transient ischaemic attack - imaging pathways

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The Imaging Pathway for TI A Iris C, Sarah C, Sharon D, Janine E, Sam F, Jessica K, Andrea K, Andrew N, George S, Phuong T Transien t Ischaemi c

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This is a group powerpoint presentation that I created for our university assignment - it explores the imaging pathways a worker in the medical imaging department would take with a patient suffering from a Transient Ischaemic Attack (TIA).

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Page 1: Transient Ischaemic Attack - Imaging Pathways

The Imaging Pathway

for

TIA

Iris C, Sarah C, Sharon D, Janine E, Sam F, Jessica K, Andrea K, Andrew N, George S, Phuong T

Transient Ischaemic Attacks

Page 2: Transient Ischaemic Attack - Imaging Pathways

What is a TIA?

A brief episode of neurological dysfunction caused by focal brain or retinal ischemia (loss of blood flow), with clinical symptoms lasting less than one hour, and without evidence of acute infarction. [Solenski, 2004]

StatisticsTransient ischemic attacks is an indicator for internal carotid arteries imaging, as there is a significantly increased risk of stroke [Jaff, et al., 2008]. It has been estimated that 4-20% of patients will have a stroke within the 90 days after the first TIA and 1/2 within the first 2 days. [Bonifati, et al., 2011]

Why is imaging important?TIA increases a patient’s risk of developing a stroke, therefore proper diagnosis and treatment is urgently required to reduce and prevent the risk of stroke recurrence, otherwise permanent brain injury, disability and even death may result.

Types of ImagingThere are a number of diagnostic imaging tests available: Cranial CT, CTA (CT angiography), MRA (MR angiography), DSA (digital subtraction angiography) and Doppler ultrasound.

Page 3: Transient Ischaemic Attack - Imaging Pathways

The Imaging Pathway

Page 4: Transient Ischaemic Attack - Imaging Pathways

Transient Ischaemic Attack (TIA)

Cranial CT

Carotid Doppler Ultrasound

Normal

30-70% stenosis +/- “non-surgical”

plaque

Endarterectomy

Angioplasty ± stent

Look for other sources of emboli

-Echocardiogram-Holter monitor

MRA

Tests congruent

Medical Treatment

> 70% stenosis on appropriate

side

MRA or CTA

Tests incongruent

Further non-invasive imaging

(do alternate test)MRA, CTA or DSA

< 70% stenosis> 70% stenosis

Tests congruent

Page 5: Transient Ischaemic Attack - Imaging Pathways

Transient Ischaemic Attack (TIA)

Cranial CT

What is Cranial CT and what role does it play in TIA imaging?

What is Cranial CT? Cross-sectional images of the brain in sagittal, axial and coronal planes via ionising radiation

Indications for Cranial CT: • Known bleeding tendency• Deteriorating level of consciousness• Unexplained progressive / fluctuating

symptoms• Papilloedema due to increased ICH • Neck stiffness• Fever or severe headache • Head injury (risk of subdural haematoma)

[Solenski, N.J., 2004 ]

What is its role in diagnosis?• The initial imaging modality of choice • Detects intracranial bleeding, such as

subdural haematoma, intra-cerebral haemorrhage or tumour mass

• Detects cerebral infarction appropriate to TIA symptoms in 15-30% of patients [Culebras, A., et.al 1997]

Technique: • Contrast is not initially used because

“there is a theoretical concern about promoting cerebral ‘toxicity’” [Culebras, A., 1997] – it may disrupt the blood-brain barrier in large infarcts

• If symptoms persist after 2 to 3 weeks, it is recommended to have contrast as the “fogging effect” may obscure the possibility of demonstrating infarction [Culebras, A., 1997]

Page 6: Transient Ischaemic Attack - Imaging Pathways

Do you agree with its position in the imaging pathway?Cranial CT should be the initial imaging modality in diagnosing TIA because of its: • Speed • Ability to exclude other brain

pathology, especially intracerebral haemorrhage as a cause of TIA

• Wide availability• Clinician familiarity with the

procedure [Smith, W.S., 2003]

Cranial CT excludes ICH (near 100% sensitivity) and subarachnoid haemorrhage (96% sensitivity) or subdural haematoma. [Culebras, A., 1997]

