Medical Imaging Flashcards
What do x-rays do to living cells?
Ionise them - damaging them
What are x-rays used for?
Medical diagnosis in hospitals
What are x-rays ?
High frequency, short wavelength electromagnetic waves
What is the same size as an x-ray wavelength?
The diameter of an atom
What happens to the waves when they move through the body?
They pass through (transmitted by) healthy tissue but are absorbed by denser materials like bones and metal
x-rays affect ……. …… in the same way as light so they can be used to take ….
photographic film, photographs
What can x-ray photographs be used for? (+2 examples)
Diagnosing medical conditions such as bone fractures or dental problems
How can x-ray images be produced electronically?
- Using what?
- What is that?
- How does this thing create the image?
- What is this technique also used for?
A Charge-coupled device (CCD)
A silicon chip divided up into a grid of millions of identical pixles
They detect the x-rays and produce electronic signals which are used to form high resolution images
Taking photos on digital cameras
What electromagnetic wave do CT scans use?
What do they produce?
x-rays
High resolution images of soft and hard tissue
What does CT stand for?
Computerised axial tomography
How does a person get CT scanned?
- Where the person is…
- Beamed…
- Detected
- Spin
They’re put inside the cylindrical scanner
An x ray beam is fired through the body from an xray tube
It is picked up by detectors on the opposite side
The x-ray tube and detectors rotate during the scan
How is the CT scan image formed?
How do you get a 3D image?
A computer interprets the signals from the detectors to form an image of a two dimensional slice through the body.
Multiple 2D CT scans can be put together to make a 3D image of the inside of the body.
What do x-rays cause that is useful to doctors?
They kills body cells if the dose is high enough so they can kill cancers, just like gamma radiation
How do x-rays have to be controlled when killing cancers so that they don’t damage normal cells? (2)
They need to be: carefully focused, at the right dosage to kill not mutate or damage
How are x-rays used to treat cancer in 3 points?
The x-rays are focused on the tumour using a wide beam
The beam is rotated around the patient with the tumour at the center
This minimises the exposure of normal cells to radiation and so reduces the risk of damage to the body
Who needs to be protected every day from radiation?
What do they wear?
Where do they stand? (2)
How is the patient protected? (2)
Radiographers who work with x-rays and CT scanners
Lead aprons
Behind a lead screen or they leave the room
Lead is used to shield areas of their body not being scanned and the exposure time is kept to an absolute minimum.
What is used to produce ultrasound waves?
What are these converted into easily?
Electrical systems that can be made to produce electrical oscillations of any frequency
…mechanical vibrations to produce sound waves of a higher frequency than the upper limit of human hearing
What is ultrasound?
sound waves produced by mechanical vibrations, with a higher frequency than the upper limit of human hearing
….. waves get … reflected at a …. between …. .
Ultrasound, partially, boundary, media
What happens when a wave passes from one medium to another?
What is this called?
Some of the wave is reflected off the boundary between two media and some is transmitted
Partial reflection
What does partial reflection mean for the total amount of ultrasound waves being transmitted?
At a boundary between one substance and another some of the waves are reflected back
How is the distance from the wave emitter and the boundary tested for Ultrasound waves?
The time taken for the waves to reflect of the boundary and go back
