Angiography

Angiography, also known as arteriogram or venogram, is a medical imaging technique producing an angiogram. It is based on contrasted x-rays used to visualise the lumen of blood vessels mainly focused on arteries and veins as well as organs of the body. The contrast agent is necessary as blood vessels are not clearly visible on normal x-rays. Angiography is mainly used to identify blockages or narrowing of blood vessels. The term angiography specifies the use of x-rays in this type of imaging. Computed tomography angiography is a variation of this technique that couples x-rays and computerized analysis of analysis whilst magnetic resonance angiography uses the same method as MRI to visualise the blood vessels of interest.

History
In 1927, a Portuguese physician, Egas Moniz first used the technique of contrasted x-rays to diagnose nervous diseases; tumours and artery diseases in the brain. The first angiographic procedures used sharp trocars to create a lumen for a catheter to pass through to the desired vessel or organ. This method resulted in high complications, mainly infection where the skin was cut and risk of haemorrhaging. In 1953, the Seldinger technique, named after a Swedish radiologist Dr Sven-Ivar Seldinger, greatly increased the safety of angiography. The desired vessel was located using ultrasound and is punctured using the trocar. The puncture site is much smaller than in the previous technique therefore decreasing the risk of excessive bleeding and infection. A round tipped guide wire is passed through the trocar and the trocar is removed. A sheath can be passed over the guide wire into the desired vessel followed by a catheter. This process is needed to inject the contrast agent into the vessel for visualisation.

Technique
Access to the blood vessel is mainly established through the femoral artery. This allows visualisation of the left side of the heart and the arterial system. The jugular or femoral vein is used to visualise the right side of the heart and the venous system. As previously mentioned, using the Seldinger technique, a guide wire and catheter is inserted into the desired vessel to insert the contrast agent. This contrast agent absorbs the x-ray and highlights the blood vessel when it moves through it and is easily identifiable as it appears white on the angiogram. As dense areas of the body like bones and certain organs, such as lungs, also absorb X-rays, they show up as white areas on X-ray images too. Using digital subtraction angiography, the bones and other organs are subtracted from the results so only vessels with contrast agent can be seen. As the contrast agent moves through the blood vessels, a series of X-rays can be taken to examine how it moves. By tracking its movement, radiologists can visualize and identify any problems with the blood vessels, such as blockages or sites where the vessel is narrower than usual.

'' Angiogram showing aortic arterial disease (narrowing of the arteries due to fatty plaques) at the point where the blood supply to the two legs separate. Arrow 1 shows the aorta and 2 shows the left common iliac artery ''

Cerebral angiography
Used to study the blood vessels in the head and neck if it is thought that vessels supplying the brain are narrowed or impeding blood flow which could result in a stroke. It can also be used after a stroke to assess the damage to the vessels or to identify an aneurysm or a brain tumour. By assessing the blood flow to the tumour, tumour growth can be analysed which can be useful in providing the best treatment.

Coronary angiography
Used to study blood vessels that supply the heart. Mainly used in patients who have had a heart attack, angina or heart disease which all involve blocked or interrupted blood vessels. This type of angiography can be used to determine which treatment would be most successful in patients with heart conditions ie if the patient had a narrowed artery but the damage was not severe, an angioplasty may be recommended but if the artery is clogged then an artery bypass graft may be more suitable.

Pulmonary angiography
Used to examine blood vessels in the lungs. It is frequently carried out on patients who have a pulmonary embolism. Computerised tomography pulmonary angiography using contrast agent then a CT scan is used in this case to lower the risk of complications.

Extremity angiography
Used to examine blood vessels in arms and legs. Mainly used if patient is suffering from extreme pain in the legs due to reduced blood flow to legs and feet. This type of angiography can also be used to identify atherosclerosis (plaque in the vessels) in the arms and legs.

Safety
The benefit of having an angiography greatly outweighs any risks that it may pose but nevertheless, no medical procedure is risk free. Minor complications that may occur include excessive bleeding or infection at the site of incision and an allergic reaction to the contrast agent used. There are more severe risks that could incur as a result of an angiography but these are very rare for example only 1 in 1000 people suffered a stroke due to this procedure. Other serious complications include blood vessel damage, organ damage and blood clots.