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STP 1st year exams > Vascular > Flashcards

Vascular Flashcards

1
Q

Effect of age on arteries:

A

Arteries have properties to allow circulation propagation - as you get older these properties are lost, calcification occurs and vessels become less elastic = disease

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2
Q

proximal =

A

towards heart

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3
Q

distal =

A

away from heart

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4
Q

antegrade flow =

A

away from heart

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5
Q

retrograde flow =

A

towards heart

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6
Q

arteries and veins have 3 layers

A

intima, media, adventitia

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7
Q

intima

A

inner layer of vessel

vascular endothelium - provides lubrication

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8
Q

media

A

middle layer of vessel

made of elastin, collagen, layers of smooth muscle

provides elasticity

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9
Q

adventitia

A

outer layer of vessel

strong thick collagen layers with some elastin

fixes arteries in place

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10
Q

vein walls

A

walls are thin and very elastic

media and adventitia are less well-defined

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11
Q

distal veins have…

A

valves

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12
Q

the trunk or portal venous system do not have…

A

valves

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13
Q

How big are arterioles? What are walls made of? What do they do?

A

<1mm diameter

smooth muscle

control flow to distal capillary beds

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14
Q

Aorta =

A

The main artery that comes out of heart - main blood vessel that supplies body with blood (oxygen).

It runs straight down the centre of the body – sits just in front of spine, slightly to the left.

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15
Q

Ascending aorta

A

comes straight out of heart and into the aortic arch

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16
Q

Abdominal aorta splits into…

A

bifurcates into left and rigth common iliac arteries (at the level of the belly button to supply both legs with blood)

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17
Q

the thoracic aorta becomes the abdominal aorta at the level of the…

A

diaphragm

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18
Q

Abdominal aorta can be further divided into…

A

suprarenal = above kidney

Infrarenal aorta = below the renal arteries which supply blood to the kidneys

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19
Q

The abdominal aorta

A

Continuation of the descending thoracic aorta

Supplies all of the abdominal organs and the under surface of the diaphragm and parts of the abdominal wall. Its terminal goes on to supply the pelvis and lower limbs

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20
Q

the normal diameter of the abdominal aorta =

A

<2cm in diameter

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21
Q

Ultrasound: vein vs artery

A

arteries have thicker more muscular walls than veins

veins are easily compressed

central venous structures will fluctuate in size with respiration

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22
Q

Definition of an aneurysm:

A

An abnormal dilatation of a blood vessel by more than 50% of its normal diameter.

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23
Q

What diameter is considered an AAA?

A

> 3cm

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24
Q

When is an AAA at risk of rupture?

A

> 5.5cm

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25
Q

If AAA ruptures…

A

causes massive internal haemorrhage = patient needs urgent 2-week wait referral to vascular surgery to discuss elective repair

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26
Q

What is the cause of AAA?

A

atherosclerosis

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27
Q

What are the risk factors for AAA?

A

smoking is biggest risk factor
age
males at higher risk
PAD/CAD
family history
hypertension
high cholesterol
connective tissue disorders

diabetes is protective - slower AAA growth

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28
Q

Pathophysiology of AAA:

A

dilation/swelling of the aortic wall causes gradual weakening due to inflammation, oxidative stress, proteolysis and biochemical wall stress = loss of structural integrity due to reduced structural proteins (elastin + collagen)

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29
Q

there are 3 types of AAA

A

fusiform = bulges out on all sides
saccular = bulges only on 1 side
pseudoaneurysm = outer layer of aortic wall becomes dilated

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30
Q

Symptoms of AAA:

A

normal no symtoms until rupture

back pain, abdominal pain, low blood pressure, tachycardia, collapse or pulsatile abdominal mass

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31
Q

National Abdominal Aortic Aneurysm Screening Programme:

A

Men aged 65 and over

uses abdominal ultrasound scan

two anterier posterior measurements are taken (longitudinal + transverse)

Measure aorta in peak systole due to slight changes in diameter during the cardiac cycle

inner-to-inner measurements of diameter used for consistency

<3 = no anyrsuym
3-4.4 = annual survallence
4.5-5.4 = 3 monthly survallance
>5.5 = intervention

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32
Q

B mode =

A

brightness mode = grey scale 2D image

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33
Q

Curvy linear probe =

A

lower frequency = better penetration at depth at expense of resolution

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34
Q

Advantages of Ultrasound in AAA surveillance:

A
  • Non-invasive
  • Safe – no ionizing radiation
  • Quick
  • Accurate
  • Reproducible – can show increases in AAA over time
  • High patient acceptance – just cold jelly on skin
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35
Q

Limitations of Ultrasound in AAA surveillance:

A

obesity - aorta sitting deeper

excess bowel gas can cause acoustic shadowing (ultrasound can not pass through gas)

variation of aortic diameters with the cardiac cycle

no visualisation of the thoracic aorta

inter-operator and intra-operator variability

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36
Q

When is intervention used for an AAA?

