Minimally Invasive techniques explained
In this section we explain how some of the common techniques we use in our procedures and address some common FAQs.
Are image guided procedures different from ‘keyhole’ surgery?
Image guided procedures performed by Interventional Radiologists are even less invasive than keyhole surgery.
How are image guided procedures different from keyhole or open surgery?
Keyhole or open surgery of the abdomen for example still requires for cuts to be made in the abdomen and even in the setting of keyhole surgery these can be several centimetres in size and several access ports are needed. In contrast image guided procedures usually use a single access point 4mm or less in size and frequently have significantly quicker recovery periods.
What is an angiogram or venogram?
An angiogram is an x-ray based procedure. It involves placing a plastic sheath into an artery or vein. Through this sheath further specialised plastic catheters may be directed to any desired artery and special dye may be injected to these vessels. This technique allows interventional radiologists to work out if arteries are narrowed or diseased or which blood vessels are contributing to bleeding or feeding unwanted growths or tumours. Based on angiogram findings further treatments may be performed using image guidance or in the case of diagnostic tests alternative treatments may be recommended.
What is embolization?
Embolization is a process in which special devices or materials are injected through an angiographic catheter to shut down a vessel or group of vessels. An angiogram is initially performed to identify region or vessel requiring embolization followed by the embolization itself which is performed under imaging guidance. Embolization material is released from the end of a catheter which is carefully positioned in the appropriate vessel prior to deployment.
There are in general four different types of materials used to this end. These include:
- Coils: These are essentially extremely flopping metallic wires which may be fed through the end of catheters. They are delivered through the end of catheters and curl up inside a vessel closing it from the inside. They produce an effect analogous to surgical ligation of blood vessels. Multiple coils may be placed in the same vessel allowing them to be used in both very large and extremely small vessels.
- Gelfoam: This is a biodegradable material that comes as a foam but is mixed with radiocontrast to form a slurry like suspension. It closes blood vessels from the inside and will travel down several branch vessels before settling. It is naturally resorbed by the body and this material is commonly used in surgery to prevent bleeding.
- Microparticles: Various formulations exist, however in essence these materials are small particles that will travel downstream from the vessel in which they have been injected before lodging in a smaller vessel. In general they produce a more profound reduction in blood flow than would be seen with coiling or surgical ligation. The flow directed nature of their deployment is often used to target tumours that like to draw in more than their fair share of blood for example.
- Liquid Embolic: There are a variety of agents which are liquid when injected to a catheter but solidify once exposed to blood. These range from expensive proprietary products with special viscosities to the humble cyanoacrylate or superglue (needless to say we only use specially manufactured, medical grade cyanoacrylate). These agents are extremely effective in the right hands, however they do require a skilled and experienced operator to achieve the optimal therapeutic result.
How do balloons work?
Balloons are inflatable devices which can be inflated in a blood vessel or other hollow tube in the body including bile ducts, ureters or bowel; most commonly they are used in blood vessels. Balloons are introduced into narrowed vessels in a deflated state and subsequently inflated to stretch open the narrowing. Most are designed to inflate to specified sizes and are often capable of sustaining extremely high pressures while holding their shape.
What are stents?
Most stents are essentially a special form of scaffolding which are used to hold tubular structures such as blood vessels and bile ducts open. Most stents are composed of metal ranging from stainless to steel to specialised alloys such as nitinol which are designed to hold their shape over time. Some stents may be lined with special material and this can be used, for example to seal off bleeding vessels form the inside. The majority of stents cannot be easily removed once they have been deployed.
What type of equipment do you use to get everything where you need it?
Most procedures begin with placing a plastic tube called a sheath into large vessel such as the femoral artery in the groin. This is achieved with a very small nick in the skin. The sheath has a waterproof valve through which the two main tools of the trade – wires and catheters can be inserted into the vessel and then guided to the area that need to be treated. Naturally we used specially designed wires with a variety of features including varying stiffness, lengths and even affinity for water which affects how ‘slippery’ they are. Being made of metal they are generally very easy to see under x-rays and often have gold or platinum coated tips to make them even more conspicuous.
Catheters are shaped plastic tubes which may be ‘railroaded’ over a wire so therefore once a vessel is selected with a wire a catheter can follow. A combination of catheters with shaped tips and wires are used to guide the Interventional Radiologist to the appropriate vessel.