L7: Imaging Anatomy

Question 1

What does imaging modalities refer to ?

Answer 1

Different techniques & technologies used in medical & biological science to capture images of the body

Question 2

Examples of imaging modalities

Answer 2

1) X-ray
2) Ultrasound
3) Computerised Tomography (CT, CAT scan)
4) MRI scan

Question 3

Define ‘invasive’ in medical terms

Answer 3

A medical procedure that ‘invades’ (enters) the body, usually by cutting/ puncturing the skin

Question 4

Give 1 example of minimally invasive and 1 example of invasive procedure

Answer 4

Minimally invasive: Injection
Invasive: Abdominal surgery

Question 5

Techniques in invasive imaging

Answer 5

• Contrast is introduced
• Injection of radioactive isotopes (PET)
• A probe is inserted

Barium contrast

Question 6

What are X-Rays a form of?

Answer 6

High-energy electromagnetic radiation

Question 7

Why was X-Ray called X in 1895?

Answer 7

At the time it represented ‘unknown’ radiation emitted by discharged tubes

Question 8

When was X-Ray discovered?

Answer 8

In 1895

Question 9

What did discharge tubes in X-ray developed into?

Answer 9

Development of vacuum tube that converts electrical input power into X-rays

Question 10

Explain what happens as X-Rays penetrate the body

Answer 10

Some of the energy is absorbed or scattered according to the different tissue densities

Question 11

Describe the relationship between density of the tissue and radiation

Answer 11

Denser the tissue, the more radiation is absorbed

Question 12

2 common uses of X-Ray technology

Answer 12

1) Chest X-Rays
2) Mammograms (breast screening)

Question 13

Advantages of clinical X-Rays

Answer 13

Cheap and quick
Painless & non-invasive

Question 14

Disadvantages of clinical X-Rays

Answer 14

Limited due to harmful radiation

Question 15

What does PA & AP X-Ray stand for?

Answer 15

PA: Chest Posterior Anterior
AP: Anterior Posterior

Question 16

Why is positioning of the film very important?

Answer 16

Proper assessment of organ dimensions

Question 17

What does AP X-Ray show?

Answer 17

Magnification of the heart & widening of the mediastinum

Question 18

Whats the most common use in mammograms?

Answer 18

Screen for tumours & main vessels around the heart during lateral chest X-Rays

Question 19

What does a contrast X-Ray show?

Answer 19

Show soft tissues more clearly

Question 20

How does contrast X-Ray work?

Answer 20

Radiopaque material (barium) is introduced into the body to coat the wall of the lumen

Question 21

What is the technique that combines the use of radiopaque material across time by studying moving body functions?

Answer 21

Fluoroscopy

Question 22

How does a computed tomography (CT) scan work?

Answer 22

Sending a narrow beam of X-Rays at the subject while the machine quickly rotates around the body, then the computer combines all these cross-sectional images to produce a 3D rendition

Question 23

Advantages of a CT scan

Answer 23

Basic structures, tumours more easily identified

Question 24

Disadvantages of a CT scan

Answer 24

More expensive, more training and takes longer to process

Question 25

What does PET stand for?

Answer 25

Positron Emission Tomography

Question 26

How does a PET scan work?

Answer 26

- Radioactive isotope attached to a drug (e.g injected), when the isotope collides with an electron in the tissue, it releases energy in the form of GAMMA RAYS - This is picked up by gamma cameras to produce a 3D image

Question 27

Why is a PET scan called a 'functional' imagine technique?

Answer 27

Uses a radioactive isotope

Question 28

Advantages of a PET scan

Answer 28

Able to detect changes with time

Question 29

Disadvantages of a PET scan

Answer 29

Minimally invasive (injection), costly, may need to combine with CT

Question 30

Why does cancer show up as bright spots in a PET scan?

Answer 30

Cells have a higher metabolic rate compared to normal, requires more sugar

Question 31

Why are CT & PET scans combined?

Answer 31

To explore the higher resolution of CT with the time-lapse of PET, to allow tumours to be precisely localised

Question 32

What does MRI stand for ?

Answer 32

Magnetic Resonance Imagery

Question 33

What is MRI based on ?

Answer 33

NMR (nuclear magnetic resonance)

Question 34

How does a MRI scan work?

Answer 34

- Most tissues contain water, which contains H+ atoms at the centre, which is the proton - These protons spin around an axis, this produces a magnetic field

Question 35

What needs to happen for an equilibrium to exist in MRI ?

Answer 35

No. of high energy electrons must be less than the low energy, the 'excess' protons are what produces the MRI signal

Question 36

What shows the image in MRI?

Answer 36

Pulse is emitted so all protons move in phase, when the pulse is stopped, the protons return to their original equilibrium and this produces a signal

Question 37

Name 2 equilibriums that take place in MRI

Answer 37

1) Out of phase (T2) 2) Lower energy state (T1)

Question 38

Advantages of MRI

Answer 38

Non-invasive, best resolution

Question 39

Disadvantages of MRI

Answer 39

Needs training, expensive

Question 40

Uses of a ultrasound

Answer 40

Monitor an unborn baby, diagnose condition, guide surgeon during certain procedures

Question 41

Advantages of ultrasound

Answer 41

Simple, portable, affordable

Question 42

How does a ultrasound work?

Answer 42

- Sound travels through tissues and sends echos which will differ in intensity/delay according to densities - Transducer will pick up the echoes & relay to a computer that converts each signals into a colour to build an image

Question 43

What does the colours in ultrasound scan mean?

Answer 43

Dark: Fluid & air Bright: Bony surfaces

Question 44

What do you see through a angiography scan?

Answer 44

Luminal structures (blood vessels/hollow organs)

Question 45

What does angiography need to access ?

Answer 45

Large vessel, minimally invasive

Question 46

How does a angiography work?

Answer 46

Contrast is injected which shows up as it absorbs X-Rays

Question 47

Define digital subtraction angiography

Answer 47

Subtracts bone & other organs so only vessels filled with contrast agent stays