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Vascular Term 3 > Intracranial Doppler (Midterm) > Flashcards

Intracranial Doppler (Midterm) Flashcards

1
Q

what is TCD (transcranial doppler)?

A

Noninvasive method for assessing cerebral hemodynamics and Evaluating intracranial cerebrovascular disease

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2
Q

what are used in TCD?

A

power doppler
duplex sonography
contrast agents

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3
Q

what applications are required for TCD?

A

large signal -to- noise ratio

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4
Q

do transcranial instrumetns have a higher or lower bandwidth?

A

lower

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5
Q

what is the transcranial sample volume?

A

Larger less defined sample volume than most other pulsed doppler devices

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6
Q

what freqency is necessary for TCD?

A

2-MHZ pulsed range gated Doppler device with good directional resolution is necessary

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7
Q

what power is transmitted in TCD?

A

10 and 100 mW/cm/s

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8
Q

how far from the probe do we focus in TCD?

A

40-60 mm

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9
Q

what are the indications for TCD?

A
  • Detection of intracranial stenosis and occlusions in the major arteries
  • Evaluation of intracranial hemodynamics and collateral flow where there is extracranial disease
  • Monitoring of intracranial vessel recanalization in acute stroke
  • Monitoring intracranial hemodynamics
  • Detection of right to left shunts
  • Detection of cerebral microemboli
  • During functional tests
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10
Q

when do we monitor intracranial hemodynamics?

A

after:

  • hemorrhage
  • endarterectomy/angioplasty
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11
Q

what functional tests may we use TCD during?

A
  • Stimulation with vasoconstrictive drugs
  • External stimulation of visual cortex
  • Before neurosurgery
  • During open heart surgery
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12
Q

what must a sonographer have a knowledge of in TCD study?

A
  • Probe and settings
  • Circle of Willis anatomy
  • Appropriate patient positioning
  • Nomenclature of cerebral arteries
  • Normal depths of vessels
  • Normal velocities of vessels
  • Low resistant flow signals
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13
Q

how many segments does the ACA have?

A

2 (A1 and A2)

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14
Q

where is the carotid siphon?

A

just proximal to ICA intracranial branches

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15
Q

how many segments are in the carotid siphon?

A

3 (C1 and C2 and C3)

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16
Q

where does the ophthalmic artery branch?

A

junction of C2 and C3

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17
Q

how many segments does the MCA have?

A

2 (M1 and M2)

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18
Q

how many segments does the PCA have?

A

2 (P1 and P2)

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19
Q

where are segments 1 located?

A

closest to midline of the brain

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20
Q

what are the 4 ultrasonic windows for TCD?

A

Temporal approach
Orbital
Submandibular
Suboccipital

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21
Q

where is the probe directed in the submandibular approach?

A

The probe is directed upward toward the proximal intracranial ICA

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22
Q

where is the submandibular window located?

A

below the mandible at the angle-using the carotid triangle

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23
Q

how is the patient lying for the suboccipital approach?

A

-Patient is positioned lying on their
left side,with back toward you
-Head must be tucked in at the chin
toward the chest

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24
Q

where is the probe located in the suboccipital approach?

A

Probe is placed at the base of the skull
and directed upward into the
foramen

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25
Q

what is seen in the transorbital approach?

A

carotid siphon and opthalmis artery

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26
Q

where is the probe directed in the transorbital approach?

A

Probe is directed toward the orb to locate the OA,then followed to the carotid siphon-distal intracranial ICA

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27
Q

how is the patient laying in the transtemporal approach?

A

patient in supine position

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28
Q

where is the probe places (average) for transtemporal approach?

A

Probe is placed on temporal aspect of head Cephalad to zygomatic arch
-Immediately anterior and slightly superior to tragus of ear

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29
Q

which position of the transtemporal apprach is the most adequate?

A

Position 1 of the image is most often adequate as a window

Immediately anterior and slightly superior to tragus of ear

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30
Q

what do we visualize in the anterior orientation of transttemporal approach?

