Imaging in circulatory disease

Question 1

What are the anatomical vascular imaging ?

Answer 1

Plain radiographs
Catheter angiogram
Ultrasound
CT/ MRI

Question 2

What are the functional vascular imaging ?

Answer 2

Radionuclide imaging
MRI functional imaging
Ultrasound

Question 3

What is a catheter angiogram ?

Answer 3

Vessel punctured and catheterised
Sterile procedure
Contrast injected using pump injector
Rapid series of image acquisition

Question 4

What are the challenges with vascular imaging ?

Answer 4

We cant see important structures very well:
	 - blood vessels
	 - lumen of hollow viscera 
Functional significance of lesion
Is treatment effective

Question 5

What are the limitations of CT ?

Answer 5

Leaks:
- Wont identify small volume leaks
- Cannot exclude intermittent bleeding
Blockages:
- Cant differenciate between acute and chronic inflammation
Anatomy:
- Can be difficult to convey complex anatomy to non-radiologists

Question 6

What is the ideal properties of contrast agents ?

Answer 6

Has an attenuation comparable to surroudning soft tissues
Inexpensive
Inert
Equal distribution in and out of selected body compartments
Painless
Ease of use

Question 7

How are vessels visualised ?

Answer 7

Intravenous contrast:

- High density (iodine)
- Inert
- Painless
- Cheap
    - X-ray attenuation

Question 8

What are the problems with iodinated contrast ?

Answer 8

Major allergic reactions
Renal dysfunction
Disturbance of thyroid metabolism 
Disturbance of clotting mechanisms
Seizures
Pulmonary oedema

Question 9

What are important considerations before using contrast ?

Answer 9

Any previous contrast allergies
Asthma/atopy
Poor renal function
Metformin:
      - Rare complication in which contrast cause renal failure

Question 10

What are contrast reactions ?

Answer 10

Dose related/ chemo toxic:
	- Nausea 
	- Itching
	- Flushing
	- Seizures/arrhythmias 
Anaphylaxis:
	- Hypotension
	- Pulmonary oedema
	- Bronchospasm
        - Convulsions

Question 11

How does ultrasound work ?

Answer 11

Electricity-> ultrasound waves-> reflects back, off boundaries in tissues-> turned back into electricity-> converted into pictorial form

Question 12

What is B-mode ?

Answer 12

Scans an anatomical plane
Gives anatomical representation of structures
Used in almost all types of ultrasound scans

Question 13

What is M-mode ?

Answer 13

Less commonly used
Fixed plane over time
To assess heart valve movement as well as chamber dimensions and function

Question 14

What is doppler ?

Answer 14

Flow alters frequency of ultrasound waves returning to probe
To show direction/ velocity of flow
Common clinical use include detection of DVT

Question 15

What are ultrasound contrast ?

Answer 15

Contrast made from microbubbles

Inert gas, surrounded by a shell

Question 16

What are the indications for ultrasound contrast ?

Answer 16

Characterising lesions
Assessment of organ perfusion
Delineating organ edge
Alternative to CT/MRI if unable to tolerate/ allergic to other forms of contarst

Question 17

What are the principles of CT ?

Answer 17

Spiral CT:
- Enables acquisition in dingle breath hold
- less motion artefact
- better coordination with IV contarst
- Much quicker -> higher pateint reconstruction
Back projection:
- Uses attenuation of radiation in multiple planes

Question 18

What is windowing ?

Answer 18

Changes shading of pixels to make easier to appreciate structures
Windowing level refers to CT unit assigns as the midpoint of the scale
Window range refers to the range of values around this