CT can also detect silent infarctions (contains no previous history) in 13% of cases and 47% of patients with TIA and known carotid stenosis. [Culebras, A., 1997]

Limitations of Cranial CT?• No abnormalities are detected on the CT

scan in early cases of infarction (1-4 hours), but cases of haemorrhagic infarction and massive MCA territory infarctions are more detectable [Culebras, A., 1997]

• Due to increase bony artefact in the posterior fossa, MRI is the preferred study over CT to evaluate disease in the brainstem or cerebellum [Tidy, C., 2010]

• Despite a normal appearance on a CT scan, an additional CT scan is required after 24 hours following the onset of stroke symptoms

• Pregnancy is a contraindication [Tidy, C., 2010]

Due to these limitations, other modalities such as Carotid Doppler Ultrasound are required to correctly diagnose TIA.

After five hours of acute onset of symptoms, cerebral infarction is indicated as a hypodense area

Page 7: Transient Ischaemic Attack - Imaging Pathways

Transient Ischaemic Attack (TIA)

Cranial CT

Carotid Doppler Ultrasound

Normal

30-70% stenosis +/- “non-surgical”

plaque

Endarterectomy

Angioplasty ± stent

Look for other sources of emboli

-Echocardiogram-Holter monitor

MRA

Tests congruent

Medical Treatment

> 70% stenosis on appropriate

side

MRA or CTA

Tests incongruent

Further non-invasive imaging

(do alternate test)MRA, CTA or DSA

< 70% stenosis> 70% stenosis

Tests congruent

Page 8: Transient Ischaemic Attack - Imaging Pathways

Transient Ischaemic Attack (TIA)

Cranial CT

Carotid Doppler UltrasoundWhat is Carotid Doppler and what

role does it play in TIA imaging?

What is Carotid Doppler?• Use of a high resolution linear array

transducer to view the carotid artery • B-mode scan, Colour flow Doppler, Spectral

Doppler velocities are employed when conducting the scan [Gaitini & Soudak 2005]

 What role does it play in TIA imaging? • 80% of ischemic events are caused by

atherosclerotic disease, commonly occurring at the carotid bifurcation [Landwehr P et al 2001]

• Stenoses can be identified and quantified quickly though Doppler which is used to measure blood flow velocity and turbulence and assists in the assessment of plaque morphology

• The degree of stenosis of the internal carotid artery is the primary parameter used for deciding upon therapeutic approaches for the patient. [Gaitini & Soudak 2005]

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Sensitivity and Specificity [Wardlaw et al 2006]{Wardlaw, 2006 #75}

  0-49% stenosis

50-69% stenosis

> 70-99% stenosis

Carotid Doppler Ultrasound

83% SE84% SP

36% SE91% SP

89% SE84% SP

Do you agree with its position in the imaging pathway?• Carotid Doppler Ultrasound assesses both morphology

and heamodynamic abnormalities quickly, easily, non-invasively and accurately

• Doppler assessments are necessary in determining therapeutic approaches, which are dependent on the degree of stenosis found [Gaitini & Soudak 2005].

• Carotid stenosis >70% is a high risk factor for stroke and 50% of subsequent strokes occur within 2 days

[Bonifati 2011]. Doppler allows physicians to determine the risk and monitor patients appropriately

• MRA is identified as the imaging modality for <70% stenosis as MRA is more sensitive in categorising moderate ranges of stenosis [Anderson, Glenn B et al. 2000].

Advantages DisadvantagesNon-invasive Heavy calcifications may

cause shadowing and occlude information

Cost effective Ultrasound probes cannot accurately examine carotid plaque under the mandible and the inter-cranial portion of the carotid artery (only useful for scanning along the patient’s neck)

Accurate Dependent on operator skill

Able to quickly diagnose

 

Helps to determine potential risk of stroke

Limitations of Carotid Doppler Ultrasound?• Doppler cannot always distinguish

between severe and complete occlusion due to undetectable blood velocity

• CTA AND MRA is indicated for patients with discrepant findings (e.g. with severe occlusion or atherosclerosis extending past the neck. ) [Gaitini & Soudak 2005]

Page 10: Transient Ischaemic Attack - Imaging Pathways

Transient Ischaemic Attack (TIA)

