Introduction to Imaging

Question 1

What does the transducer in ultrasound produce and at what frequency?

Answer 1

Theres a transducer producing high frequency sound beams at a frequency of (2-20MHz)

Question 2

What does the computer analysis convert and into what in ultrasound scanning?

Answer 2

The computer analysis converts reflected sound waves into an electrical signal and grey-scale image

Question 3

What are the high frequency sound waves in ultrasound generated by?

Answer 3

generated by electric crystals within the ultrasound transducer (PIEZOELECTRIC)

Question 4

How does fat appear as in ultrasound and why?

Answer 4

Fat is high reflectivity of sound waves on ultrasound and appears white

Question 5

How does fluid appear in ultrasound?

Answer 5

Fluid(bile and blood) appears black on ultrasound

Question 6

How do we differentiate between fat and calcified prodcuts?

Answer 6

Sound waves are unable to penetrate calcium and so we get an acoustic shadow

Question 7

What is ultrasound scanning used in?

Answer 7

• Assessment of liver and biliary tract, solid organs
• Renal imaging: Kidney size, collecting systems, masses, calculi and cysts
• Occult abdominal collections, abscesses
• Obestric and gynaecological disease
• Vascular/doppler imaging
• Muscoskeletal

Question 8

What frequency of sound waves give better resolution and why?

Answer 8

Higher frequency sound waves give better resolution because the wavelength is smaller

Question 9

What frequency of sound wave penetrate deeper into the body?

Answer 9

Lower frequency sound waves penetrate deeper.

Question 10

Why is an ultrasound gel used?

Answer 10

Ultrasound gel is used to exclude air between the patient skin and probe

Question 11

What are plain films(X-rays) used in?

Answer 11

Used in X-rays for fractures

Question 12

What gram is being formed by plain films?

Answer 12

A shadow gram is being formed

Question 13

What color does bone appear in plain films?

Answer 13

Bones appear white

Question 14

What color does soft tissue appear in plain films

Answer 14

Soft tissue appear grey

Question 15

What is mammography used to look for and why?

Answer 15

Mammography is lesser x-rays looking for breast disease

Question 16

Why do bones appear white on plain films?

Answer 16

Ca2+ in bones stops x-rays from penetrating hence bones appear white on x-rays

Question 17

Why is contrast medium added in contrast studies?

Answer 17

Contrast medium is added to look at a particular structure in more detail

Question 18

What contrast medium is used for enteral structures?

Answer 18

Barium or iodine based(low osmolar non ionic) compounds for GI tract

Question 19

What contrast medium is used for intravenous structure and what is it used in?

Answer 19

Iodinated

Used for urography and venography

Question 20

What contrast medium is used for intra-arterial structure and what is it used in?

Answer 20

• Iodinated

- Used in peripheral vascular disease, coronary disease, renal transplants, cerebral circulation

Question 21

What contrast medium is used for ducts and tubes and what is it used in?

Answer 21

• Iodinated

- Used in salivary, naso-lacrimal, urethra, fallopian tubes

Question 22

What is computed tomography(CT) used in?

Answer 22

• Used in:
• Strokes
• Staging of malignant disease
• Trauma
• Pancreas and retroperitoneum
• Abdominal disease
• Chest mass and diffuse lung disease

Question 23

How does blood appear in a CT scan immediately and after a while when its an acute haemorrhage?

Answer 23

• Blood appears bright

- Blood turns grey after a while and eventually dark

Question 24

How does fluid appear in a CT scan?

Answer 24

Fluid will appear dark

Question 25

Contrast between fat and fluid on CT scan

Answer 25

Fluid will appear dark

Question 26

How does soft tissue appear in CT scans?

Answer 26

Soft tissue appears grey

Question 27

Contrast between air and fat in CT scan

Answer 27

Air is blacker than fat

Question 28

What does MRI use to form an image?

Answer 28

Uses a magnetic field to form an image

Question 29

How does a MRI scan work?

Answer 29

Radiofrequency pulse put through that excite hydrogen ions so that they rotate in a slightly different manner and release energy

Question 30

What are MRI scans used for?

Answer 30

• High resolution of brain
• Different cerebral disease
• Multiple sclerosis, HIV
• Spinal chord
• Orthopaedic
• Tumour staging
• Biliary tree
• Cardiac

Question 31

How does CSF appear in a T1 weighted MRI image?

Answer 31

CSF appears black

Question 32

How does fat appear in a T1 weighted MRI image?

Answer 32

Fat appears light grey/white

Question 33

How does soft tissue appear in a T1 weighted MRI image?

Answer 33

Soft tissue appears at various shades of grey

Question 34

How does CSF appear in T2 weighted image?

Answer 34

CSF appears white

Question 35

How does fat appear in T2 weighted image?

Answer 35

Fat appears dark

Question 36

What is the patient injected with in nuclear medicine?

Answer 36

Patient is injected with Technetium-99m

Question 37

What does the m in Technetium-99m stand for?

Answer 37

m means its metastable and decays and generates x-rays

Question 38

What is technetium attached to and depending on what?

Answer 38

Technetium is attached to certain compound depending on what structure we are scanning for

• Technetium is attached to another compound depending on the group of compounds we are looking at e.g if we are looking at bones it will be attached to MDP (an analogue of calcium phosphate). We are fooling the osteoblasts into thinking that the MDP is calcium phosphate as part of normal calcium homeostasis. The osteoblasts will take MDP from the bloodstream and stick it onto bone to form new bone. Osteoblasts lay down new bone
• Image this 4 hours later
• In areas with more bone turnover you will see more MDP deposited and more Technetium so you get more x-rays from that specific region

Question 39

What is nuclear medicine used in?

Answer 39

• Bone scanning for malignant disease, trauma
• Lung scanning
• Renal function
• White cell imaging
• Cardiac