A
  • Asymptomatic and 5.5 cm or larger
  • Symptomatic AAA
  • Asymptomatic, larger than 4.0 cm and has grown by more than 1 cm in 1 year
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37
Q

Types of AAA intervention:

A

open surgery (invasive, higher risk and longer recovery so only used when appropriate)

endovascular aneurysm repair (EVAR) = used when comorbidities or anesthetic risk = uses catheter and stent graft

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38
Q

EVAR has risk of..

A

endoleaks = requires yearly monitoring

AAA open surgery thus has better outcomes long term

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39
Q

Endoleak

A

complication of EVAR (endovascular aneurysm repair)

blood flows outside of stent but within aneurysm sac

can be better detected using contrast-enhance ultrasound (microbubbles injected into bloodstream)

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40
Q

Thrombus =

A

blood clot

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41
Q

Blood clots (thrombus) forms due to…

A

Virchow’s Triad

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42
Q

Virchow’s Triad =

A

1) blood stasis

2) changes in vessel wall (damage)

3) thrombogenic changes in blood (hypercoagulability)

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43
Q

Blood stasis

A

free-flowing blood doesn’t clot

blood can get caught in areas and pool

external compression can cause clotting – e.g. tumours/pregnancy/muscle swelling after extreme weight lifting

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44
Q

May-Thurner Syndrome

A

Left iliac vein is compressed by the right iliac artery = Artery is sitting over top of iliac vein, causing vein compression + repeated strain = blood will clot = DVT

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45
Q

Things that trigger the Virchow’s triad

A
  • major trauma
  • congestive heart failure (inefficient pump) = oedema in legs, cooling of blood in reservoirs (veins)
  • previous history
  • central venous catheters
  • hormone therapy
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46
Q

embolus =

A

detached mass able to travel in a vessel

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47
Q

embolism =

A

lodging of an embolus

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48
Q

Thrombo-embolism =

A

blockage by a thrombus that has travelled

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49
Q

Venous Thrombo-Embolic Disease (VTE):

A

Deep Vein Thrombosis (DVT) – usually in the lower limb

Pulmonary embolism (PE) - Sudden and life-threatening

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50
Q

DVT

A

Calf is painful, swollen, hot with reddened skin

Vein is non-compressible

Swelling around vein – oedema

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51
Q

Risk factors for Venous Thrombo-Embolic Disease (VTE):

A

surgery

immobility = sedentary lifestyle, elderly, surgery

age

malignancy

pregnancy

varicose veins (may not be causal)

thrombophilia (blood more likely to clot)

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52
Q

DVT NICE guidelines:

A

When DVT is suspected, the 2 level DVT Wells score is used to estimate the clinical probability of DVT.

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53
Q

Patients with a likely DVT Wells score (2 points or more):

A

A proximal leg vein ultrasound scan, with the result available within 4 hours if possible

A D dimer test if the scan result is negative, then offer a repeat proximal leg vein ultrasound scan 6-8 days later.

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54
Q

Why do DVTs need to be treated?

A

DVT can embolise to lungs = life-threatening

Blood clot in leg causes scaring = venous pooling = venous hypertension = cascade of inflammation = ulcer

Patients can develop Post Thrombotic Syndrome (PTS)

Normally working people are effected = significant impact to NHS costs but also independence/earning potential

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55
Q

Post Thrombotic Syndrome (PTS)

A

chronic pain and swelling, venous congestion, oedema, ulceration

different than claudication – Claudication is reproducible (same aggravating factor (walking) and same relieving factor (rest). Whilst PTS feels like leg is going to burst.

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56
Q

Management of DVT:

A

Elevation – gravity to help drainage

Stockings – compress leg to reduce swelling (improved blood flow)

Anticoagulation - thins blood to prevent clot forming (reduces further risk of VT)

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57
Q

Invasive intervention of DVT:

A

Remove the clot and restore blood flow

  • Mechanical thrombectomy
  • Thrombolysis infusion via venous catheter
  • Angiojet / mechanical assisted lysis / EKOS (endovenous ultrasound-assisted)
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58
Q

Varicose veins:

A

Effects superficial (surface level) veins

Characterised by enlarged tortuous veins and failure of valves

Causes aching heavy legs

faulty valves

weak walls

failure of calf muscle pump

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59
Q

aetiology of varicose veins?