Cranial CT

Carotid Doppler Ultrasound

Normal

30-70% stenosis +/- “non-surgical”

plaque

Endarterectomy

Angioplasty ± stent

Look for other sources of emboli

-Echocardiogram-Holter monitor

MRA

Tests congruent

Medical Treatment

> 70% stenosis on appropriate

side

MRA or CTA

Tests incongruent

Further non-invasive imaging

(do alternate test)MRA, CTA or DSA

< 70% stenosis> 70% stenosis

Tests congruent

Page 11: Transient Ischaemic Attack - Imaging Pathways

Transient Ischaemic Attack (TIA)

Cranial CT

Carotid Doppler Ultrasound

Normal

Look for other sources of emboli

-Echocardiogram-Holter monitor

Page 12: Transient Ischaemic Attack - Imaging Pathways

Transient Ischaemic Attack (TIA)

Cranial CT

Carotid Doppler Ultrasound

30-70% stenosis +/- “non-surgical”

plaque

MRA

Medical Treatment

Tests congruent

Page 13: Transient Ischaemic Attack - Imaging Pathways

MRA

What is MRA and what role does it play in TIA imaging?

What is MRA?Magnetic Resonance Angiography (MRA) uses magnetic resonance techniques to evaluate extra- and intra-cranial vessels and any pathology such as stenosis and aneurysm.

MRA is the manipulation of data series of the Time-of-flight of moving protons and the spin phase of protons and the magnetic field gradients.

Technique:A magnetic field excites the protons in the brain’s tissue and the amount of signal released post-‘energy boost’ determines the different structures and tissues of the brain.

Why MRA?In the early stages of TIA, MRA is able to identify the area of arterial occlusion [Muir, K., & Santosh, C.,

2005].

The evidence of vessel occlusion by MRA has led to a “4-fold increased short-term risk of stroke” earlier detection of stroke. [Easton, J. et. al, 2009]

[Willinek, A. et. al, 2005]

Page 14: Transient Ischaemic Attack - Imaging Pathways

Statistics:MRA has a sensitivity of 92% and specificity of 76% in the detection of extracranial carotid disease [Easton, J. et. al, 2009].

MRA can identify carotid plaques, the inflammation in the vessel and the stability of the plaque [Easton, J. et. al, 2009].

Intracranial MRA is 90% sensitive and specific [Clifton, A., 2000].

“Overall, the non-enhanced MRA showed sensitivity of 84.2% and specificity of 84.6%. The enhanced MRA showed sensitivity of 69.2 and specificity of 73.6.” [Tomanenk, A. et. al, 2006]

 A 2005 study: MRA has a 100% sensitivity stenosis and occlusions > 70% were correctly identified. [Willinek, A. et. al, 2005].

[Townsend, T. et. al, 2003]

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Advantages Limitations- “…widely available

noninvasive technique that requires no radiation exposure and no administration of contrast material.” [Bash, S. et. al, 2005]

- Can be performed in conjunction with MRI

- If contrast is injected, it shortens time of flight

- “…requires comparatively long imaging times, frequently leading to patient motion artifacts and degradation of image quality.” [Bash, S. et. al, 2005]

- Patients with pacemakers or severe claustrophobia

- Non-enhanced MRA has a comparative lower spatial resolution than DSA and CTA [Bash, S. et. al, 2005]

- Contrast induced images often overestimates the severity of stenosis in vessels [Townsend, T. et. al, 2003]

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  > 30% stenosis

> 70% stenosis

> 70-99% stenosis

US 93% SE82% SP

93% SE92% SP

89% SE93% SP

MRA 89% SE82% SP

90% SE95% SP

86% SE93% SP

Is MRA justified in the flow chart?

Do you agree or disagree with the chart?:The position is justified.

MRA has a relative high sensitivity and specificity in regards to the detection of stenosis and occlusions as well as plaque, in the brain.

From the table results, it is clear that the sensitivity and specificity of stenosis > 30% is relatively high more sensitive modality for smaller stenoses.

Improvements?Need for more current research for more definitive results of TIA in MRA.  The imaging pathway does not account for the effect voxel size has on image quality.

“...decreased voxel size improves the delineation of cervical carotid and vertebral arteries in MR angiograms” [Willinek, A et. al, 2005].  

Need for alternative imaging?Patients with contraindications such as pacemakers, claustrophobia and patients whom are presented in the Emergency Room.

