4. DSA - principles, indications, contraindications
DES =
= drug-eluting stent - stent is placed into a narrowed vessel and slowly releases a rug to block cell proliferation (prevent fibrosis -> restenosis)
Contraindications:
Allergy to contrast medium Renal dysfunction Deranged coagulogram.
Principles:
Based on the principle of fluoroscopy • Real-time subtraction of pre- and post- contrast injection images o Water-soluble iodine-containing contrast medium (CO2) o Blood vessels are not normally seen in an x-ray image due to low contrast. o Iodine absorbs photons more than blood and tissue. • Improves the perception of vessels with removal of background anatomy (bones)
(DSA) Digital subtraction angiography
Classical invasive method to clearly visualize blood vessels in a bony or dense ST environment. • It is the basis of all interventional procedures o Therapeutic = diseases/conditions are treated through endovascular acesss. o Diagnostic investigations are being replaced by sectional imaging .e.g CT or MRI angiography.
Complications
Complications: rare Hematoma (subcutaneous) Retroperitoneal hemorrhage Thromboembolism, dissection of vessel wall, infection
Types of substractions
Mask mode substraction Time-interval difference subtraction Dual energy subtraction Hybrid substraction K-edge substraction
Procedure:
Seldinger technique Local anesthesia • Puncture of common femoral artery (ipsilatera, contralateral), just below the inguinal ligament with sharp hollow needle o Alternatives: axillary, brachial, radial, popliteal a. o Transradial: more used by cardiologists - less risk of bleeding, but higher risk of occlusion. o Venous system: femoral or popliteal veins o Transfermoal: best approach - the diameter of the puncture site is quite big (7mm), it is closed to the head of femur (after procedure we can compress the puncture site to stop the bleeding). o Currently we have different devices to occlude puncture site after procedure, so risk of bleeding is now very low. • Guidewire is advanced through the lumen of the needle and the needle is withdrawn. • Sheath is passed over the guidewire into the vessel and the guidewire is removed. • Sheath can be used to introduce catheter or other devices to perform endoluminal procedures. o Pigtail catheter: typically used for an overview angiography. o Sidewinder: selective or super-selective depiction of vessel. • Add iodine contrast
Indications:
Therapeutic: embolization, coiling, stenting, thrombolysis, thrombectomy • Usually combined with endovascular treatment: Diagnostic: thrombosis, aneurysm, arterial dissection, non-traumatic SAH, AVM, AVF, tumour vascularity • Rarely for diagnostic purpose anymore, CTA and MRA are preffered.
Hybrid substraction:
combination of temporal subtraction + dual energy
DEB
drug-eluting balloons - angioplasty balloon covered with an anti-proliferative drug which is released into the vessel during inflation of the balloon.
SyngoiFlow:
new digital DSA software - Help with visualization and improve diagnosis. - Automates the process to produce a color image highlighting the pat of the contrast medium.
PTA-POBA
percutaneous transluminal angioplasty - plain old balloon angioplasty
Sidewinder
selective or super-selective depiction of vessel.
K-edge substraction:
substraction: removal of all x-rays from the beam except those that lie below the k-shell
Dual energy subtraction:
subtraction: elimination of motion artifacts • Higher kV image is subtracted from lower kV image
Time-interval difference subtraction:
temporal subtraction - cardiac imaging (rapid motion) • Consecutive previous frame is subtracted from current frame
Mask-mode substraction
temporal subtraction - most widely used • First image: stabilize the exposure factors • Second image: stored as mask image • Mask image is subtracted from subsequently acquired images (1-6 images per sec)
Diagnostic:
thrombosis, aneurysm, arterial dissection, non-traumatic SAH, AVM, AVF, tumour vascularity • Rarely for diagnostic purpose anymore, CTA and MRA are preffered.
o Pigtail catheter:
typically used for an overview angiography.