A
  • M1and M2 segments of MCAS
  • C1 segment of carotid siphon(CS)
  • A1 segment of ACA & anterior communicating artery
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31
Q

what do we visualize in the posterior orientation of transttemporal approach?

A
  • insonates P1 and P2 segments of PCA

- Top of the basilar artery and the posterior communicating arteries

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32
Q

what is the Suboccipital-transforaminal approach essential for?

A

screening distal vertebral arteries(V4 segment) and the Basilar artery throughout its entire length

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33
Q

where is the probe placed for the Suboccipital-transforaminal approach?

A

between the posterior margin of the foramen magnum and the spinous process of C1 vertebra

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34
Q

where is the beam aimed for the Suboccipital-transforaminal approach?

A

aimed at the bridge of the nose

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35
Q

who pose a difficulty for the Suboccipital-transforaminal approach?

A

elderly individuals or arthritic necks

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36
Q

what can be insonated in the transorbital approach?

A
  • The opthalmic artery can be insonated as well as components of the anterior cerebral circulation
  • Not used as much as the transtemporal and suboccipital approach
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37
Q

what is the submandibular useful for?

A
  • Useful compliment to extracranial studies
  • Probe is placed in the retromandibular area
  • Useful for detecting carotid dissection-and chronic ICA occlusion with collaterals
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38
Q

insonation depth for the transtemporal arteries?

A 
MCA-50
ACA-70
Carotid siphon-65
PCA-65-70
Basilar- 75
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39
Q

velocities for transtemporal areries?

A 
MCA-55
ACA-50 
Carotid siphon-39
PCA-40
Basilar-40
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40
Q

how do you identify cerebal vessels?

A
  • Insonation depth
  • Direction of flow at insonation depth
  • Flow velocity(mean flow velocity and systolic or diastolic peak flow velocity)
  • Probe position ie- what window is being used
  • Direction of the ultrasonic beam ie-posterior,anterior,sub-occipital,submandibular
  • Traceability of vessels
  • Low resistant flow spectrum similar to ICA flow
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41
Q

what is an important factor when identidying cerebral vessels?

A

Low resistant flow spectrum similar to ICA flow

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42
Q

what approach do you start with in the exam?

A

transtemporal

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43
Q

how do you start the exam?

A
  • Start with the transtemporal approach
  • Identify the midline of the brain
  • If the midline is not visible,then the exam may be futile
  • Once it is identified,turn on the color
  • The MCA is identified on either side of the midline at a depth of 50-55 mm
  • Track the ipsilateral arterial network,by angling he probe anteriorly toward the ACA and then posteriorly toward the PCA
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44
Q

what does traceability refer to?

A

Refers to the fact the MCA and the other arteries can be tracked in incremental steps from a more shallow insonation depth(35mm) to deeper sites(55mm)

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45
Q

is flow normally toward or away from the transducer?

A

Flow is normally toward the probe as the MCA flows out toward the cerebrum

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46
Q

what may indicate disease?

A

Changes in the character of the flow profile and flow direction

47
Q

what indicates insonation of A1 segment?

A

When tracking the MCA medially(65-70mm depth),an abrupt change in flow direction-away from the probe-indicates

48
Q

at 65-70mm depth what does flow towards the probe usualy emanate?

A

usually emanate from the carotid siphon at its junction with the MCA

49
Q

when can you pick up the P1 segment of the PCA with the transtemporal appraoch?

A

By angling the beam more posteriorly from this transtemporal approach

50
Q

what is an important feature for identifying the PCAs?

A

The PCA can be tracked medially to its junction with the basilar artery and from there to the contralateral PCA

51
Q

why is hemodialysis created?

A

sustain patients with end stage renal disease

52
Q

what does hemodialysis remove?

A

waste products
creatinine
urea
excess water

53
Q

what are patients with hemodialysis likely to undergo?

A

multiple revisions, fistulas, grafts

54
Q

what is the role of the sonographer pre-operative for hemodialysis?

