Imaging of circulatory diseases Flashcards
Anatomical vs functional imaging
Anatomical shows structure, functional shows movement/flow etc.
Eg Anatomical: Plain radiographs catheter angiography Ultrasound Ct/mri
Functional:
Radionuclide imaging
Mri functional imaging
ultrasound
What does a doppler scan do?
Tells you about flow through vessle and which directio in relation to the scanner (towards or away)
What is a MRA?
A contrast MRI (MR Angiography)
What is catherter angiography?
VESSEL PUNCTURED AND CATHETERISED.
STERILE PROCEDURE
CONTRAST INJECTED USING PUMP INJECTOR
RAPID SERIES OF IMAGE ACQUISITION
What can we tell from a lung scintigraphy?
Ventilation/perfussion ratio, it is a type of nuclear imaging.
What do you ask when looking at a scan?
Remember ABLF Anatomy Blockages Leaks Flxable?
What colour is thrombus on ct?
Grey, like other body matter, flow of blood (white) will stop.
How much per min of leak to see?
2-3 ml per mins to see it on a scan. Also have to remember that if a small leak can stop leaking for scan and then start agai after- it is only a snapshot.
Is it easy to differentiate acute and chronic thrombosis blockages on CT scans?
No
Urinary tract and arterial cacifications would be looked at with or without contrast CT ?
Without contrast- the calcifications come up white and with contrast would merge into the same as the blood in the vessles.
When is the Arterial/venous/nephrogenic/delayed phases of contrast CT
Arterial phase is within first minute (15-40s)
Venous - 70-80s
Nephrogenic = 100s
Delayed phase - shows fibrous tissue as doesn’t leave as easily, 6-10 minutes post injection.
Ideal properties of man mdae contrast agents
HAS AN ATTENUATION COMPARABLE TO SURROUNDING SOFT TISSUES.
INEXPENSIVE
INERT
EQUAL DISTRIBUTION IN AND OUT OF SELECTED BODY COMPARTMENTS
PAINLESS
EASE OF USE
Most common tcontrast used? isks with this contrast
Iodinated contrast:
Kidneys! (renal disfunction)
MAJOR ALLERGIC REACTIONS RENAL DYSFUNCTION DISTURBANCE OF THRYOID METABOLISM DISTURBANCE OF CLOTTING MECHANISM SEIZURES PULMONARY OEDEMA
What ato consider before using contrast?
ANY PREVIOUS CONTRAST ALLERGIES.
ASTHMA/ATOPY (both make more likely to have a reaction to the contrast agent)
POOR RENAL FUNCTION - will make worse
METFORMIN - a drug used on diabetes - clashes with iodinated agents, causes renal failure and lactic acidosis, withhold dose after contrast agent for 1-2 days
Contrast reactions commonly are what and what is the treatment?
Dose-related / chemo-toxic Nausea Itching Flushing (Seizures, arrhythmias) Management is usually supportive, if mild
Can be allergic reactions (Anaphylaxis / anaphylactoid (IgE / non-IgE mediated):
- Hypotension
- Pulmonary oedema
- Bronchospasm
- Convulsions
, treated with antihistamines or salbutamol if less severe otherwise as per anaphylaxis guidelines
What is the piezoelectric crystal? What is B mode?
It is the part of an ultrasound that is the transmitter and receiver, transmits the ultrasound waves and receives them and translates (turns back into electricity so they can be converted into a picture.
B mode is Brightness/2D mode, scans an anatomical plane, anatomical representation of structures.
M mode?
Motion mode, less commonly used, asses heart valve movement and heart chamber dimensions and functions.
What is Doppler used to show?
The direction and velocity of blood flow.
Red =? Blue =? Doppler uses mainly?
Red is away, blue is towards. Used a lot foe dtection of DVT.
What is Ultrasound contrast used for?
Characterising lesions (dynamic uptake pattern)
Assessment of organ perfusion (eg. Liver cirrhosis)
Delineating organ edge (eg. For irregularity of heart valves)
Alternative to CT/MRI if unable to tolerate/allergic to other forms of contrast.
Shows a much clearer image.
What are the pros of spiral ct? (360 CT)
Speedy, can do patient in one breath (less motion artefact and able to get through more patients) . Potentially lower radiation dose. Better coordination with IV contrast (more specific to the time you want to capture). Also can get multiplanar image reconstruction.
What does Houndsfield unit represent?
Represents the density of a specific material on a CT.
air = -1000, water is 0, bone is +1000.
HU is proportional to water/air x 1000
Hounsfield 0 = ? 1000? -1000?
0=water
1000 = bone
-1000=air
What is windowing? eg sort tissue window?
it is capturing within set ranges of hounsfield units (eg +200 to -200) to help amplify the contrast in soft tissue structures (fat = -60 to -120, soft tissue is +20 to +70)
