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RAD413 > Digital subtraction angiography > Flashcards

Digital subtraction angiography Flashcards

1
Q

what is DSA

A

digital subtraction angiography

  • fluoroscopic technique extensively used in IR for visualising blood vessels
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2
Q

what is DSA good for

A

navigation of wires and catheters through vasculature to various areas of the boduy

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3
Q

radiopaque structures such as bones are eliminated digitally from image allowing for accurate depiction of blood vessels

A
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4
Q

why cant normal fluoroscopic imaging be used to view vessels

A
  • small vasculature will be obscured by patients bones and soft tissue
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5
Q

what is the procedure to acquiring a DSA sequence

A
  1. patient positioned normally with vasculature in view
  2. acquisition run, first few images taken should not have contrast
  3. that first image is used to select appropriate kV and mA
  4. second image is ‘mask’ image
  5. now contrast is injected and images are taken. these are ‘fill’ images. (these images record the passage of contrast through vessels)
  6. real time subtracted images are created by subtracting the ‘mask’ image from subsequent ‘fill’ image
  7. assuming no movement from patient, images in run should show contrast filled vessels only with no other overlying anatomy
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6
Q

what is DSA roadmap?

A
  • once you have a series of subtracted images, you pick an image that shows the best view of the vessel of interest
  • image selected is overlaid onto of live image of patient when you next start screening
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7
Q

why is DSA roadmapping done

A
  • this alone with contrast acts as a guide to navigate through the vessels
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8
Q

if DSA roadmapping cannot be done, what is done alternatively

A
  • ‘blind’ navigation
    or
  • constant flow of contrast running through patient vessels
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9
Q

why is using constant flow of contrast through vessels to aid navigation bad

A
  • procedure would take hours and you would damage patient kidneys with the amount of contrast used
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10
Q

what is the movement artefact found in DSA

A
  • when patient moves between the acquisition of the mask and fill images
  • creates a misregistration between pixels in mask and pixels in fill
  • as the pixels are in different positions/misaligned in the mask and fill image, correct subtraction will not occur
  • anatomical background will not be competed removed
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11
Q

how can you reduce motion artefact in DSA

A
  • remasking
  • new frame is closed from beginning of sequence
  • new frame must be further into sequence than original mask image but before the vessels are filled with contrast
  • with appropriate frame, this is the new mask image to be used in subtraction
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12
Q

what is another method of dealing with movement artefact and what is this

A
  • pixel shifting
  • radiographer manually shifts mask image in small increments in order to minimise the mis-registration of pixels
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13
Q

DSA is great for viewing vessels, but why is this not used in the catheter lab?

A
  • pixel shifting cannot be done for movements such as peristalsis of bowel
  • as there will always be a degree of movement and pixel shifting cannot correct the issue
  • inability of pixel shift movement is why DSA is pointless in Cath lab due to constant cardiac movement
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14
Q

what is rotational angiography

A
  • 3D rotational angiogrpahy
  • c-arm rotates around patient acquiring multiple xray images
  • images from different angles are reconstructed to form 3D image

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15
Q

what is 3D overlay and what does this help with

A
  • superimposition of 3D volume data (ct reconstructions) on live fluro display
  • provides more info on patient anatomy and helps with navigation through complex anatomy
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16
Q

why is 3D overlay efficient

A
  • brings advantage of other imaging modalities e.g MRI/CT
  • make most out of available pre-procedural info and avoid radiation dose and contrast injections for repeating scans
17
Q

what is a hybrid theatre

A
  • combined operating theatre and IR suite
  • used when IR is needed in surgery
  • provides optimal efficient patient care
18
Q

give an example of a case that would require the hybrid theatre

A

endovascular aortic repair (EVAR)

-need xrays to guide graft into aneurysm through incisions

19
Q

what technique is used for vascular navigation during angiopgrpahy

A

seldinger technique

20
Q

explain the procedure of using seldinger technique for vascular guide/insertion

A
  1. seldinger needle inserted into vessel under US guidance
  2. guidewire inserted through center of hollow needle, into vessel
  3. needle withdrawn and guide wire left in vessel
  4. sheath is slid over guide wire. Sheath stays in place throughout procedure maintaining access to vessel and allowing to slide larger items e.g catheter and stents over guide wire
21
Q

how can you tell that you have correctly inserted the needle into a vessel

A
  • there will be flashback of blood
22
Q

what compartment of the sheath prevents leakage of blood

A

end of sheath has a valve which prevents blood leakage

23
Q

what is the most commonly used artery for access for angiography

A
  • common femoral artery in the groin
24
Q

the kit :
- xray
- US
- catheter
- wires
- stents
- coils

A
25
Q

what are the 3 ways to close a puncture site

A
  1. manual pressure (10 mins)
  2. pro glide (internal suture)
  3. angioseal (collagen plug)
26
Q

what is angioplasty

A

surgery using wires, catheters, gallons and stents to reduce the narrowing and restore blood flow in vessels

27
Q

how is a balloon catheter used to remove blockage in artery

A
  • wire is passed through blockage
  • radiologist then passes balloon catheter over wire
  • balloon inflates inside blocked vessel to stretch and decrease narrowing
28
Q

what is AAA

A
  • abdominal aortic aneurysm
  • due to atherosclerosis buildup causing walls of abdominal aorta to be weak and bulge outward like a ballon
29
Q

what equipment would be used for an AAA and how

A
  • graft that has been pre packed into catheter is introduced into artery in groin
  • under xray guidance, advances into aneurysm and deployed where it expands to fit within aorta
  • blood will now flow through stent and reduce affect on weak wall of aorta/aneuryms
30
Q

what equipment would be used for a brain aneurysm and how

A
  • small metal coil inserted into aneurysm through arteries running from groin to brain (prevent opening skull)
  • stop blood flowing into aneurysm so weak wall won’t burts
31
Q

what software is used to analyse how much brain function is left after a thrombosis in brain

A

brainomix

32
Q

what is a thrombectomy

A
  • use specially designed clot removal device inserted through catheter to pull or such out clot to restore blood flow
  • aspiration may be used along side, as stand reciever surrounds and traps within cloth, suction can be applied simultaneously to ensure the clot doesnt travel anywhere else
33
Q
A

RAD413 (24 decks)

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