Page 17: Transient Ischaemic Attack - Imaging Pathways

Transient Ischaemic Attack (TIA)

Cranial CT

Carotid Doppler Ultrasound

Normal

30-70% stenosis +/- “non-surgical”

plaque

Endarterectomy

Angioplasty ± stent

Look for other sources of emboli

-Echocardiogram-Holter monitor

MRA

Tests congruent

Medical Treatment

> 70% stenosis on appropriate

side

MRA or CTA

Tests incongruent

Further non-invasive imaging

(do alternate test)MRA, CTA or DSA

< 70% stenosis> 70% stenosis

Tests congruent

Page 18: Transient Ischaemic Attack - Imaging Pathways

Transient Ischaemic Attack (TIA)

Cranial CT

Carotid Doppler Ultrasound

Endarterectomy

Angioplasty ± stent

> 70% stenosis on appropriate

side

MRA or CTA

Tests congruent

Page 19: Transient Ischaemic Attack - Imaging Pathways

MRA or CTA

Indications for CTA: Patients with suspected carotid artery disease such as occlusion, stenosis and aneurysms

Technique: Noncontrast CT of the head Contrast CTA from the aortic arch through the circle of WillisStatistics? For >70% stenosis Sensitivity of CTA is 0.77 and specificity is 0.95For patients with <70% stenosis Specificity is 0.67 and Specificity is 0.91

Why is CTA used? CTA is a quick, inexpensive and readily available way to assess stenosis in emergency patients after suspected TIA.

What is CTA and what role does it play in TIA imaging?

Page 20: Transient Ischaemic Attack - Imaging Pathways

Advantages DisadvantagesMore widely available than MRI

Risks associated with us of iodinated contrast

Less susceptible to artefacts as it uses digital subtraction techniques

Only accurate to assess >70% stenosis or occlusions.

Provides information about surrounding anatomy

Allows for radiation exposure of radiosensitive tissues (thyroid, lenses)

Faster scan time  

Is CTA justified in the flowchart?

Do you agree or disagree with its position in the chart? CTA should be used as a non-invasive imaging technique for patients with >70% stenosis as it is fast and offers accurate results. [Koelemay, Nederkoorn, Reitsma, & Majoie, 2004]

 Need for alternative imaging? CTA has a high sensitivity and specificity rate for patients with >70% stenosism However it is less accurate for 50-69% stenosis of the carotid artery.Therefore other tests, such as MRA or DSA should be preformed on these patients. [Wardlaw, Chappell, Best, Wartolowska, & Berry, 2006]

 Recommendations for further research: High sensitivity of CTA for >70% stenonis More research is needed on the accuracy of CTA in detecting stenosis <70%. [Wardlaw, et al., 2006]

Page 21: Transient Ischaemic Attack - Imaging Pathways

Transient Ischaemic Attack (TIA)

Cranial CT

Carotid Doppler Ultrasound

Normal

30-70% stenosis +/- “non-surgical”

plaque

Endarterectomy

Angioplasty ± stent

Look for other sources of emboli

-Echocardiogram-Holter monitor

MRA

Tests congruent

Medical Treatment

> 70% stenosis on appropriate

side

MRA or CTA

Tests incongruent

Further non-invasive imaging

(do alternate test)MRA, CTA or DSA

< 70% stenosis> 70% stenosis

Tests congruent

Page 22: Transient Ischaemic Attack - Imaging Pathways

Endarterectomy

Angioplasty ± stent

MRA

Medical Treatment

MRA or CTA

Tests incongruent

Further non-invasive imaging

(do alternate test)MRA, CTA or DSA

< 70% stenosis> 70% stenosis

Tests congruent

Tests congruent

Page 23: Transient Ischaemic Attack - Imaging Pathways

MRAMRA or

CTA

Tests incongruent

Further non-invasive imaging

(do alternate test)MRA, CTA or DSA

Page 24: Transient Ischaemic Attack - Imaging Pathways

Further non-invasive imaging

(do alternate test)MRA, CTA or DSA

What is DSA and what role does it play in TIA imaging?