A

Unknown

?DVT

?occupational standing

?obesity

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60
Q

Venous Incompetence results in…

A

venous hypertension

  • pigmentation
  • ulceration
  • lipodermato-sclerosis or woody leg –thickening
  • varicose eczema- leaking components – inflame -
  • mis-shaping-“inverted champagne bottle”
  • swelling
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61
Q

Venous ulceration =

A

painless

wet/weeping

tissue hardening

hyperpigmentation

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62
Q

arterial ulceration =

A

painful

necrotic edges

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63
Q

Varicose veins treatment options:

A
  • Endovenous ablation
  • Foam Sclerotherapy
  • Surgery / Stab avulsions
  • Pull vein out of leg
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64
Q

Lower limb vein disease:

A

DVT

Telangiectasia

Superficial Thrombophlebitis

Kippel-Trenaunay-Weber Syndrome

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65
Q

Telangiectasia =

A
  • SPIDER VEINS
  • sun damage
  • post radiation
  • NOT LIFE THREATENING
  • venous hypertension
  • chronic flushing
  • not treated on NHS? laser?
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66
Q

Superficial Thrombophlebitis =

A

Superficial vein thrombosis

inflammation of vein caused by clotting

painful in the inflammatory phase

feels like hard lumpy ‘rope’ under skin

episodic

complication of varicose veins

does not usually progress to DVT but can

IV drug use

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67
Q

Kippel-Trenaunay-Weber Syndrome =

A
  • rare congenital condition
  • port wine stain
  • varicose veins
  • hypertrophy of soft tissue and bone locally
  • underdeveloped lymph system
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68
Q

Carotid artery stenosis =

A

the internal carotid artery and vertebral arteries supply the brain

high velocities are associated with stenoses

stenosis can lead to embolisation, TIA and stroke

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69
Q

Stroke can be…

A

Hemorrhagic (15%) = caused by a burst blood vessel - blood pools in brain, causing a buildup of pressure on the brain.

ischemic (85%) - blood flow is blocked plaque build up, thrombosis (plaque rupture and blood clot formation) or embolism (clot breaks off from somewhere else)

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70
Q

Risk factors for stroke are same as….

A

PAD

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71
Q

Carotid plaque

A

When there is stenosis (narrowing), blood is forced through narrow gap = high velocity = plaque more likely to be dangerous as more likely that emboli will travel up to brain.

72
Q

neural crossover:

A

side of brain damaged is opposite to the side of body displaying symptoms

73
Q

Stroke symptoms on left side of the body suggests…

A

right side of brain effected = blood supply to the right side of the brain is stopped.

right side of the brain is in charge of the left side of the body

look for right carotid disease

74
Q

Symtoms of stroke and TIA

A

one sided weakness -
face/arm/leg numbness

Aphasia – loss of speech, coordination

Visual loss, double vision, amaurosis fugax

Symptoms last for 24hrs = stroke

Symptoms last less than 24hrs = TIA

75
Q

Amaurosis fugax =

A

temporary and painless loss of vision - caused by a blockage of blood flow to the retina (ophthalmic artery)

76
Q

Vertebro-basilar disease =

A

poor blood flow to the posterior (back) portion of the brain, which is fed by two vertebral arteries that join to become the basilar artery

dizziness + loss of balance

77
Q

TIA (transient ischaemic attack) =

A

acute non-disabling stroke

<24 hours, often much less

78
Q

Investigating carotid disease: Proximal arteries (aortic arch, proximal subclavian, brachiocephalic /innominate) are scanned using…

A

MRA - magnetic resonance angiography

CTA - Computed Tomography Angiography

79
Q

Investigating carotid disease: the Intracranial arteries (MCA, PCA, ACA, BA) + Extracranial arteries (carotid arteries, vertebral arteries, subclavian) are scanned using…

A

Transcranial Doppler ultrasound

MRA

CTA

80
Q

Ultrasound of diseased carotid arteries:

A

Plaque appearance can be hyperechoic (bright) or hypoechoic (dark).

The significance of a plaque may not clear from B-mode alone = Need colour and Doppler waveforms to establish significance.

