Early Experience Comparing 16-slice CT Cerebral Angiography with 2D and 3D DSA in Cerebral Aneurysm Detection

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Early Experience Comparing 16-slice CT Cerebral
Angiography with 2D and 3D DSA in Cerebral
Aneurysm Detection

• Chandramohan S. MRCS, Keston P. FRCR FRCS, White
  P. MD FRCR
• Centre for Interventional Neuroradiology of
  Edinburgh (CINE)

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Purpose

• To compare 16-slice multi detector CT cerebral
  angiography (CTA) with conventional DSA and 3D
  rotational angiography (the reference standard).
• We review our experience and discuss the
  advantages and pitfalls of both modalities.

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Materials Methods

• 41 consecutive patients with acute subarachnoid
  haemorrhage (SAH) or symptomatic intracranial
  aneurysms.
• Initial evaluation was done by CTA.

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CTA Technique

• 16 slice multidetector CT (Sensation 16, Siemens,
  Erlangen).
• 0.75mm collimation, 15mm table feed /rotation.
• Images reconstructed at 1mm slice thickness,
  0.7mm interval.
• Contrast- 50mls Visipaque 270 (Iodixanol) _at_
  4mls/sec.
• 50ml saline flush _at_ 4mls/sec.
• Bolus tracking
• Monitoring images at base of CTA volume.
• Manual triggering as soon as contrast enters
  slice.
• Scanner has inbuilt 3 sec delay from this point.

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CTA Technique

• Volume obtained from C1 arch to level of corpus
  callosum.
• Restricted antero-posterior and transverse field
  of view (FOV) increases resolution of
  reconstructed images.
• Wide FOV images used if initial CTA was normal
  to exclude dural arterio-venous fistula.

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DSA Technique

• Catheter angiography performed in all cases
  (Axiom Artis, Siemens, Erlangen).
• Under GA at time of coiling in CTA positive cases
  (no aneurysms were clipped in this group).
• As a standard diagnostic procedure in the CTA
  negative cases.
• Initial 2D images.

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3D DSA technique

• Used to study all CTA positive vessels.
• Also all vessels where CTA was negative but high
  level of suspicion due to distribution of blood.
• Pump injection - 2 3 ml/sec during rotation (5
  sec).

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Interpretation of Images

• Images were reported independently by two
  neuroradiologists.
• Discrepancies were resolved by consensus.
• All images were reported using the manufacturers
  workstation (Wizard, Siemens, Erlangen).

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Interpretation of Images

• Several methods were used to evaluate the CTA
  dataset.
• Base Images
• Multiplanar reformatted views (MPR)
• 2mm slice thickness
• Maximum intensity projections (MIP)
• 5mm slice thickness
• Volume rendering technique (VRT)
• Preset protocol with surface enhancement,
  variable opacification levels and lighting
  effects.

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Interpretation of Images

• Angiographic images were reported from the
  workstation.
• 3D angiographic data was interpreted using VRT
  software and thick slab MIP images.

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Updated Results

• 41 patients (17 male, 24 female).
• Median age - 49 years (range 17 73)
• 35 patients had SAH on CT.
• CTA was positive in 32 patients (41 aneurysms).
• 44 aneurysms were identified in 32 patients on
  2D/3D DSA.

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Results

• The median maximal diameter of detected aneurysms
  was 6mm (range 1.5 12 mm).
• 3 aneurysms ( 2mm) were missed by CTA
• 2 of these were unruptured.
• Sensitivity of CTA was 93.
• Specificity was 100.
• All aneurysms were seen on CTA on retrospective
  review.

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Results

• One angiographic study could not be completed due
  to bilateral major vessel occlusions although CTA
  was diagnostic.
• CTA was well tolerated in all cases.
• No failure to obtain diagnostic images on CTA.
• No complications of CTA.
• Radiologist time per study is similar to DSA.

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Results

• Specific information in planning endovascular
  therapy could be obtained in almost all cases
  where the aneurysm was seen
• Site and size of aneurysm.
• Approach.
• Anatomical variants of the circle of Willis.
• Proximal vessel occlusions or stenosis (CCA
  bifurcation was included in several patients
  gt65yrs).

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Conclusion

• CTA is reliable in the diagnosis of all aneurysms
  gt2mm.
• Not a replacement for DSA
• Small aneurysms can cause SAH.
• Poor sensitivity for dural AV fistula.
• Catheter angiography is still necessary in
  perimesencephalic SAH or if the CTA is normal.

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Conclusion

• CTA has become our first line of imaging in all
  SAH patients
• Avoids catheter angiography prior to endovascular
  treatment.
• Well tolerated by ill patients.
• Facilitates planning of endovascular treatment.

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Conclusion

• Interpretation can be difficult
• Poorer spatial resolution in comparison to DSA
  (2D and 3D).
• Adjacent bone.
• Venous contrast contamination.
• Interactive use of 3D workstation is essential
• Base images
• MIP
• MPR
• VRT

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Examples
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Case 1

• 41y male with SAH.
• Correct CTA diagnosis of ACOM aneurysm.