Indications for DSA: vascular abnormalities such as occlusion, stenosis and aneurysms, “suspected carotid dissection unconfirmed on non-invasive neuroimaging study, subarachnoid haemorrhage, intracerebral haemorrhage in the absence of hypertension, and vasculitis.” [Solenski, 2004]

Technique: IV injection pre and post contrast digital imaging subtract precontrast images

Statistics: A study by Chilcote, et al (1981) revealed that DSA had a sensitivity of 95%, specificity of 99% and accuracy of 97%. DSA sens 46%, spec 74% for detecting plaque ulceration [Streifler, et al 1994]

Why is DSA considered gold standard? Superior spatial & contrast resolution (Jong et al,

2009), diagnosing severe (70-90%) stenosis [Herzig,

et al, 2004; Silvonnoinen, 2007], it is a dynamic study [Bash et. al, 2005]

Limitations of DSA? Very invasive procedure, 0.7% risk of peri-procedural neurological injury [Joshi and Prabhakaran, 2010], 1% risk of stroke, 4% risk of TIA, and nearly a 1% mortality rate.” [Silvonnoinen, 2007]

Figure 1. Still frames from an angiogram of carotid bifurcation in pt with ICA stenosis and stent placement

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Advantages of DSA

Advantages of Conventional Arteriography

• Decreased morbidity• Decreased patient

discomfort• Decreased hospitalisation

time• Decreased procedure time• Decreased film cost• Increased contrast

resolution• Usefulness in patients with

limited arterial access• Lower cost per examination

• Increased spatial resolution• Feasibility of selective

injections• Less degradation of patient

motion• Visualisation of small blood

vessels

Table: Comparative advantages of DSA and conventional arteriography. Retrieved from:

http://www.princeton.edu/~ota/disk2/1985/8506/850605.PDF

Page 26: Transient Ischaemic Attack - Imaging Pathways

CTA MRA DUS

Sensitivity 0.65 1.0 0.85

Specificity 1.0 0.57 0.71

Recommendations for further research: DSA assumed as gold standard (reference) no paper up-to-date that can evaluates the sensitivity and specificity of DSA alone.

US CTA CTA+US

Sensitivity 1.0 1.0 1.0

Specificity 0.75 0.844 0.844

Is DSA justified in the flowchart? Do you agree or disagree with the chart? The position is justified. Non- invasive imaging is the first line investigation for TIA.

Need for alternative imaging? Alternative non-invasive imaging methods are available and widely used. • DUS, CTA and MRA all show similar accuracy in

diagnosis of symptomatic carotid stenosis. No technique on its own is accurate enough to replace DSA.” [Patel, 2002]

• “A recent review of literature suggests that a carefully planned approach using non-invasive imaging can replace invasive angiography for carotid artery assessment in a cost-effective and safe manner” [Jaff, 2008]

Figure 1: Retrieved from Patel, 2002

Figure 2: Herzig, et al, 2004

Page 27: Transient Ischaemic Attack - Imaging Pathways

MRAMRA or

CTA

Tests incongruent

Further non-invasive imaging

(do alternate test)MRA, CTA or DSA

Page 28: Transient Ischaemic Attack - Imaging Pathways

MRAMRA or

CTA

Tests incongruent

Further non-invasive imaging

(do alternate test)MRA, CTA or DSA

< 70% stenosis> 70% stenosis

Page 29: Transient Ischaemic Attack - Imaging Pathways

Endarterectomy

Angioplasty ± stent

MRA

Medical Treatment

MRA or CTA

Tests incongruent

Further non-invasive imaging

(do alternate test)MRA, CTA or DSA

< 70% stenosis> 70% stenosis

Page 30: Transient Ischaemic Attack - Imaging Pathways

Endarterectomy

Angioplasty ± stent

Carotid Angioplasty +/- Stent (CAS) and Endarterectomy (CEA)CEA and CAS reduce and prevent embolic stroke recurrence/formation CEA CAS

What is it? Invasive surgical removal of plaque through an incision of blood vessel

Intra-arterial expansion using a balloon +/- stent

Indications - ICA stenosis > 70%, surgically accessible stenosis, patient is stable, stenosis is symptomatic, rates of surgical complication <6% [Findlay, et al., 1997]

- Suitable for high-risk patients who are not suitable for CEA

Contraindications

- Asymptomatic stenosis <60%, uncontrolled hypertension, diabetes, congestive heart failure, unstable angina or major neurological deficits [Findlay, et al., 1997]

- Diabetes mellitus- >80 y.o. [Hobson, et al., 2004]

- Ulceration of CA stenosis, >50% contralateral stenosis, echolucent plaque- Morphology increases risk of stroke in CAS, unfavourable anatomy [Maldonado, T., 2007]

What type of imaging is involved?

