Basic guidewires consist of two central cores of straight wire around which is a tightly wound coiled wire spring (Fig. 9.1). The ends are sealed with solder. One of the central core wires is secured at both ends – a safety feature in case of fracturing. The other is anchored in solder at one end, but terminates 5 cm from the other end, leaving a soft flexible tip. Some guidewires have a movable central core so the tip can be flexible or stiff. Others have a J-shaped tip which is useful for negotiating vessels with irregular walls. The size of the J-curve is denoted by its radius in mm. Guidewires are polyethylene coated but may be coated with a thin film of Teflon to reduce friction. Teflon, however, also increases the thrombogenicity, which can be countered by using heparin-bonded Teflon. The most common sizes are 0.035 and 0.038 inch diameter. A more recent development is hydrophilic guidewires. These frequently have a metal mandrel as their core. They are very slippery with excellent torque and are useful in negotiating narrow tortuous vessels. They require constant lubrication with saline.

Figure 9.1 Guidewire construction. (a) Fixed core, straight. (b) Movable core, straight. (c) Fixed core, J-curve.

Catheters

Most catheters are manufactured commercially, complete with end hole, side holes, preformed curves and Luer lock connection. They are made of polyurethane or polyethylene. Details of the specific catheter types are given with the appropriate technique.

Some straight catheters may be shaped by immersion in hot sterile water until they become malleable, forming the desired shape and then fixing the shape by cooling in cold sterile water. For the average adult a 100-cm catheter with a 145-cm guidewire is suitable for reaching the aortic branches from a femoral puncture.

The introduction of a catheter over a guidewire is facilitated by dilation of the track with a dilator (short length of graded diameter tubing). If the patient has a large amount of subcutaneous fat in the puncture area, catheter control will be better if it is manipulated through an introducer sheath. This is also indicated where it is anticipated that frequent catheter exchanges may be required.

Taps and connectors

These should have a large internal diameter that will not increase resistance to flow. Luer locks stop the tap detaching during high-pressure injections.

FEMORAL ARTERY PUNCTURE

This is the most frequently used puncture site providing access to the left ventricle, aorta and its branches and has the lowest complication rate of the peripheral sites.

High Brachial Artery Puncture

Indications

As for femoral artery puncture, but as this approach is associated with a higher incidence of complications, it should only be used if femoral artery puncture is not possible.

Contraindications

1. Atherosclerosis of the axillary or subclavian arteries

2. Subclavian artery aneurysm.

Technique

1. The patient lies on the X-ray table with his arm in supination. The peripheral pulses are palpated and the brachial artery localized approximately 10 cm above the elbow.

2. A small incision is made in the skin, 1–2 cm distal to the selected point of arterial puncture.

3. A single-wall puncture needle is used, with an acute angle of entry into the artery.

4. A straight, soft-tipped guidewire is introduced when good pulsatile flow is obtained.

5. A 5-F pigtail catheter is introduced over the guidewire and its pigtail formed in the aorta.

6. At the end of the procedure the catheter tip is straightened using the guidewire and then removed. This reduces the risk of intimal damage and flap formation during withdrawal of the catheter.

AXILLARY ARTERY PUNCTURE

Indications

As for femoral artery puncture, but this approach is associated with a higher incidence of complications than femoral or high brachial artery puncture and should only be used if these techniques are not possible.

Contraindications

1. Atherosclerosis of the axillary or subclavian arteries

2. Subclavian artery aneurysm.

Technique

1. The patient lies supine on the X-ray table with his arm fully abducted. The puncture point is just distal to the axillary fold. It is infiltrated with local anaesthetic.

2. A small incision is made in the skin 1–2 cm distal to the point of the arterial puncture.

3. The needle is directed more horizontally than the femoral approach and along the line of the humerus.

4. Following satisfactory puncture the remainder of the technique is as for femoral artery catheterization.

GENERAL COMPLICATIONS OF CATHETER TECHNIQUES

Due to the anaesthetic

See Chapter 18.

