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BRB Midterm > Imaging > Flashcards

Flashcards in Imaging Deck (17)
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1

What is CT?

-use ionizing radiation
-based on tissue attentuation (density) - grey scale diff tissues. Hyperdense = BRIGHTER
-Multidetector CTs: allow reconstruction, faster, physiology b/c look at multiple slices
-Contrast-enhanced CTs (CT myelography): better visualiztion of targeted tissue

2

Adv and Disadv of CT?

Adv:
-fast
-available
-can scan multiple parts of body
-reconstruction
-allows rapid diagnosis
-good for bony details

Disdv:
-radiation
-contrast agent > renal dysfnc

3

2 types of CT windowing

1. Soft tissue algorith: kernal
-standard for head
-good for soft tissu
-poor for bones

2. Bone window "kernal"
-good for bones

4

Uses of CT

-fractures (bone/calcifications = white)
-acute trauma: acute blood = white
-acute hemorrhage
-acute stroke

5

What is MRI?

-magnetic resonance, proton directions
-differentite by pulse length, f, type
-T1: spin-lattic relaxation time (longitudinal). fluid = DARK
-T2: spin-spin relacation time (horizontal). fluid = BRIGHT

6

What is contrast enhanced MRI?

-use gadolinium in T1 weighted
-if brain tissue is bright = leaking of blood brain barrier
-fat-suppressed since fat is also bright on T1

7

What is bright on T1-weighted MRI?

-fat
-melanin
-Ca
-high protein
-subacute blood (Met-hb)

8

What is bright on T2weighted MRI?

-most pathologies
-normal CSF
-EXCEPT:
-old blood (hemosiderin), Ca, air = dark on T2

9

What is FLAIR? When is it used?

-Fluid attenuation inversion recovery MRI
-nulls CSF signal
-lesion = BRIGHT
-used for MS, white matter lesions
-good for lesions close to brain-CSF (ex: near ventricles)

10

What is DWI? When is it used?

-Diffusion-weighted imaging using MRI
-calculates restricted movement (stroke = BRIGHT)to differentite cytotoxic vs vsogenic edema. based on NaK pump activity.
ex: stroke: NaK pumps fail, water enter cells, see swelling - BRIGHT
-apparent diffusion coefficient map use mathematical summation of images to overcome artifacts > INFARCT on ADC = DARK
-used for acute stroke
-fast
-BUT can be used in first 7-10 days of stroke (afterwards, DWI - no longer bright; ADC - stroke is bright)

-good for ischemic strokes, BBB breakdown, inflmation, tumour

11

What is GRE nd SWI? when are they used

-gradient echo and susceptibility-weighted imaging in MRI
-micro-hemorrhages, chronic hemorrhages
-make BRIGHTER more obvious but resultant is larger than true lesion

12

Adv and disadv of MRI?

Adv:
-good for subacute to chronic setting
-small strokes, lacunar strokes
-no radiation
-good detail

Disdv:
-long
-not good for acute/unstable
-not as available
-contraindicated with pacemakers
-claustrophobia

13

How can we image vessels?

1. ultrasound
2. CT angiography
3. MRi angiography

14

What is doppler ultrasound? Use?
Adv and Disadv

-use sound energy
-blood: hypoechoic (dark)
-tissue: hyperechoic (bright)
-flow analysis to determine STENOSIS
Use: neck region (ICA, VA)

Adv:
-available
-stroke: subacute, chronic in neck

Disadv:
-long
-Not good to penetrate bones

15

What is CT angiography? Use?
Adv and Disadv

-MDCT
-IV contrast
-quick scan: seconds
-reconstruction

16

What is MR angiography? Use?
Adv and Disadv

-MRI with/ without contrast
-good resoluation
-no radiation
-fast: minutes
-same disadv as normal MRI

17

Catheter Angiography? Use?

-minimally invasive
-enter via femoraal, radial, or brachial As to brain
-inject contrast
-use Xrays
Use: endovscular tx for arterial disease