- Digital fluoroscopic imaging- Intraoperative Duplex US sens 100%, spec 100% [Wallaert, et al., 2011]- Angioscopy [Osman and Gibbons, 2001]- CT angiography sens and spec 90%- Transcranial Doppler Sonography + electroencephalography [Roh, et al, 2005]

- Digital fluoroscopic imaging- Intraoperative Duplex US, C arm post-stent angiography [Branchereau, A. and Jacobs, M., 2005]

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Conclusion

Imaging TIA to determine degree of stenosis medical/surgical intervention decrease stroke recurrence

Cranial CT is justified initial imaging modality due to its speed, availability, accessibility, and ability to identify and exclude brain pathology.

Stenosis > 70% : MRA + CT Angiography is justified. CTA preferred over MRA, more readily available, inexpensive and fast for emergency patients.

Carotid Doppler Ultrasound is quick, easy, relatively accurate, non-invasive and is able to identify degree of stenosis justified as a compliment to CT.

Stenosis 30-70%: MR Angiography is justified suitable for plaque identification.

Digital Subtraction Angiography (DSA)the "gold standard” BUT is fast being replaced by non-invasive imaging last resort imaging

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References

• Anderson, G., et al. (2000) CT angiography for the detection and characterization of carotid artery bifurcation disease. Stroke 31.9: 2168-2174

• Bash, S. Villablanca, J.P., Jahan, R., Duckwiler, G., Tillis, M., Kidwell, C., Saver, J., Sayre, J. (2005) Intracranial vascular stenosis and occlusive disease: evaluation with CT angiography, MR angiography, and digital subtraction angiography. American Journal of Radiology, 26(5), 1012-1021. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/15891154

• Bisschops, R., Kappelle, L.J. , Mali, W., Van der Grond, J. (2002) Hemodynamic and Metabolic Changes in Transient Ischemic Attack Patients : A Magnetic Resonance Angiography and 1H-Magnetic Resonance Spectroscopy Study Performed Within 3 Days of Onset of a Transient Ischemic Attack. Journal of the American Heart Association, 33:110-115. Retrieved from http://stroke.ahajournals.org/content/33/1/110

• Bonifati, D., Lorenzi, A., Ermani, M., Refatti, F., Gremes, E., Boninsegna, C., Filipponi, S., Orrico, D. (2011). Carotid stenosis as predictor of stroke after transient ischemic attacks. Journal of Neurological Sciences, 303, pp. 85-89. Doi: 10.1016/j.jns.2011.01.005

• Chilcote, W., Modic, M., Pavilcek, W., Little, J., Furlan, A., Duchesneau, P., Weinstein, M. (1981). Digital Subtraction Angiography of the Carotid Arteries: A Comparative Study in 100 Patients. Radiology, 139: 287-295. Retrieved from http://radiology.rsna.org/content/139/2/287.long

• Clifton, A. (2000). MR angiography. British Medical Bulletin, 56(2), 367-377.• Cloft, H., Joseph, G., Dion, J. (1999) Risk of Cerebral Angiography in Patients With Subarachnoid Hemorrhage, Cerebral

Aneurysm, and Arteriovenous Malformation : A Meta-Analysis. Journal of the American Heart Association, 30:317-320, Retrieved from http://stroke.ahajournals.org/content/30/2/317

• Culebras, A., Kase, C., Masdeu, J., Fox, A., Bryan, N., Grossman, C., Lee, D., Adams, H., Thies, W. (1997) Practice Guidlines for the Use of Imaging in Transient Ischemic Attacks and Acute Stroke. Ahajournals: Stroke; 28:1480 – 1497. Doi:10.1161/01.STR.28.7.1480

