Digital subtraction angiography (DSA) is a technique used to visualize blood vessels by subtracting bone and tissue structures from angiograms, leaving only images of opacified blood vessels. It involves acquiring digital fluoroscopic images before and after injecting iodinated contrast media and subtracting the pre-contrast images from the post-contrast images in real-time. DSA allows for both diagnostic evaluation of vascular anatomy and interventional procedures such as aneurysm coiling or tumor embolization. While generally safe, DSA does carry risks of local vascular complications, systemic reactions to contrast media, or neurological deficits in rare cases.
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ANGIO?
ANGIO means blood vessel
And angiography is the radiological study of blood
vessel in the body after the
introduction of iodinated contrast media.
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.
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DSA-The 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
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The Portuguese neurologist Egas Moniz,( Nobel Prize winner 1949), in
1927developed the technique of contrast x-ray cerebral angiography to
diagnose diseases, such as tumors and arteriovenous malformations.
The 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.
With the introduction of the Seldinger technique in 1953, the
procedure became safer as no sharp devices need to remain inside the
vascular lumen.
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HISTORICAL DEVELOPMENT
CONVENTIONAL SUBTRACTION TECHNIQUE
Photographic method used to eliminate unwanted
images.
No addition of information;only purpose to make
diagnostically important information to see.
First described by a Dutch radiologist, Zeides des
Plantes, 1935.
3 conditions:
SCOUT FILM
ANGIOGRAM FILM-CONTRAST
NO MOTION OF HEAD
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The principles of subtraction are based on the
following:
The 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.
If all the information in the scout film could be
subtracted from the angiogram film, only the
opacified vessel pattern would remain visible.
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Contra indications
No absolute contraindication.
• Poor renal reserve.
• Deranged coagulogram.
• Allergic to contrast media.
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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.
This creates detailed images of the blood vessels in real time.
The first contrast media used for intravascular injection were called high-osmolar
contrast media (HOCM). (osmolality is the measure of the particle concentration in
a solution.)
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HOCM had osmolarity seven to eight times higher than
plasma. This 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 and these helped to reduce these side effects.
One of the major risks of modern iodine contrast media is an
allergic reaction to iodine.
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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.
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PREPARATION
Appointment time
Nil orally 4-6 hrs.
On trolley
In hospital gown
Groin shave
Records
PTI
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Should be well hydrated.
Should void before
procedure.
Peripheral pulses marked.
I.V line in place.
INFORMED CONSENT
MUST
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PROCEDURE
Gaining arterial access.
Selective arterial catheterization.
Image acquisition.
Closure of arterial access.
Post processing
Hard copy
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During angiography, patients may be sedated
to reduce anxiety.
Their heart rate and rhythm, breathing, and
oxygen saturation are monitored throughout
the procedure.
Patient clean draped .
A local anesthetic is usually used in the area
where the catheter is to be inserted, most
commonly the femoral artery.
First, a small incision given, medicut is inserted
into the artery. fluoroscopy is used to guide the
needle to the proper position .
The needle is then removed after placing guide
wire in the artery and vascular sheath is
inserted over the guide wire . The catheter is
then inserted along the guide wire through the
sheath.
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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)
Complications from an arteriogram are very
rare, but there is some risk. Most problems that
occur can be detected at the time of the procedure
or immediately after the procedure. The artery may
be injured at the puncture site or along the artery
where the catheter is passed.
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POSTPROCEDURAL CARE
After the catheter is removed compression is
applied to the puncture site.
The patient is asked for 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
The extremity is also checked for
warmth, color, numbness to ensure circulation
has not been disrupted.
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Oral fluid is given and analgesics are given if
required.
Special care should be given in case of children and
geriatric patient since additional Patience is
required. They have given warming blanket to keep
the body temp. Normal.
Geriatric patient also frequently feel nervous and
afraid of falling off the Table ,reassurance
and additional care from the technologist will
enable the Patient to feel secure and comfortable.
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Therapeutic usage
• Onyx embolization
Onyx HD500 is comprised of 20% EVOH
(ethylene vinyl alcohol) copolymer dissolved in
DMSO (dimethyl sulfoxide), and suspended
micronized tantalum powder to provide
contrast for visualization under fluoroscopy.
Onyx HD500 (20% EVOH) is an HDE device
for the treatment of
intracranial, saccular, sidewall aneurysms that
present with a wide neck (≥ 4mm) or with a
dome-to-neck ratio < 2 that are not amenable
to treatment with surgical clipping.
Onyx HD500 can also be used in adjunctive
therapy with Axium coils and stents.