A

Assess arterial inflow and to determine the suitability of efferent(outflow) veins for hemodialysis access creation

55
Q

what is the role of the sonographer for post-operative for hemodialysis?

A
  • Assess fistulas and grafts for defects,stenosis or occlusion
  • Evaluate the access for aneurysms,pseudoaneurysms and perigraft abscess
56
Q

what are the indications for a hemodialysis?

A
  • Pre-op assessment
  • Distal limb ischemia
  • Absence of palpable fistula “thrill”
  • Peri-graft fluids or mass
  • Poor dialysis
  • Elevated pressures during dialysis
  • Access recirculation of 12% or greater
  • Unexplained urea reduction ratio <60%
  • Difficult cannulation or thrombus aspiration
57
Q

what are the 3 types of access for hemodialysis?

A

1-Central venous catheter
2-synthetic AV bridge graft
3-primary AV fistula

58
Q

what does an access for hemodialysis create?

A

creates a way for blood to be removed from the body, circulate through the dialysis machine, and then return to the body at a rate that is higher than can be achieved through a normal vein

59
Q

what are other names for an access?

A

fistula or shunt

60
Q

what is the insertion point for a central venous cathedar?

A

IJV or subclavian vein

61
Q

is central venous cathedar a long or short term solution?

A

short term solution

62
Q

why is central venous cathedar sometimes tunneled under the skin?

A

to be less obstructive and for easier access

63
Q

what is a primary AV fistula?

A

a surgical procedure
that creates a direct connection between
an artery and a vein

64
Q

where is a primary AV fistula done?

A

often done in the lower arm but can be done in the upper arm as well

65
Q

what is the preferred type of vascular access?

A

primary AV fistula

66
Q

what is another name for priary AV fistula?

A

Native access fistula

67
Q

which arm is the primary AV fistula usually created?

A

non-dominant arm

68
Q

what is the Primary AV fistula called?

A

Brescia-Cimino fistula

69
Q

what fistula is usually created in primary AV fistula?

A
  • Radial artery to Cephalic vein fistula is most common

- Brachial artery to Basilic vein is also common

70
Q

AVF are _______ and known for________________

A

AVF are autogenous and known for long term patency and low complication rate

71
Q

why must AVF be allowed to mature prior to use?

A

adequate flow volume may not occur

72
Q

When the fistula is created,and has matured ,the superficial efferent vein is used for __________

A

dialysis puncture

73
Q

when and why does the superficial efferent vein become lumpy and sausage shaped?

A

increased intraluminal pressure when the fistula is created

74
Q

when are flow volumes difficult to obtain?

A

difficult to obtain in the efferent vein due to inconsistent vein diameter

75
Q

what do we do when a patients arm veins are not suitable for creating a fistula?

A

synthetic bridge graft
-a surgeon can use a flexible rubber tube
to create a path between an artery and vein and the graft sits under the skin

76
Q

how is synthetic bridge graft different from fistula?

A

Used in much the same way as the fistula except that the needles used for hemodialysis are placed into the graft material rather than the patient’s own vein

77
Q

where is the synthetic tube graft placed?

A

between an artery and vein

78
Q

synthetic tube graft is used for __________

A

dialysis puncture

79
Q

when is tube graft used?

A

when veins are not adequate

-useful when fistulas have failed

80
Q

how many people are not canidates for AVF?

A

50%

81
Q

what is a synthetic graft made out of and its shape?

A

teflon (gore-Tex) and sometimes polyurethrane and may be straight or looped

82
Q

what can some synthetic access grafts be used for?

A

Some are self sealing and can be used for cannulation soon after implantation

83
Q

how do synthetic graft tubes reduce flow volume?

A

may be tapered at the arterial end

84
Q

does AVF or grafts have a shorter duration and lower patency rate?

A

grafts

85
Q

where are grafts and fistulas usually created?

A

initially in the forearm

86
Q

what happens when grafts and fistualas fail?