Due to the contrast medium

See Chapter 2.

Due to the technique

Diagnostic angiography is an invasive procedure and complications are expected. The majority of these are minor, e.g. groin haematoma. Recommended upper limits for complication rates have been produced by the Society of Cardiovascular and Interventional Radiology (SCVIR):¹ these rates are included in the following discussion.

Local

The most frequent complications occur at the puncture site. Complication rate is lowest with a femoral puncture site:

1. Haemorrhage/haematoma – the commonest complication. Small haematomas occur in up to 20% of examinations and large haematomas in up to 4%. The SCVIR threshold for haematomas requiring transfusion, surgery or delayed discharge after diagnostic angiography is 0.5%. Haematoma formation is greater with larger catheters, more frequent catheter exchanges and heparin, antiplatelet or thrombolytic agents. Haematoma formation is also greater when the femoral artery is punctured high because of inadequate compression of the artery following catheter removal.

3. Infection at the puncture site.

4. Damage to local structures. Especially the brachial plexus during axillary artery puncture. Femoral nerve palsy can result from inadvertent infiltration of the nerve with local anaesthetic. It is short-lived but should prompt very cautious subsequent mobilization of the patient in case the leg ‘gives way’. More protracted femoral nerve damage can be due to excessive haematoma or pseudoaneurysm formation in the groin.

5. Pseudoaneurysm. The SCVIR threshold for diagnostic angiography is 0.2%. It presents as a pulsatile mass at the puncture site any time after arteriography and is due to communication between the lumen of the artery and a cavity within semi-solid or organized haematoma. Arterial puncture below the common femoral artery bifurcation increases the risk of this complication. Some may require surgical or interventional radiological repair.

6. Arteriovenous fistula – rare. SCVIR threshold is 0.1%. More common when puncture is below the common femoral artery bifurcation, because at this level the vein lies posterior to the artery and both are punctured in the standard double-wall technique.

Distant

1. Peripheral embolus – from stripped catheter thrombus. Emboli to small digital arteries will resolve spontaneously; emboli to large arteries may need aspiration thrombectomy through a catheter or surgical embolectomy. The SCVIR threshold is 0.5%.

2. Atheroembolism – more likely in older subjects. J-shaped guidewires are less likely to dislodge atheromatous plaques.

3. Air embolus. May be fatal in coronary or cerebral arteries. It is prevented by:

a ensuring that all taps and connectors are tight

b always sucking back when a new syringe is connected

c ensuring that all bubbles are excluded from the syringe before injecting

d keeping the syringe vertical, plunger up, when injecting.

4. Cotton fibre embolus. Occurs when syringes are filled from a bowl containing swabs or when a guidewire is wiped with a dry gauze pad. This very bad practice is prevented by:

a separate bowls of saline for flushing and wet swabs

OR, preferably,

b a closed system of perfusion.

5. Artery dissection – due to entry of the catheter, guidewire or contrast medium into the subintimal space. It is recognized by resistance to passage of the guidewire or catheter, poor back-bleeding from the catheter hub, increased resistance to injection of contrast medium or subintimal contrast medium on fluoroscopy. The risk of serious dissection is reduced by:

a not using a single-wall needle with a long bevel

b using floppy J-shaped guidewires

c using catheters with multiple side holes

d employing a small volume manual test injection prior to a pump injection

e careful and gentle manipulation of catheters.

6. Catheter knotting – more likely during the investigation of complex congenital heart disease. Non-surgical reduction of catheter knots is discussed by Thomas and Sievers.² Surgical removal after withdrawal of the knotted end to the groin may be the only solution in some cases.

7. Catheter impaction:

a in a coronary artery produces cardiac ischaemic pain

b in a mesenteric artery produces abdominal pain.

There should be rapid wash-out of contrast medium after a selective injection. A sound of sucking air on removing the guidewire and poor back-bleeding from the catheter indicate an impacted (wedged) catheter tip.

