Materials used for embolization
According to whether the resulting devascularization is permanent or temporary, the embolic agents can be classified as:
- Temporary agents: autologous blood clot, gelfoam powder and microfibrillar collagen
- Permanent agents:
- Particles: polyvinyl alcohol particles, trisacryl gelatin particles
- Coils (steel, tungsten or platinum) and balloons ( latex or silicone)
- Liquid includes sclerosants,adhesives and soluble plastics: ethanol, sodium tetradecyl sulphate,NBCA ( n butyl 2 cyanoacrylate),ethyl vinyl alcohol copolymer
HOW DOES PVA OR GELATIN PARTICLES WORK AS AN EMBOLIZATION AGENT?
- They cause an initial acute inflammatory response which is followed by a chronic foreign body reaction within weeks.
- Devascularization causes ischaemia and necrosis within hours which leads to swelling of tumours and may cause pain.
WHAT ARE THE VARIOUS SIZE OF PVA OR GELATIN MICROSPHERES?
- 40 to 800 microns in diameter
WHEN IS EMBOLIZATION BEST PERFORMED?
- Preoperative embolization is best performed the day before or immediately prior to operation.
WHAT ARE THE DISADVANTAGES OF SMALLER PARTICLES AND LARGE PARTICLES?
- Smaller particles will penetrate to smaller vessels, they are more likely to pass through arteriovenous shunts and reach the lungs. They also may cause ischaemic damage to normal tissues.
- Larger particles occlude proximal arteries and achieve less reliable tumour devascularization.
WHAT ARE THE DIFFERENT METHODS TO USE BALLOONS DURING EMBOLIZATION?
- Used for temporary test occlusion fixed to a catheter tip or
- Used for vessel occlusion by detaching and inflation using radiographic contrast media.
WHICH EMBOLIC AGENT IS CONSIDERED THE MOST PERMANENT FORM OF EMBOLIZATION?
- Liquid namely NBCA and copolymer ethylene vinyl alcohol.