81
Q

Measuring stenosis in carotid arteries uses…

A

Peak systolic velocity

end diastolic velocity

82
Q

Flow in the internal carotid artery and in the vertebral arteries is…

A

continuous throughout diastole: constant, steady perfusion of the brain

83
Q

Treatment of stroke/TIA:

A

aspirin

carotid endarterectomy benefits patients with SYMPTOMATIC significant stenoses

stenting is an alternative interventional technique

84
Q

ABPI

A

ankle brachial pressure index

used to assess peripheral arterial perfusion in lower limbs

ratio composed of blood pressure in upper arm (brachial artery) and lower limb (dorsalsis pedis in foot or posterior/anterior tibial artery in ankle)

85
Q

If there is disease present in the lower limb (stenosis or blockages in arteries), the pressure distally (at ankle) will…

A

decrease

86
Q

Equipment needed for APBI:

A

Sphygmomanometer = used to increase pressure of blood pressure cuff when measurements are taken

Hand held doppler device = continuous wave doppler

Ultrasound gel

87
Q

Performing an ABPI:

A

Rest the patient in a supine position for 10min – to normalise pressure

Measure the systolic blood pressure bilaterally (both sides) in the posterior tibial artery/anterior tibial artery/dorsalis pedis artery

Measure the systolic blood pressure bilaterally in the branchial artery

Calculate the ratio for each

88
Q

ABPI calculation =

A

highest ankle pressure / highest brachial pressure

89
Q

How to measure systolic blood pressure:

A

Inflate the cuff above the pressure at which the Doppler pulse is no longer audible and then deflate the cuff slowly, noting the pressure at which you first detect a pulse from the Doppler. This represents the systolic pressure in the vessel being assessed.

For ABPI - doppler is used to listen to pulse (amplifies sound)

90
Q

Incorrect ABPI can be measured due to:

A

Incorrectly positioned cuff

Irregular pulse (e.g. atrial fibrillation)

Calcified vessels (e.g. diabetes, renal disease) = False high readings due to non-compressible arteries.

Patient anxious and unrelaxed – increased blood pressure

Incorrect doppler probe/position of probe

91
Q

ABPI >1.2

A

Calcified vessels often cause unusually high ABPI results. In this scenario, further assessments such as duplex ultrasound and angiography are advised to accurately assess perfusion.

92
Q

ABPI 0.9-1.2

A

No evidence of significant peripheral arterial disease

93
Q

ABPI 0.8-0.9

A

Mild arterial disease

94
Q

ABPI 0.5-0.8

A

Moderate arterial disease: typically presenting with claudication

95
Q

ABPI <0.5

A

Severe arterial disease: typically presenting with rest pain, ulceration and gangrene = critical limb ischaemia.

96
Q

A 50% diameter stenosis leads to…

A

pressure drop after stenosis

due to turbulence and a loss of energy after a stenosis

97
Q

Exercise ABPI:

A

look at changes in the ABPI post exercise

if there is disease expect ratio to decrease = A drop of >0.15 in ratio after exercise compared to at rest = diseased (normal people should be same or increase)

98
Q

Vascular ultrasound uses…

A

sound waves to evaluate the body’s circulatory system and help identify blockages in the arteries and veins and detect blood clots

99
Q

why use ultrasound?

A

Ultrasound does not use ionizing radiation, has no known harmful effects, and provides images of soft tissues that don’t show up on x-ray images.

100
Q

Vascular ultrasound is performed to:

A

help monitor the blood flow to organs and tissues throughout the body.

locate and identify blockages (stenosis) and abnormalities like plaque or emboli and help plan for their effective treatment.

detect blood clots (DVT in the major veins of the legs or arms).

determine whether a patient is a good candidate for a procedure such as angioplasty.

evaluate the success of procedures that graft or bypass blood vessels.

determine if there is an enlarged artery (aneurysm).

evaluate varicose veins.

101
Q

How does ultrasound work?

A
  1. High-frequency sound waves are transmitted from a transducer.
  2. These sound waves are then reflected by different tissue types in different ways.
  3. The reflected sound waves are then picked up by the ultrasound transducer.
  4. The sound waves are then transformed into an image by special software.
102
Q

How do tissue types differ in their reflection of sound waves?

Bones, fat and stones =

A

produce a hyperechoic signal (appears bright as most ultrasound waves are reflected)

103
Q

How do tissue types differ in their reflection of sound waves?

Cartilage and muscle =

A

produce a hypoechoic signal (appears dark as most waves pass through the tissue)

104
Q

How do tissue types differ in their reflection of sound waves?