A

more proximal vasculature is used to create a new access

87
Q

what are other access locations for synthetic access grafts?

A
  • Brachial A to Basilica V
  • Subclavian A to Jugular v
  • Femoral A to Long saphenous V
88
Q

what are complications with a graft and fistula?

A
  • thrombus/occlusion
  • stenosis
  • Arterial steal:may result in digit or hand ischemia
  • Distal venous hypertension
  • Aneurysms and pseudoaneurysms(common)
  • Elevated right heart pressure due to excessive graft flow
  • Infection(mostly with synthetic grafts)
89
Q

where are stenosis locations within a graft or fistula?

A
  • proximal and distal anastomosis
  • within the graft
  • in venous outflow tract due to intimal hyperplasia or thrombus
90
Q

what is the sonographers role for fistulas and grafts?

A
  • Must be aware of the type of graft prior to exam
  • 2-D images to R/O visible thrombus
  • Doppler to demonstrate patency,stenosis,or occlusion
  • Aneurysms and pseudoaneurysms must be ruled out
91
Q

what is the normal spectral doppler for the feeding artery?

A

monophasic with large diastolic component

92
Q

what is the normal spectral doppler for the anastomosis?

A

perivascular tissue vibration;turbulent flow over long stretch

93
Q

what is the normal spectral doppler for the draining vein?

A

pulsatile flow-arterialized

94
Q

what should the volume flow be in graft and fistula?

A

500ml/min

95
Q

what is done after several years of use with fistula or graft?

A

Dilatation of feeding artery and draining vein after several years of use

96
Q

what are indications for looking at the graft and fistula?

A
  • Difficulty with needle placement
  • Increased dialysis time
  • Pain, swelling, or discoloration of the limb or digits (fingers/toes)
  • Loss of pulse in the graft
  • Palpable mass in the graft or limb
  • Abnormal lab values
  • Increased venous pressure during dialysis
97
Q

what should the flow be in a graft and fistula?

A

artery side to venous side

98
Q

what resoltuion is used when looking at a graft or fistula?

A

9 MHz

99
Q

what do we evaluate with graft?

A
  • Artery feeding the graft
  • The arterial anastomosis
  • The graft body
  • The venous anastomosis
  • The draining vein
100
Q

where is doppler and PSV assessed within a graft?

A
  • 2 cm cranial to the arterial anastomosis within the feeding artery
  • 2 cm caudal to the venous anastomosis within the graft
  • At the arterial and venous anastomoses
  • Mid graft
  • A PSV ratio is calculated at the anastomosis and at any visible stenosis
101
Q

what PSV shows a >50% diameter reduction

A

PSV ratio >2

102
Q

whar PSV shows a >75% diameter reduction

A

PSV ratio with a 75% stenosis

103
Q

how is diameter reduction confirmed?

A

angiography

104
Q

what should be evaluated for respiratory phasicity and transmitted cardiac pulsations?

A

The IJV adn SCV

105
Q

in the presence of an uper arm graft, what may be seen in the SCV in the absence of a central stenosis?

A

monophasic flow

106
Q

what is monophasic flow is SCV related to?

A

This is related to the high volume of blood flow and low resistance pattern of flow in the graft

107
Q

when does an arterial steal distal to the arterial anastomosis occur?

A

when the venous outflow from the graft exceeds the capacity of the inflow artery

108
Q

what does arterial steal cause?

A

cause symptoms of arterial insufficiency,particularly during dialysis

109
Q

where is doppler spectral assessed for arterial steal?

A

from the radial artery caudal to the graft insertion-usually at the wrist

110
Q

what is complete steal?

A

the direction of flow is reversed caudal to the graft

111
Q

what is partial steal?

A

The spectral waveform is biphasic(some flow on both sides of the baseline)

112
Q

what is asymptomatic steal common with?

A

no clinical significance

113
Q

what may symtomatic patients for arterial steal require?

A

graft ligation

Vascular Term 3 (8 decks)

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