Medical Imaging

Question 1

What do x-rays do to living cells?

Answer 1

Ionise them - damaging them

Question 2

What are x-rays used for?

Answer 2

Medical diagnosis in hospitals

Question 3

What are x-rays ?

Answer 3

High frequency, short wavelength electromagnetic waves

Question 4

What is the same size as an x-ray wavelength?

Answer 4

The diameter of an atom

Question 5

What happens to the waves when they move through the body?

Answer 5

They pass through (transmitted by) healthy tissue but are absorbed by denser materials like bones and metal

Question 6

x-rays affect ……. …… in the same way as light so they can be used to take ….

Answer 6

photographic film, photographs

Question 7

What can x-ray photographs be used for? (+2 examples)

Answer 7

Diagnosing medical conditions such as bone fractures or dental problems

Question 8

How can x-ray images be produced electronically?

1. Using what?
2. What is that?
3. How does this thing create the image?
4. What is this technique also used for?

Answer 8

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

Question 9

What electromagnetic wave do CT scans use?

What do they produce?

Answer 9

x-rays

High resolution images of soft and hard tissue

Question 10

What does CT stand for?

Answer 10

Computerised axial tomography

Question 11

How does a person get CT scanned?

1. Where the person is…
2. Beamed…
3. Detected
4. Spin

Answer 11

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

Question 12

How is the CT scan image formed?

How do you get a 3D image?

Answer 12

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.

Question 13

What do x-rays cause that is useful to doctors?

Answer 13

They kills body cells if the dose is high enough so they can kill cancers, just like gamma radiation

Question 14

How do x-rays have to be controlled when killing cancers so that they don’t damage normal cells? (2)

Answer 14

They need to be: carefully focused, at the right dosage to kill not mutate or damage

Question 15

How are x-rays used to treat cancer in 3 points?

Answer 15

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

Question 16

Who needs to be protected every day from radiation?
What do they wear?
Where do they stand? (2)
How is the patient protected? (2)

Answer 16

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.

Question 17

What is used to produce ultrasound waves?

What are these converted into easily?

Answer 17

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

Question 18

What is ultrasound?

Answer 18

sound waves produced by mechanical vibrations, with a higher frequency than the upper limit of human hearing

Question 19

….. waves get … reflected at a …. between …. .

Answer 19

Ultrasound, partially, boundary, media

Question 20

What happens when a wave passes from one medium to another?

What is this called?

Answer 20

Some of the wave is reflected off the boundary between two media and some is transmitted
Partial reflection

Question 21

What does partial reflection mean for the total amount of ultrasound waves being transmitted?

Answer 21

At a boundary between one substance and another some of the waves are reflected back

Question 22

How is the distance from the wave emitter and the boundary tested for Ultrasound waves?

Answer 22

The time taken for the waves to reflect of the boundary and go back