8. Guidewire breakage – more common in the past and tended to occur 5 cm from the tip, where a single central core terminates.

9. Bacteraemia – rarely of clinical significance.

References

1 Singh H., Cardella J.F., Cole P.E., et al. Quality improvement guidelines for diagnostic arteriography. J. Vasc. Interv. Radiol.. 2003;14:S283-S288.

2 Thomas H.A., Sievers R.E. Nonsurgical reduction of arterial catheter knots. Am. J. Roentgenol.. 1979;132:1018-1019.

Ascending Aortography

Echocardiography, multislice CT, and MRI are preferable initial imaging modalities for assessment of the ascending aorta.

Indications

1. Aortic aneurysm, trauma or dissection

2. Atheroma at the origin of the major vessels

3. Aortic regurgitation (echocardiography is more sensitive and less invasive if available)

4. Congenital heart disease – particularly the demonstration of congenital or iatrogenic aorto-pulmonary shunts and coarctation

5. As a preliminary to endovascular intervention, e.g. aneurysm repair.

Contrast medium

Low osmolar contrast material (LOCM) 370, 0.75 ml kg⁻¹ (max. 40 ml). Inject at 18–20 ml s⁻¹.

Technique

1. The catheter is introduced using the Seldinger technique via the femoral artery, and its tip sited 1–3 cm above the aortic valve.

2. The patient is positioned 45° RPO to open out the aortic arch, and to show the aortic valve and the left ventricle to best advantage.

3. A test injection is performed to ensure that:

a the catheter is correctly placed in relation to the aortic valve (which is particularly important in the hyperkinetic heart)

b the catheter tip is not in a coronary artery.

Films

20–30 frames s⁻¹.

Additional films

If, on the original run, the right common carotid artery overlies the right innominate artery or an aneurysm is present on the anterior aspect of the ascending aorta, the injection is repeated with the patient positioned left posterior oblique (LPO).

ARTERIOGRAPHY OF THE LOWER LIMB

Indications

1. Arterial ischaemia

2. Trauma

3. Arteriovenous malformation.

Contrast medium

All of these techniques can be performed under local anaesthesia with LOCM. 10–20 ml of 300 mg I ml⁻¹ concentration is suitable for the examination of one limb. 50 ml of 350 mg I ml⁻¹, at a rate of 12–15 ml s⁻¹, is suitable for a catheter aortogram.

BALLOON ANGIOPLASTY

Also known as percutaneous transluminal angioplasty or balloon dilation.

Indications

1. Dilation of localized vascular stenoses, mainly of the renal, iliac, lower limb and coronary arteries.

2. Recanalization of occluded segments of vessels in selected cases.Dilation procedures are often combined with preparatory diagnostic angiography in the same session; the majority are done under local anaesthetic. The procedure is often needed after lysis of arterial thrombus: this is outlined below.

Equipment

1. Digital fluoroscopy unit with C-arm capable of angiography and preferably with ‘road mapping’ facilities

2. Arterial pressure measuring equipment (optional)

3. Catheters:

a Gruntzig double-lumen balloon dilation catheters. Various manufacturers offer a wide range of balloon length and diameter combinations as well as catheter-shaft lengths, depending on the site and size of the vessel to be angioplastied

b Van Andel dilation catheter (a tapered, straight Teflon catheter, occasionally useful)

c straight Teflon or polyethylene catheters.

4. Guidewires:

a 0.035 or 0.038-inch diameter wires, typically 145 cm long; a slippery hydrophilic guidewire may be helpful for crossing tight stenoses

b 250 cm exchange guidewire.

5. Thrombolytic agents may be infused into recently thrombosed vessels, prior to angioplasty.

Technique

Principles

1. Adequate angiograms must be obtained before proceeding to angioplasty.

2. Angioplasty is always performed with the guidewire remaining across the stenosis or occlusion until the procedure is completed.

