Imaging

Question 1

Strengths of x-rays

Answer 1

• Good at showing things surrounded by air
• Good at showing things surrounded by bone
• Good at showing things that destroy white bone (e.g. cancer)

Question 2

Weaknesses of x-rays

Answer 2

along side with the danger of radtion
its very diffculte to distingusih tissues with similar density

Question 3

How do x-rays produce an image?

Answer 3

1. Electric current heats cathode
2. Electrons are emitted + strike anode
3. X-rays exit window, penetrate patient and scatter
4. X-ray film is blackened when the X-ray hits the film.

Question 4

X-ray studies are more dangerous than computerized tomography in terms of ionising radiation. True/False

Answer 4

False CT scans usually require more exposure to radiation than common x-rays because they use a series of x-ray images.

Question 5

How does a CT scan produce an image?

Answer 5

Combines a series of X-ray images taken from different angles around the patient and uses computer processing to create cross-sectional images

Question 6

Q5. Which of the following is not true for an MRI.
A. MRI is the most suitable assessment for the brain

B. MRI is a great technique to measure acute tendon and muscle tears.

C. MRI is poor at showing details of the lungs

D. MRI has no contraindications

Answer 6

D

Question 7

How does an MRI produce an image?

Answer 7

1. Scanner creates strong magnetic field
2. Scanner produces a burst of radio signal which energizes the body’s protons
3. Scanner listens for return signal produced by protons and uses signal to produce image

Question 8

Computerized Axial Tomography (CAT) scan is essentially:
A. X-ray of soft tissues

B. A finer X-ray of bones

C. A detailed x-ray

D. X-ray of brain

Answer 8

C

Question 9

The cooling agent for the MRI magnet is

Answer 9

Helium

Question 10

If an MRI was done for a long bone, the part of the bone that will be imaged is the
A. Bone salts

B. Bony Prominence

C. Inflamed Joints

D. Bone Marrow

Answer 10

D

Question 11

Strengths of MRI

-

Answer 11

No ionizing radiation
- Can assess acute muscle and tendon tears, especially in deep tissues
- Interior of joints can be imaged e.g BONE MARROW
- Most complete assessment of the brain

Question 12

Weaknesses of MRI

Answer 12

• Expensive
• Can be harmful
• Some patients may find the process claustrophobic
• Scans take a long time

Question 13

How is an ultrasound image produced?

Answer 13

1. Piezoelectric crystals convert electrical energy into acoustic energy; crystals are housed in a transducer which has an electrical supply
2. US machine transmits sound pulses into patient
3. Some sound waves get reflected, some travel further until they reach another boundary and get reflected
4. Machine calculates the distance from the probe to structure, and forms a 2D image on the screen

Question 14

Strengths of US

-

Answer 14

No ionizing radiation
- High spatial resolution – can show organs, muscles and tendons

Question 15

Weaknesses of US

Answer 15

• Bone and gas block US
• Difficult to perform on fat patients