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ACOM aneurysm is clearly defined
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Even the bleeding point is visible
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The CTA VRT and 3D DSA images also correspond
closely
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• When CTA is performed well the anatomical detail
  is very good.
• Close correlation with conventional angiography.
• The aneurysm dimensions also correlate well.

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Case 2

• 21y female with SAH.
• Multiple aneurysms seen on CTA.

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L Pericallosal
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L Pericallosal
L MCA
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L Pericallosal
Rt PICA
L MCA
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ACOM
L Pericallosal
Rt PICA
L MCA
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Lt ophthalmic aneurysm was missed on initial
review
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Lessons

• Multiple aneurysm occurs in 19 of the patients.
• Trace all intracranial vessels from the origin to
  the terminal branches.
• When your sure youve found them all go back
  and look again.

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Case 3

• 35yr Female.
• Right third nerve palsy.

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Poor bolus concentration leads to apparent vessel
narrowing or even non-visualisation on VRT
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The same vessels are normal on MIP images
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Also with catheter angiography
No PCOM aneurysm was found with ICA injections
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Lessons

• Careful injection technique is crucial to good
  results
• 20 gauge IV Cannula or larger.
• Proximal vein if possible.
• Ensure good connection and test with saline for
  adequate flow rate.
• Use bolus tracking to maximise arterial
  enhancement and minimise venous contamination.

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Case 4

• 57y female with SAH.
• Grade 1.

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3D DSA of R PCOM aneurysm
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Contrast from a previous run has pooled at the
fundus and falsely truncated the aneurysm
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CTA demonstrates the true morphology of the
aneurysm
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Lessons

• 2D and 3D DSA is susceptible to flow related
  artefacts, particularly in large or giant
  aneurysms.
• Enhancement during CTA is over a longer period,
  is more physiological and does not rely on
  subtraction imaging, rendering it more accurate
  in these cases.

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Case 5

• 36y female with SAH.
• Grade 2.
• CTA correctly diagnoses small Left PCOM aneurysm.

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L PCOM aneurysm (2.5mm)
Posterior Communicating Artery does not fill
during CTA
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L PCOM aneurysm (2.5mm)
3D DSA reveals patent PCOM vessel
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2D DSA confirms this finding
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The vessel is preserved following endovascular
occlusion of the aneurysm
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Lessons

• The physiological arterial filling during CTA is
  not always beneficial.
• Do not exclude a treatment option (e.g. Vessel
  occlusion) on the basis of absence of the PCOM,
  P1 or A1 segments on CTA.

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Case 6

• 60y male with SAH.
• CTA correctly diagnoses L M1 segment aneurysm.
• Is it suitable for coiling?

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Lt MCA aneurysm
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Apparent Sylvian fissure vein close to the Lt MCA
aneurysm
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• The aneurysm was thought suitable for
  endovascular occlusion.
• 3D DSA performed under GA prior to coiling.

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Proximal MCA branch from neck of 2mm aneurysm
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Proximal MCA branch from neck of 2mm aneurysm
Coiling was successful with preservation of
vessel and stable result at 6 months
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Lessons

• Venous contamination in CTA can make
  interpretation difficult, even with 16 slice
  imaging.
• There are management implications if CTA is used
  to select cases for endovascular treatment.

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Case 7

• 35y female with SAH.
• Predominantly perimesencephalic blood.
• Grade 1.
• Initially CTA reported as negative.

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Variable calibre of Basilar was thought to be due
to streak artefact in the posterior fossa
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Rotational Angio demonstrated mid-basilar
aneurysm arising from fenestration
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Retrospective review of CTA MIP reveals the
aneurysm
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Lessons

• Dont forget the uncommon aneurysm sites.
• Use MIP images in all planes to assess vessels
  close to the skull base.

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Case 8

• 44y female with SAH.
• Grade 1.
• CTA shows 2 aneurysms.

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Rt Cavernous ICA aneurysm
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Lt MCA aneurysm
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• Diffuse blood load.
• MCA most likely to have caused bleed.
• CTA suggested the ICA aneurysm lay below the
  dural reflection and would not require treatment.

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Coiled MCA aneurysm
DSA indicates cavernous aneurysm could lie close
to the dural reflection and cause SAH. This
aneurysm was also coiled.
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Lessons

• Actively search for cavernous carotid aneurysms
  they can cause SAH, particularly if medially
  pointing.
• Thin section MPR and base images are important to
  enable visualisation of these aneurysms which lie
  adjacent to bone.
• CTA may give a false impression of the
  relationship of these aneurysms to the dural
  reflection.

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Case 9

• Check you have got the Right side.

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Right
Right
Rt MCA aneurysm
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Lessons

• VRT images are often projected from above and
  behind to enable visualisation of the circle of
  Willis.
• DSA and cross sectional CT images are usually
  viewed in standard orientation.
• Potential source of reporting error.

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Case 10

• Grade I SAH.
• CTA correctly diagnosed a tiny (1.5mm) aneurysm.

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ACOM aneurysm
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Lessons

• Smallest aneurysm in which endovascular treatment
  by coiling is possible 1.8mm.
• Aneurysm of this size can be seen on CTA.
• Dont ignore apparently minor bulges at the
  common aneurysm sites.

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Thank You