3. Adequate vascular surgical assistance must be readily available before attempting angioplasty.

4. If the history suggests that a thrombosis has occurred within the previous 3 weeks, thrombolysis may be helpful.

5. The patient should be anticoagulated during the procedure, using 3000–5000 units of heparin.

6. The balloon diameter is selected by reference to the measured size of the normal artery on the preceding angiogram, allowing for magnification.

Renal arteries

1. The tip of a suitable guidewire is negotiated through and beyond the stenosis in the renal artery, from either the femoral or high brachial artery approach.

2. A balloon catheter of appropriate diameter is positioned across the stenosis and distended (approx. 7 atmospheres for 1 min) after injecting 3000 units of heparin. A post-dilation angiogram is then taken. If a residual stenosis remains, further dilations or implantation of a metallic stent may be necessary.

Iliac arteries

1. These are preferably dilated from a retrograde femoral puncture on the side of the lesion.

2. If the femoral pulse is absent or difficult to feel, it may be located using US guidance or road mapping from a contralateral femoral approach. Alternatively a sidewinder catheter can be introduced from the opposite groin and a guidewire directed over the aortic bifurcation and across the lesion.

3. If possible, a femoral artery pressure should be measured immediately after introducing the catheter, and before a guidewire is passed through the lesion. This is to assess the severity of the pressure gradient before and after angioplasty.

4. A suitable guidewire is then advanced carefully through the stenosis. If the lesion is eccentrically situated, it may be preferable to advance using a pre-shaped catheter, to inject contrast medium to position the catheter, and then to advance through the patent lumen, avoiding possible intimal dissection from below. If the lesion is particularly tight, a hydrophilic wire may be useful.

5. A catheter is passed over the guidewire and into the distal aorta.

6. Some operators do not give heparin for straightforward iliac angioplasties.

7. The guidewire is removed, to allow a pressure measurement in the aorta. It is then replaced and the catheter exchanged for a balloon catheter. After dilating the lesion, an angiogram is performed and pressures checked to ensure that a significant gradient no longer exists. A wire or catheter remains across the stenosis until this is confirmed.

Femoral arteries (common, and origins of superficial femoral and profunda arteries)

1. These cannot easily be approached by an antegrade puncture on the side of the lesion since there is little room to manoeuvre and exchange catheters.

2. The contralateral femoral artery is catheterized using a sidewinder catheter. The tip is positioned in the iliac artery ipsilateral to the lesion and a guidewire advanced down through the lesion. The catheter is then exchanged for a balloon catheter and, after injecting heparin 3000 units, the lesion is dilated and a check angiogram performed before the guidewire is withdrawn. A long introducer sheath across the bifurcation facilitates smooth tracking of catheters and permits check arteriography throughout the procedure whilst still maintaining the wire across the lesion.

Superficial femoral and popliteal arteries

1. An antegrade puncture is performed (pointing in the direction of arterial flow) aiming to hit the femoral artery as it passes over the femoral head. The skin puncture site is correspondingly higher than a retrograde puncture. US is invaluable in antegrade punctures and most experienced operators use it wherever possible.

2. A 15-mm J-guidewire can be used to select the required branch; usually the superficial femoral artery.

3. The guidewire is advanced almost down to the lesion, and a straight Teflon or polyethylene catheter is inserted over the guidewire to the same point. The wire is then gently passed across the lesion with the catheter following. Digital road mapping guidance is helpful in many instances. A van Andel dilation catheter may be useful once the lesion has been traversed by the guidewire.

4. If gentle injection of contrast medium outlines a channel parallel to the expected lumen, dissection has occurred. The catheter should be withdrawn and attempts made to regain the lumen.

5. When the lesion has been passed the catheter is exchanged for a balloon catheter (usually 5 mm in diameter), 3000 units of heparin are injected and dilation is performed. The distal ‘run-off’ should be carefully assessed on the post-angioplasty films; success is related to the adequacy of ‘run-off’ and it is necessary to ensure that there has been no distal embolization of thrombus or atheroma.

