4. CIRCLE OF WILLIS
• Grand Vascular Station of the Brain
• Classical –18% to 20%
• Majority circles shows anomaly-52%
• Most frequent anomaly is hypoplasia of ACA-24%
• Accesory vessels in the form of duplication/triplicationsof
ACOM (2 M.C.) -12%
Fetal posterior cerebral artery-10%
9. MIDDLE CEREBRALARTERY
• Larger terminal branch of ICA
• Run laterally in stem of lateral sulcus
• Curves on superolateral surface
• Runs backwards in depth of posterior ramus of lateral
sulcus
10. • M1 segment =horizontal segment from origin to its
bifurcation (it is in sylvian fissure)
• M2 segment =lacunar segment -in the insula loops over
insula—laterally to exit from sylvian fissure
• M3 segment = opercular branch-from sylvian fissure &
ramify over cerebral cortex
• Anomalies of MCA are uncommon
13. • 2 major terminal br of PCA—
•
• parieto occipital art & calcarine art
14. POSTERIOR FOSSA
• Vertebral artery
• Basilar artrery
• Vertebral arteries
• Originate from the subclavian arteries
• Left VA is dominant in 60% cases
16. BASILAR ARTERY
• Right and left VA unite to form basilar artery
• Courses infront of pons (Prepontine cistern)
terminates in the interpeduncular cistern
• 3cm in length,1.5 to 4mm in width
18. Normal VARIANTS
• Fenestrations and duplications
• Variants of the circle of Willis
• Persistent carotid-basilar anastomoses
• Anomalies identified in the skull base
23. Imaging Techniques
• Vascular structures of brain can be imaged by 4
means:
• 1. DSA: gold standard
• Invasive and risk of nephrotoxic contrast,ionising
radiation
• 2. Vascular ultrasound: least invasive, can be
done bedside, cost effective.
• Best choice for imaging vessels close to skin
surface.
24. • Drawback: limited anatomic coverage, deep
vessels cant be imaged, operator dependent,
requires skill.
25. • 3 CT angio: main drawbacks are contrast use and
radiation exposure,
• calcifications are overestimated.
• Preferred for aorta and coronaries
• 4 MRA : non invasive, no radiation exposure.
• Preferred for carotids and intracranial vessels as MRI
brain can also be obtained
• widely used in neurological disorders
26. • ANGIO?
• ‘ANGIO means blood vessel’
• SUBTRACTION?
• It is simply a technique by which bone
structures images are subtracted or canceled
out from a film of bones plus opacified vessels,
“leaving an unobscured image of the vessels”
27. DSA
• Acquisition of digital fluoroscopic images
combined with injection of contrast material
and real time subtraction of pre- and post
contrast images to perform angiography is
referred to as digital subtraction angiography
28. HISTORY
Portuguese neurologist Egas Moniz,( Nobel
Prize winner 1949), in 1927 developed the
technique of contrast x-ray cerebral angiography
to diagnose diseases,
such as tumors and arteriovenous
malformations.
29. • Idea of subtraction images was first proposed
by the Dutch radiologist Ziedses des Plantes in
the 1935, when he was able to produce
subtracted images using plain films.
30. HISTORICAL DEVELOPMENT
• CONVENTIONAL SUBTRACTION TECHNIQUE:
• Photographic method used to eliminate
unwanted images.
• No addition of information; only purpose to
make diagnostically important information
31. • Developed in 1970s, University of Wisconsin,
University of Arizona, University of Kiel.
• USA
• Commercial systems introduced in 1980.
32. • 3 conditions:
• SCOUT FILM
• ANGIOGRAM FILM-CONTRAST
• NO MOTION OF HEAD
33. PRINCIPAL
• Principles of subtraction are based on the
following:
• Scout film shows the structural details of the
skull and the adjacent soft tissue.
• Angiogram film shows exactly the same
anatomic details, if the patient does not move,
plus the opacified blood vessels.
34. • If all the information in the scout film could be
subtracted from the angiogram film, only the
opacified vessel pattern would remain visible.
37. WHY DSA?
• Digital subtraction angiography (DSA) was developed
to improve vessel contrast.
• Technique that uses a computer to subtract two
images, obtained before and after contrast media is
injected into the vessels of interest.
• Anatomical structures that are the same in the two
images can be removed and the resulting image
shows the vessels only
38. • Modern DSA systems are based on digital
fluoroscopy/fluorography systems, which are
equipped with special software and display
facilities
39. • Image before the contrast agent is
administered is called the mask image.
•
• Once the contrast is administered, a sequence
of images are taken by a television camera in
analog form, which is then digitised by
computer
40. • DSA processor has two separate image
memories, one for the mask and the other for
the images with contrast medium.
• These two image memories are subtracted
from one another arithmetically, and the result
goes to an image processing and display unit.
45. Contra indications
• No absolute contraindication.
• Poor renal reserve.
• Deranged coagulogram.
• Allergic to contrast media
46. Contrast Media
• Blood vessels are not normally seen in an x-ray
image, because of low tissue contrast.
• To increase image contrast, contrast agents,
which are dense fluids with elements of high
atomic numbers, such as iodine, are injected into
a blood vessel during angiography. Because of its
higher density and high atomic number, iodine
absorbs photons more than blood and tissue.
47. Creates detailed images of the blood vessels in
real time.
• First contrast media used for intravascular
injection were called high-osmolar contrast
media (HOCM).
48. • High osmolarity caused adverse effects such as
pain, endothelial damage, thrombosis, and
increased pressure in the pulmonary circulation.
• Low-osmolar contrast media (LOCM) were first
developed in the 1970's reduce side effects.
