Medical applications of physics

Question 1

Describe 5 properties of x-rays.

Answer 1

1. They are transverse waves.
2. They form part of the electromagnetic spectrum.
3. They have very short wavelengths of the same order of magnitude as the diameter of atoms; 1 nanometer.
4. They can cause ionisation
5. They affect photographic film in the same was as light.

Question 2

Where can x-rays be used?

Answer 2

In hospitals to diagnose and treat some medical conditions, e.g. bone fractures, dental problems, CT scans.

Question 3

How can x-rays be detected?

Answer 3

Using CCDs to form an image electronically.

Question 4

What are two advantages of using x-rays for medical applications?

Answer 4

1. They are transmitted healthy tissue.

2. They are absorbed by metal and bone to produce shadow pictures.

Question 5

What are 2 advantages of using CT scans over x-rays?

Answer 5

1. Significantly more detail is obtained in CT images as CT scans can distinguish between different soft tissues.
2. A 3D image can be obtained in a CT scan.

Question 6

What are 2 disadvantages of using CT scans over x-rays?

Answer 6

1. A patient will be exposed to a higher dose of radiation in a CT scan.
2. CT scans are more expensive.

Question 7

What can be used to monitor and limit exposure to x-rays?

Answer 7

1. Adequate protective screeing.
2. Protective clothing.
3. Personal radiation detectors.

Question 8

What are ultrasound?

Answer 8

Sound waves of frequencies greater than 20,000. They are non-ionising.

Question 9

What is the hearing range for humans?

Answer 9

20 Hz - 20,000 Hz.

Question 10

What can be used to generate ultrasonic waves?

Answer 10

Electronic systems, which produce electrical oscillations.

Question 11

What happens to ultrasonic waves as they pass from one medium or substance into another?

Answer 11

They are partially reflected at the boundary.

Question 12

What equation can be used to determine the distance between boundaries or interfaces?

Answer 12

s = v x t
s is the distance in metres, m.
v is the speed in metres per second, m/s.
t is half the time taken for the pulse to leave the source, reflect off the boundary and return to the detector in seconds, s.

Question 13

What are three uses of ultrasound in medicine?

Answer 13

1. Pre-natal scanning.
2. Imaging of damaged ligaments and muscles.
3. Imaging of kidneys and destruction of kidney stones.

Question 14

Why can’t x-rays be used for baby scans?

Answer 14

Because they are ionising and therefore they will harm the baby/mother.

Question 15

Name two ways in which x-rays can be detected.

Answer 15

1. Photographic film.

2. CCD.

Question 16

Give four examples of ultrasound used in medicine.

Answer 16

1. Pre-natal scanning.
2. Imaging damaged ligaments and muscles.
3. Imaging kidneys.
4. Removal of kidney stones.