Catheter-directed arterial thrombolysis

1. Chemical thrombolysis plays a role in the treatment of acute ischaemia of the leg due to:

a in-situ thrombosis of a stenosed vessel

b occluded lower-limb arterial bypass graft

c thrombosed popliteal aneurysm with no demonstrable distal run-off

d infra-inguinal embolus (sometimes iatrogenic post-angioplasty).

2. Thrombolysis should be undertaken in consultation with a vascular surgeon and should not compromise the leg unnecessarily by delaying surgical treatment. An acute episode less than 24-h old is more likely to respond to thrombolysis. After 14 days surgery is preferable to thrombolysis.¹

3. Irreversible limb ischaemia requires amputation to avoid reperfusion syndrome.

4. Absolute contraindications to thrombolysis include stroke within the preceding 2 months, a recent gastrointestinal bleed and neurosurgery or head trauma. Relative contraindications are major trauma or surgery, severe hypertension, brain tumour and recent eye surgery.

5. Recombinant tissue plasminogen activator (rt-PA) is the most widely used agent in the United Kingdom. It can be used as local boluses of, for example, 5 mg at 5–10-min intervals or as a low dose infusion at 0.5–2 mg hour⁻¹.

6. Catheter placement for thrombolysis is typically achieved by passing a guidewire alongside or through the thrombus and advancing a catheter into the proximal end. The catheter is firmly fixed to the skin to prevent dislodgement. A bolus of rt-PA followed by infusion is then administered through the catheter and the patient returned to a high-dependency ward for observation of signs of haemorrhage. Monitoring of clotting factors such as fibrinogen levels does not influence the likelihood of haemorrhagic complications.

7. Depending on the initial progress and discretion of the operator the patient returns after several hours for check angiography through the catheter. If necessary the catheter is advanced and infusion continued until satisfactory lysis, or the procedure is discontinued if progress is poor. Successful thrombolysis often reveals underlying stenoses as the cause of the occlusion. These are angioplastied at completion.

8. There are catheters manufactured for delivering fibrinolytics as a high pressure spray through multiple side holes over several centimeters of occluded vessel. These may be used manually or connected to a dedicated pump that measures and times the ‘pulse sprays’. This method has an added mechanical lytic effect and allows faster lysis. Other devices used in thrombolysis include hydrolyzing and mechanical thrombectomy catheters.

9. Bleeding complications are frequent, including haemorrhagic stroke in up to 2%.²

10. Thrombolysis is used widely wherever arterial and venous thrombosis occurs in the body. Many applications are not universally accepted and are off-license uses of the thrombolytic agent.

It is an important tool in the management of thrombosed haemodialysis access.

Aftercare

1. The pulses distal to the artery that has been dilated and the colour of the toes should be observed half-hourly for 4 h

2. Aspirin 150 mg daily (for life, unless there is a contraindication)

3. Reinforcement of the need to stop smoking.

Complications

Due to technique

1. Perforation of iliac artery leading to retroperitoneal haemorrhage

2. Embolization of clot or atheroma distally down either leg. This may be removed by suction thrombo-embolectomy or surgical embolectomy

3. Occlusion of main artery

4. Occlusion of collateral artery

5. Major groin haematoma formation, which may suddenly develop several hours after the procedure is completed

6. False aneurysm formation at the puncture site

7. Cholesterol embolization. Catheter manipulation disrupts atheroma and releases cholesterol crystals into the arterial circulation causing occlusion at arteriolar level. Pulses may be present and arteries patent angiographically but patients are restless and develop severe tissue ischaemia in the affected vascular territory with skin mottling, limb loss, stroke, bowel infarction and renal failure.

