Lets see an example of one European country: UK. Stroke is the leading cause of death in UK after cancers and heart disease; 150,000 strokes and 20,000 transient ischaemic attacks (TIA or “mini strokes”) occur in the UK every year¹ costing the NHS over £2.8billion².

85% of strokes are caused by a blockage of the blood flowing to the brain; these are ischaemic strokes. The remainder are haemorrhagic strokes, in which a blood vessel in the brain bursts. In both types of stroke, brain damage can occur because the oxygen supply to part of the brain is restricted.

The new UK stroke strategy, launched on 5 December 2007³, urges to develop stroke services, which can image and treat high-risk patients with TIA within 24 hours.

Prompt diagnosis and treatment could potentially reverse the effects of stroke, thus reducing mortality and morbidity rates. The use of un-enhanced Computerised Tomography (CT) can confirm infarction and haemorrhage, which is a contra-indication to thrombolytic treatment. However, MR is shown to be 3 times more sensitive than CT during the initial 6-hour window⁴.

Because it is ubiquitous, accessible and fast, CT has been the mainstay of stroke imaging. However, there is a group of patients for which the CT scan is normal, and whose management may be changed by a prompt MR examination, when it is not contra-indicated. Few departments would be able to offer this access today, even for co-operative patients, because the usual scanning time of around 15 minutes added to patient preparation would cause considerable disruption to the MR schedule.

References:
1. Office of National Statistics Health Statistics Quarterly
2. National Stroke Strategy – UK Department of Health, Dec 2007
3. A 10 year objective of the UK government to deliver an urgent response to stroke patients linked to the Stroke and TIA Payments by Results documentation. It is predictable that UK MR units will be given new service delivery targets.
4. Chalela JA et al. 2007 "Magnetic resonance imaging and computed tomography in emergency assessment of patients with suspected acute stroke: a prospective comparison" Lancet; 369: 293-98

• Top of the page

GE Healthcare partnered with key clinical sites to develop a protocol tailored for all Signa HD platforms, including axial T2-weighted imaging, coronal FLAIR imaging and diffusion-weighted imaging (DWI).

The objective of this protocol is to accommodate such urgent TIA examinations within a department's existing schedule.

The detachable patient trolley is a key clinical tool, which enables preparation of the patient outside of the MR room, and helps to save time to the MR examination.

Any rapid access MR scanning referral is via consultant, with full co-ordination from the stroke team. The patient has an initial CT scan; if this is deemed undiagnostic an MR may be requested. The MR list is minimally disrupted and results are ready immediately after the scanning procedure.

The following two cases demonstrate the use of this protocol.

• Top of the page

72 year old female patient with renal failure.

A		B		C
A. CT scan ~ 6 hours showing right occipital infarct with possible chronic left parietal infarct.
B. CT scan 2 weeks post event patient symptoms deteriorated.
C. Axial T2 weighted scan showing right occipital infarct with sub-acute haemorrhage.

D		E
D-E. Coronal FLAIR images showing multiple ‘watershed’ infarctions.

F		G		H
F-G. DWI showing several ‘watershed’ infarctions. Acute right sided middle cerebral artery territory stroke, confirmed by ADC images (H-I).

I		J
J. Note gradient echo B0 DWI useful to detect haemorrhage!

Fast MR Stroke protocol

• Axial T2 (36 sec.) TR 3000 ms / TE 85 ms ETL 21 30 slices of thickness 4 mm / gap 0.5 mm
• Coronal FLAIR (2:00 min) TR 7500 ms / TE 107 ms 32 slices of thickness 4 mm / gap 1 mm
• Axial DWI (40 sec.) TR 10000 ms / TE Minimum 22 slices of thickness 5 mm / gap 1 mm

• Top of the page

68 year old patient with dysphasia and right-sided symptoms.

A		B		C
A. CT scan ~ 5-6 hours post infarction – reported as normal
B-C. Axial T2 and Coronal FLAIR images showing left middle cerebral artery territory oedema

D		E
D-E. DWI and apparent diffusion coefficient confirming acute left sided stroke.

Fast MR Stroke protocol

• Axial T2 (36 sec.) TR 3000 ms / TE 85 ms ETL 21 30 slices of thickness 4 mm / gap 0.5 mm
• Coronal FLAIR (2:00 min) TR 7500 ms / TE 107 ms 32 slices of thickness 4 mm / gap 1 mm
• Axial DWI (40 sec.) TR 10000 ms / TE Minimum 22 slices of thickness 5 mm / gap 1 mm

• Top of the page

This protocol, made possible by the Signa™ HD 1.5T platform, adapts the existing head protocols to minimise acquisition time whilst maintaining a highly diagnostic scan. The detachable patient trolley also plays a role in reducing the patient preparation time.

Rapid access to MR scanning in acute stroke patients can complement initial CT scanning thus streamlining patient care pathways. This technique is both practical and achievable and causes minimal disruption to MR scanning lists.

• Top of the page