• Major risks of modern iodine contrast media is an
allergic reaction to iodine
49. • Non ionic Iso-osmolar contrast media.
• 30-40% dilution with normal saline.
• 50 ml of diluted contrast media is enough to do
a standard cerebral angiogram with total 8
projections.
• Approx. 5-8 ml diluted contrast / injection.
54. PREPARATION
• Nil orally 4-6 hrs.
• On trolley
• In hospital gown
• Groin shave
• Records
• Should be well
hydrated.
• Should void before
procedure.
• Peripheral pulses
marked.
• I.V line in place.
• Informed consent
55. PROCEDURE
• Gaining arterial access.
• Selective arterial catheterization.
• Image acquisition.
• Closure of arterial access.
• Post processing
• Hard copy
56. • Patients may be sedated to reduce anxiety.
• Monitor of vitals
• Local anesthetic is usually used in the area
where the catheter is to be inserted,
• Most common femoral artery
57. PROCEDURE
• Small incision given, medicut is inserted into the artery,
• Fluoroscopy is used to guide the needle to the proper
position .
• Needle is then removed after placing guide wire in the
artery and vascular sheath is inserted over the guide wire
.
• Catheter is then inserted along the guide wire through the
sheath
58. • When the catheter is in the correct position, the wire is
pulled out and dye is injected through the catheter.
• Images are acquired during contrast injection.
• Injections can be made directly into the artery of interest
(selective arteriography)
60. POSTPROCEDURAL CARE
• After the catheter is removed compression is applied to
the puncture site
• Bed rest for a minimum of 4 hours
• During rest patient is monitored and vital sign like
peripheral pulse like distal to Puncture are regularly
• Extremity is also checked for warmth, color, numbness to
ensure circulation has not been disrupted.
72. Digital subtraction angiography based
advances
• Better visualization and less radiation exposure
are key tenets in the development of digital
subtraction angiography
• Complexity of disease types increases and
more technically challenging, cutting-edge
procedures are performed
73. • Digital subtraction angiography systems with flat
panel : ADVANTAGES-
• High spatial resolution, wide dynamic range,
square field of view, and real-time imaging
capabilities with no geometric distortion—all of
which may be used for improve image quality,
reduced patient exposure to radiation
74. • Hatakeyama et al have shown that two-dimensional (2D)
and three-dimensional (3D)digital subtraction angiography
using the flat panel detector system of the direct
conversion type, with low radiation dose, is superior in
image quality for visualizing small intracranial vessels with
significantly decreased radiation exposure compared with
digital subtraction angiography with the conventional
image intensifier television system
• Hatakeyama Y, Kakeda S, Korogi Y, et al. Intracranial 2D and 3DDSA with flat panel detector of the
direct conversion type: initial experience. Eur Radiol 2006;16:2594 –2602.
77. • Allura Xper FD20/10 biplane flat detector
system with integrated 3D for intricate
neurovascular procedures.
• 3D- reconstructions
• Xper CT
• SPECTRA BEAM
• 3D Roadmapping
• multi-modality information integration
78.
79. • Redefines image clarity and captures
information at a resolution four times greater
than conventional X-ray systems.
80. Xper CT
• With XperCT clinicians can access CT-like imaging right
on the angio system so can assess soft tissue, bone
structure and other body structures before, during or after
an interventional procedure.
• XperCT reconstruction is created from rotational
acquisition performed on the Allura Xper system.
• This reconstruction can be overlaid with the 3D vascular
image.
81. • 3D soft tissue imaging supports diagnosis
planning, interventions and treatment follow-up
• XperCT can be combined with Allura 3D-RA
images to visualize soft tissue and vascular
anatomy on one image.
82. Spectra Beam
• Basically a selectable copper beam filtration
• Combination of Spectra Beam with the MRC-
tube allows increased X-ray output with better
filtration of soft radiation.
• Reduces patient X-ray dose for cardiac and
vascular applications, while maintaining the same
image quality.
83. Disadvantage of DSA
• Limited spatial resolution
• Artifacts
• Small visual field
• Not a good technique for neoplasm
84. Conclusion
• Despite recent advances in CT angiography and
MR angiography, DSA remains the standard
imaging technique for evaluation of the
cerebral vasculature .
• 3D reconstruction of the dataset acquired
during rotational DSA represents the latest
development in the neurovascular imaging .
85. • 3D-DSA has taken a prominent role in
treatment planning by enabling better
appreciation of the morphology of complex
vascular lesions before endovascular or surgical
management.
• Superior in the performance of sophisticated
tasks such as aneurysm volume measurement
86. • On the other hand, inability of 3D-DSA to
simultaneously image osseous and vascular
structures is noted as a weakness of this
technique compared with CT angiography .
87. Refrences-
• The Principle of Digital Subtraction Angiography and Radiological Protection;
K. OKAMOTO, . IT, K. SAKAI, S. YOSHIMURA ; Interventional
Neuroradiology 6 (Suppl1): 25-31, 2000
• Advances in Interventional Neuroimaging; Vallabh Janardhan and Adnan I.
Qureshi; Vol. 4, 414–419, July 2007 c The American Society for Experimental
NeuroTherapeutics,
• Intracranial Vascular Stenosis and Occlusive Disease: Evaluation with CT
Angiography, MR Angiography, and Digital Subtraction Angiography; Bash et
al; AJNR Am J Neuroradiol 26:1012–1021, May 2005
• Uptodate.com
• Digital substraction Angiography ;John hopkins Medical university
• Gray’s text book of anatomy
• Teachme anatomy .com
