Interventional Radiology Flashcards
What is interventional radiology?
What are the 2 most common imaging modalities that are used?
the use of medical imaging to undertake procedures and direct treatment
- ultrasound is commonly used to guide procedures (e.g. needle insertion for biopsies)
-
fluoroscopy is used to guide catheters through the circulatory system to target many different organs with minimal invasion
- e.g. coronary angiogram with stenting, EVAR, cerebral artery aneurysm coiling
- CT can be used, but MRI is not
- access to the patient is important and this cannot be acheived when they are in an MRI tunnel
What are the benefits of interventional radiology?
it is the least invasive procedure to achieve the best clinical outcome
- minimally invasive
- small incision reduces chance of infection
- local anaesthetic (not general)
- reduced hospital stay
What are the 2 categories of interventional radiology procedures?
they can be vascular or non-vascular
depending on whether things are being put inside blood vessels or outside of them
What are examples of vascular interventions?
-
angioplasty and stenting of coronary arteries / aorta
- this involves balloon dilation of vessels
-
aneurysm coil embolisation
- this involves pro-thrombotic coils being released into aneurysms
- embolisation of bleeding vessels
- IVC filters to reduce risk of massive PE
- thrombectomy to restore blood flow through an occluded vessel
- tunneled lines - for long term abx, chemo or TPN
- targeted delivery of drugs
What is the Seldinger technique and how is this performed?
- a compound needle (with inner cannula) is inserted into an artery
- the inner cannula is removed
- a guide wire is inserted through the needle and into the vessel
- the needle is removed
- a catheter is passed over the guide wire and into the vessel
- the guide wire is removed and the catheter remains within the area of interest
Why is coronary angiography performed?
How is this performed?
- it is performed to assess patency of coronary arteries, location and extent of occlusion (s)
- the femoral or brachial artery is punctured (via Seldinger technique)
- the brachial artery is often used as there is a reduced risk of pseudoaneurysms
- a catheter is passed to the coronary ostia under fluoroscopic guidance
- contrast agent is injected into the coronary arteries
- if there is an occlusion, a balloon can be inflated and stenting can be performed
- the balloon expands to compress the atheroma onto the sides of the vessel
What are the 2 different types of stent that can be used in coronary angiography?
What is the major risk associated with this procedure?
- stents can be open** or **covered
- any artery that a covered stent is placed across will become blocked off
- in the process of dilating the balloon and compressing the plaque, the plaque can fissure and expose the internal material that causes clots in the vessels
- the balloon can also be overdilated and rupture the vessel
What are the 2 different types of aneurysm?
What happens when they rupture?
- a fusiform aneurysm affects the whole artery
- a berry aneurysm comes off one side of the artery only
- when they rupture, the blood products cause vasospasm in nearby blood vessels and problems at the site of the aneurysm
How is cerebral artery aneurysm coil embolisation performed?
- catheter is inserted through the femoral artery and guided to the cerebral vessels under X-ray guidance (with contrast)
- when the aneurysm is located, more contrast is injected until the aneurysm is adequately visualised
- the catheter is hollow, so a second smaller catheter (microcatheter) is threaded through into the aneurysm
- coils are advanced through the microcatheter and into the aneurysm
- their position is checked and the coils are released
- this is only safe when the neck of the aneurysm is narrow, or else the coils may leave the site of the aneurysm
What happens in cerebral artery aneurysm coil embolisation if the neck of the aneurysm is wide?
- an uncovered stent may need to be placed to keep the coils in place
- this allows blood into the neck of the aneurysm, but won’t let the coils come out
- a flow-diversion stent can also be used - this is made of tight mesh that prevents blood flowing into the aneurysm
- do not want to do this when the aneurysm is near other small blood vessels in the brain as these could become unintentionally blocked
- a final check is made by injecting contrast to make sure that there is no flow into the aneurysm but normal flow in the vessel
What is shown in this image?
What is a problem with inserting coils and future imaging?
basilar tip aneurysm
- the aneurysm no longer fills with contrast after the coils have been inserted
- coils are made of metal so can result in a star dense metallic artefact on CT or a black hole on MRI
- this makes it difficult to visualise structures in close proximity to the coils
What are the indications for an IVC filter?
- DVT / PE when anticoagulation is an absolute contraindication
- DVT / PE despite adequate anticoagulation
- DVT / PE in pregnancy
How are IVC filters inserted?
When should they be removed?
- a jugular or femoral approach can be used
- an inferior venacavogram is performed first to look for clots and visualise the position of the renal veins
- the filter should be deployed below the level of the renal veins
- the clot will usually resorb once it is within the filter, or it may become calcified and remain within the filter
- they should be removed unless they are part of palliative care
What are the complications associated with IVC filters?
- bleeding
- haematoma
- filter tilting
- migration
- thrombus
What is EVAR?
How is it performed?
endovascular aortic repair
- most aortic aneurysms are fusiform and involve the whole lumen of the aorta
- a catheter is inserted via the groin and the lumen is excluded from the sac to prevent rupture
- preventing blood from entering the aneurysm stops it from increasing in size
- a covered stent is used to prevent blood getting into the aneurysm sac
- pre-procedural imaging is used to identify where the aneurysm starts and ends
- a healthy part of artery is needed either side of the aneurysm to hook the stent into
What are the possible complications of vascular procedures?
- vascular interventional radiology procedures can result in endovascular iatrogenic injuries that can be limb or life-threatening:
- pseudoaneurysm
- arteriovenous fistula
- groin haemorrhage
- retroperitoneal haemorrhage
- dissection
- there is also potential for wound infection / poor healing
Why might GI and biliary tree stenting be performed as part of palliative care?
- this opens the lumen, allowing the patient to eat and drink as normal to be comfortable
- stenting of the biliary tree in cholangiocarcinoma prevents severe jaundice
What is invovled in high intensity focussed ultrasound (HIFU)?
Why is this used and what is the benefit of this method?
- it is a completely non-invasive ablation technique
- as the US wave is propagated through tissue, some of the energy is absorbed as heat
- this uses a very small, focussed beam - this increases its intensity and the amount of heat energy absorbed
- it is used to ablate small, defined areas of tissue at the focal point whilst leaving surrounding tissue completely unharmed
What is HRFU usually combined with?
What is it usually used to treat and what are the disadvantages?
- it is combined with MRI to provide good anatomical localisation of tissue
- it is used to treat benign and cancerous tumours, particularly in areas that are difficult to operate on (e.g. pancreas)
- it can ablate regions that are millimeters in diameter
- disadvantage is that it has a long treatment time and the patient needs to lie completely still for over 2 hours