References

1 Ouriel K., Shortell C.K., DeWeese J.A., et al. A comparison of thrombolytic therapy with operative revascularization in the initial treatment of acute peripheral arterial ischemia. J. Vasc. Surg.. 1994;19:1021-1030.

2 Dawson K., Armon A., Braithwaite B.D., et al. Stroke during intra-arterial thrombolysis: a survey of experience in the UK (abstr). Br. J. Surg.. 1996;83:5-8.

Further reading

Working Party on Thrombolysis in the Management of Limb Ischemia. hrombolysis in the management of lower limb peripheral arterial occlusion a consensus document. J. Vasc. Interv. Radiol.. 2003;14(9 Pt 2):S337-S349.

Vascular Embolization

Indications

1. To control bleeding – from the gastrointestinal and genitourinary tracts, from the lungs and after trauma.

2. To infarct or reduce the blood supply to tumours or organs.

3. To reduce or stop blood flow through arteriovenous malformations, aneurysms, fistulae or varicoceles.

4. To reduce the blood flow in priapism.

5. As treatment for uterine fibroids.

Equipment

1. Digital fluoroscopy unit with C-arm capable of angiography and preferably with ‘road mapping’ facilities.

2. Pre-shaped femoro-visceral catheters. These should not have side holes since their presence promotes clumping of particles and fibres at the catheter tip leading to blockage of the lumen. Size and shape will depend on the particular problem. Balloon occlusion catheters and co-axial catheters may also be useful.

3. Embolic materials:

a Liquid – 50% dextrose, alcohol, quick-setting glues and polymers

b Particulate – gel-foam, polyvinyl alcohol, autologous clot

c Solid – Gianturco steel coils, detachable balloons.

The material used depends on the lesion, its site and the duration of the occlusion required. Use of materials other than those listed has been reported.

Patient preparation

1. As for arteriography

2. Some procedures are painful and sedo-analgaesia may be needed.

Aftercare

1. Observation of temperature pulse and blood pressure for signs of sepsis or bleeding

2. Observation of the tissues distal to the occluded vessel should be maintained for 24 h

3. Analgesia as required (patient controlled administration).

Complications

1. Misplacement of emboli: this may occur without the operator being aware that it has happened.

2. There may be propagation of thrombus, with embolization to the lungs or elsewhere.

3. Post-embolization syndrome results from infarcted tissue releasing toxins into the circulation. It comprises pain, fever, malaise, raised white cell count and inflammatory indices and transient impairment of renal function. Infarcted tissue can cause fever for up to 10 days. However, this tissue can become infected, and antibiotics may be required.

VASCULAR ULTRASOUND

US is a reliable, non-invasive, inexpensive test which is well tolerated by patients and widely used for assessment of the arterial system. Intra-abdominal or pelvic arteries are examined with US, but it is best suited to relatively superficial vessels such as those of the neck or lower limb. Chest arteries cannot be assessed by US because the sound will not adequately penetrate air or bone. The main disadvantages of US are the marked operator dependant nature of the technique and lengthy examination times for some studies.

The main components of arterial vascular US studies are:

1. Grey-scale US: gives anatomical information and detailed assessment of vessel wall including areas of intimal thickening or calcification

2. Pulsed-wave Doppler: measures changes in frequency of US waves reflected by moving blood within the vessel (Doppler shift). These data are used to calculate a detailed graph of direction and velocity of flow in the vessel. The normal pattern of flow differs between various arteries and flow patterns change at sites of disease such as narrowing (i.e. velocity of flow increases)

3. Colour Doppler: uses the same information as pulsed-wave Doppler but displays flow as colour superimposed in the arterial lumen on grey-scale imaging. Colour represents the direction and velocity of flow with red conventionally indicating flow towards the US transducer and blue representing flow away from the transducer. Rapid flow is displayed as white or yellow. This is helpful in selection of regions for detailed assessment with pulsed-wave Doppler or detection of A-V fistulae or pseudo-aneurysm

4. Power Doppler: a modification of colour Doppler which is more sensitive to slow flow or flow in small structures. However, it does not give information on direction or velocity of flow.

