works out what the exposure factors should be at a given kVp.. This causes the radiation to cut off once the detector has received a certain density and radiation level
What type of body parts are AEC used on?
Larger body parts
What are the sizes of a small detector?
24cm-30cm
What are the sizes of a big detector?
35cm x 43cm
What are the sizes for a square detector?
43cm x 43cm
What does LBD stand for?
Light
Beam
Diaphragm
What is the LBD?
It’s where the middle of the x-ray beam is aimed, so it’s the field of view that we’re exposing the patient to
What is collimation?
The size of the field we’re irradiating (giving radiation to), so it limits the area we’’re giving radiation to
What are the advantages of collimation?
(3)
It reduces the dose of radiation given to the patient
It improves the image quality
It reduces scatter
What does it mean if we use collimation on a smaller body part?
A lower dose of radiation is used, and a better quality image is produced
What do anatomical side markers do?
They indicate the left or right side of the patient
Why are anatomical side markers important?
Images can be flipped, so it makes sure that the correct side of the body has been imaged, e.g. ensure that the right wrist is imaged- not the left one by mistake
What are the type of anatomical side markers we can have?
Lead
Pb
Why is lead good in anatomical side markers?
Lead stops x-rays from coming through- it’s good protection