• Easton, J., Saver, J., Albers, G., Alberts, M., Chaturvedi, S., Feldmann, E., … Sacco, R. (2009). Definition and Evaluation of Transient Ischemic Attack: A Scientific Statement for Healthcare Professionals From the American Heart Association/American Stroke Association Stroke Council; Council on Cardiovascular Surgery and Anesthesia; Council on Cardiovascular Radiology and Intervention; Council on Cardiovascular Nursing; and the Interdisciplinary Council on Peripheral Vascular Disease: The American Academy of Neurology affirms the value of this statement as an educational tool for neurologists. Stroke, Journal of the American Heart Association, 40, 2276-2293. doi: 10.1161/STROKEAHA.108.192218

• Feldman, E., Cloft, H., Nguyen-Huynh, M., and McLaughlin, A. (2009). Vascular Imaging. In Jong, S., Louis, R., Caplan, K., Wong, K. (Ed.), Intracranial Atherosclerosis. Retrieved from http://books.google.com.au/books?id=cJ6hBWgF6X0C&pg=PA127&lpg=PA127&dq=why+is+dsa+gold+standard+for+TIA+imaging&source=bl&ots=-v_0r6WNvg&sig=Y--blDJSulzozXhPULgHL8IvUN4&hl=en&sa=X&ei=AV6IUeyrDIydiAf_l4DoAg&ved=0CC0Q6AEwAA#v=onepage&q=why%20is%20dsa%20gold%20standard%20for%20TIA%20imaging&f=false

• Findlay, J., Tucker, W., Ferguson, G., Holness, R., Wallace, M., Wong, H. (1997) Guidelines for the use of carotid Endarterectomy: current recommendations from the Canadian Neurosurgical Society, Can Med Asso. 157: 653-659. Retrieved from http://www.cmaj.ca/content/157/6/653.full.pdf

• Gaitini, D., Soudak, M. (2005) "Diagnosing Carotid Stenosis on Doppler imaging". The Journal of Ultrasound in Medicine. 24:1127–1136

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References

• Gaitini, D., Soudak, M. (2005) "Diagnosing Carotid Stenosis on Doppler imaging". The Journal of Ultrasound in Medicine. 24:1127–1136

• Grant, EG., Benson, C.B., Moneta, G.L., et al (2003). Carotid Artery Stenosis: Gray-scale and Doppler US diagnosis— Society of Radiologists in Ultrasound Consensus Conference. Radiology; 229:340– 346

• Herzig, R., Burval, S., Krupka, B., Vlachova, I., Urbanek, K., Mares, J. (2004) Comparison of ultrasonography, CT angiography and digital subtraction angiography in severe carotid stenosis. European Journal of Neurology, 11:774-781. Retrieved from http://www.upol.cz/fileadmin/user_upload/LF-kliniky/neurologie/Herzig_-_2004-6.pdf

• Hirai, T., Korogi, Y., Ono, K., Nagano, M., Maruoka, K., Uemura, S., & Takahashi, M. (2002). Prospective evaluation of suspected stenoocclusive disease of the intracranial artery: combined MR angiography and CT angiography compared with digital subtraction angiography. American Journal of Radiology, 23(1), 93-101. Retrieved from http://www.ajnr.org/content/23/1/93.long

• Hobson, R., Howard, V., Roubin, G., Brott, T., Ferguson, R., Pompa, J., Graham, D., Howard, G. (2004) Carotid artery stenting is associated with increased complications in octogenarians: 30 –day stroke and death r ates in the CREST lead-in phase., Journal of Vascular Surgery, Vol 40, No. 6, pp 1106-1111. Available from http://ac.els-cdn.com.ezproxy2.library.usyd.edu.au/S0741521404013059/1-s2.0-S0741521404013059-main.pdf?_tid=0978b716-b909-11e2-815d-00000aab0f6c&acdnat=1368146104_630dae0ea33715a932ccf403fb9b3d02

• Jaff, M., Goldmakher, G., Lev, M., Romero, J. (2008) Imaging of carotid arteries: the role of duplex ultrasonography, magnetic resonance arteriography, and computerised tomographic arteriography. Vascular Medicine, 13, 281-292. Retrieved from http://vmj.sagepub.com/content/13/4/281.full.pdf

• Josephson, S A., Bryant, S O., Mak, H K., Johnston, S C., Dillon, W P., Smith, W S.,(2004) Evaluation of carotid stenosis using CT angiography in the initial evaluation of stroke and TIA. Neurology, 63, 3 457-460. doi: 10.1212/WNL.0000135154.53953.2c

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