Further reading

Pellerito J.S. Current approach to peripheral arterial sonography. Radiol. Clin. North Am.. 2001;39(3):553-567.

Computed Tomographic Angiography

As CT technology has developed during the past few years, particularly with the introduction of 16 and 64 slice multidetector CT (MDCT) scanners, the quality and diagnostic usefulness of CT angiography (CTA) has improved dramatically.

CTA is performed as a block of very thin axial MDCT images obtained during the rapid peripheral intravenous (i.v.) infusion of iodinated contrast. The acquisition is timed to coincide with the peak density of contrast in arteries and the images subsequently re-constructed using post-processing techniques such as multi-planar reconstruction (MPR) or maximum intensity projections (MIP).

Although CTA involves administration of iodinated contrast (see Chapter 2) and significant radiation dose, there are many advantages: imaging is very rapid – usually less than 30 s to acquire the main dataset even for extended scans including lower limbs, scanners are readily available, unstable patients can be monitored with standard equipment, and valuable information is obtained about the blood vessel wall and surrounding structures.

PERIPHERAL (LOWER LIMB) COMPUTED TOMOGRAPHIC ANGIOGRAPHY

Description of other specific CTA methods are found in appropriate chapters.

Indications

1. Lower-limb ischaemia

2. Arterio-venous malformation

3. Trauma.

Patient preparation

General precautions for use of ionizing radiation (Chapter 1) and iodinated contrast (Chapter 2). The nature and purpose of the examination is explained to the patient.

Aftercare and complications

For iodinated contrast see Chapter 2.

Further reading

Chow L.C., Rubin G.D. CT angiography of the arterial system. Radiol. Clin. North Am.. 2002;40(4):729-749.

Duddalwar V.A. Multislice CT angiography: a practical guide to CT angiography in vascular imaging and intervention. Br. J. Radiol.. 2004;77(Spec no. 1):S27-S38.

Magnetic Resonance Angiography

Guidelines on MR safety and selection of patients must be followed (see Chapter 1).

MR angiography (MRA) is now in widespread clinical use and is a highly sensitive and specific tool for assessment of the arterial system. For most examinations contrast-enhanced MRA with i.v. gadolinium (see Chapter 2) is now the preferred method. Gadolinium i.v. shortens the T1 relaxation time of blood so blood appears bright when imaged with a very short TR (repetition time) and other structures on the image appear dark. Timing of the contrast injection is critical. Imaging without contrast is used infrequently, but may be either a ‘bright blood’ cine technique, to demonstrate both anatomical and functional data, or ‘black blood’ imaging, which gives useful morphological information.

The thoracic and abdominal aorta, carotid arterial system and major branches of the aorta including subclavian, celiac, superior mesenteric and renal arteries are routinely imaged with MRA. The pulmonary arteries are harder to image at MRA. Images are most often obtained as a block of thin coronal images (three-dimensional imaging) with contrast enhancement. Images are post-processed, including maximum intensity projection (MIP) series.

Previously, the arteries of the pelvis and peripheral arteries of the lower limb were difficult to image due to limited longitudinal field of view in MR scanners. More recent developments including elongated MR coils and ‘moving-table’ multi-station MRA have made high-quality examination of these vessels possible with a single injection of contrast and short imaging time. In some centres peripheral MRA is now routine and has replaced diagnostic catheter angiography.

Further reading

Earls J.P., Edelman R.R. Magnetic resonance angiography: body applications. In: Edelman R.R., Hesselink J.R., Zlatkin M.B., et al, editors. Clinical Magnetic Resonance Imaging. Philadelphia: Saunders-Elsevier, 2006.

Ho V.B., Corse W.R. MR angiography of the abdominal aorta and peripheral vessels. Radiol. Clin. North Am.. 2003;41(1):115-144.