12. Sentinal nodes Flashcards
Why is sentinal node imaging used?
To identify the sentinal node, in the lymph node chain to drain a tumour.
What does draining the interstitial fluid from a tumours sentinal node allow us to do?
To perform histology to assess metastasis.
What is done in the case the sentinal node has evidence of cancerous cells or not?
No cancerous cells - Assume nodes further up are clear.
Cancerous cell - Perform clearance of the area.
When is sentinal node imaging carried out?
Pre-surgery to aid localisation of the node.
Breast sentinal node localisation
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What is a sentinal node?
First node to receive lymphatic drainage from primary tumour.
Why is lymphatic drainage so significant?
It predicts auxillary status.
SN - is likely to be clear
SN+ may contain cancer ~ 50%
How are Tracers administered?
99mTc - prior to imaging
- DRL if same day surgery:20mBq
- DRL if following day surgery: 40 mBq
How is sentinal node imaging done?
- Tracer injected around tumour.
- Static aquisitions, imaging 15 mins after injection, 1hour after and 2-4 hours after injection.
Imaging is done with Co-57 flood source behind patient - done to improve outline of detection. - Patient imaged with arms to side.
How is sentinal node detection done in surgery ?
Combination of radioisotope and methylene blue
What are the key parts of a gamma probe?
- body and shielding
- collimator
- crystal, solid state/scintillation detector
- signal amplifier
Compare angled and straight gamma probes.
Angled probes - useful for searching in operating field. Large diameter - more sensitive, poorer spatial resolution.
Straight probes - Good for imaging deeper.
What is a hot node?
A sentinal node - first lymph node cancer spreads to - is not always cancerous.
What are the indications for carrying out lymphoscintigraphy imaging?
- Assessment of patient with lymphoedema
- primary abnormality - lack of lymph drainage
- secondary - lack of drainage caused by damage to lymphatic vessels.
What is lymphoscintigraphy?
Imaging to visualise lymphatic system - look for blockages + drainage.
How is lymphoscintigraphy performed?
- Tracer injected between web spaces in toes.
Image at a range of times post administration.
What does normal appearance of lymphoscintigraphy look like?
- Fast uptake into lymphatic tracts with visualisation of discrete lymphatic channels.
- Activity is usually in the inguinal nodes by around 1 hour, para-ortic by 2 hours and liver by 3 hours.
What does the appearance of lymphedema in lymphoscintigraphy look like?
Delayed and reduced transit of activity.
Poorly visualised + reduced number of lymph nodes.
Diversion of activity through the skin lymphatics indicated by dermal backflow ‘stocking sign’.
What problems may be encountered in lymphoscinitgraphy?
- Movement
- Discomfort
- Skin infection