Fluid and fluid-filled structures =

A

produce an anechoic signal (appears black as there is no reflection of ultrasound waves)

105
Q

There are 3 different types of ultrasound probe:

A

Linear

Curvilinear

Phased

106
Q

linear probe:

A

High frequency (7-15MHz):

High resolution but superficial (1-6cm) depth

Good for vascular access, nerve blocks, assessment of testes and superficial lung tissue

107
Q

Curvilinear:

A

Low frequency (2-5MHz)

Low resolution, but greater depth (10-20cm)

Useful for abdominal, pelvic, obstetric and deep lung tissue

108
Q

Phased:

A

The lowest frequency (1-3MHz)

lower resolution but greater depth

Useful for echocardiography

109
Q

dot/cross/line on the probe =

A

correlates with a dot on the left side of the screen.

This marker should be toward the patient’s right in transverse and head in longitudinal.

110
Q

Gain:

A

adjusting the gain of an ultrasound changes the brightness of the image

The gain should be adjusted until fluid appears black and soft tissue appears mid-grey with some parts of the image appearing white

111
Q

Depth:

A

Depth measures are shown in cm on the side of the ultrasound monitor

112
Q

Tips for achieving optimal ultrasound view:

A

Use lots of gel

Make good contact between the probe and skin (whilst ensuring the patient is comfortable)

Dim the lights to improve your view of the monitor

Ensure the probe is perpendicular to the skin

113
Q

Doppler =

A

an ultrasound technique that evaluates movement of materials in the body. It allows the evaluation of blood flow through arteries and veins in the body.

114
Q

Doppler ultrasound can evaluate:

A

blockages to blood flow (such as clots)

narrowing of vessels

tumours and congenital vascular malformations

reduced or absent blood flow to various organs

increased blood flow (may be a sign of infection)

115
Q

what does doppler look like when there is stenosis?

A

Drop in blood pressure after stenosis causes damped waveform

Duplex ultrasound imaging can show the degree of stenosis or narrowing, the site of occlusions or stenoses

116
Q

Doppler records….

A

velocity of all RBCs

RBCs are fastest in the centre of vessel, vessel walls slow flow down = there are a range of velocities

Doppler waveform plots range of velocities (RBCs) not flow = doesn’t tell us flow but gives us an idea about perfusion

The wave tells us how many RBCs are travelling at one speed.

As ventricles contract, blood is expelled into circulation and repeats – velocity changes in a pattern.

117
Q

velocity increases when…

A

there is narrowing (area decreases) - up to a point where stenosis becomes too much (50% stenosis)

118
Q

50% diameter stenosis leads to

A

Pressure drop

Volume flow is reduced

Perfusion to tissue is reduced

119
Q

If vein doesn’t compress…

A

?thrombus/DVT

120
Q

Venous return and flow is modified by…

A
  • one way valves
  • calf pump
  • respiratory pump
  • gravity
121
Q

If venous return is impaired this can cause…

A

either dilation of veins or transfer of fluid to interstitial spaces (oedema)

122
Q

waveform repeating pattern corresponds to…

A

pulse = can be used to assess heart rate

123
Q

The diastolic component of doppler waveforms can change due to…

A

sensitive to gravity, posture, temperature, disease, peripheral resistance

124
Q

Vein doppler waveform:

A

no signature shapes like artery waveforms

lack of regular pulsatility

phasic with respiration

125
Q

incompetent veins doppler waveform:

A

change in direction of flow

126
Q

microcirculation =

A

arterioles, capillaries, venules

127
Q

There are 3 modes of ultrasound:

A

B (brightness)

Colour

Doppler

128
Q

Ultrasound waves are…

A

longitudinal: the vibration is parallel to the wave direction

Molecules vibrate and create pressure disturbances

The wave travels at the speed of sound

In soft tissue the speed of sound is constant

Sharp images (high spatial resolution) are produced with very high frequencies/small wavelengths.

129
Q

Explain ultrasound waves…

A

Particles themselves vibrates but don’t move along, the wave moves along – a disturbance causes particle to vibrate and then the wave moves. Peaks = positions where molecules are close together. Wave moves in 3D outwards from disturbance.

130
Q

ultrasound Frequency

A

Frequency is the number of cycles per unit of time

Ultrasound is 1MHz – 20MHz

131
Q

ultrasound Wavelength

A

Wavelength is length of 1 cycle (distance between peaks)

the size of the wavelength determines the resolution of the image (smaller/low wavelength = sharper image)

132
Q

Speed of sound

A

Wavelength and frequency are linked by the speed of sound. The speed of sound in all soft tissues is roughly the same (1540m/s) = allows imaging. Bone is much higher, air is much lower

133
Q

Pulse echo and reflections

A

Probe acts as both a transducer and receiver

The ultrasound machine measures the time it takes for echoes to return

strength of echo is assigned a grey level

134
Q

Probe send pulses into tissue…

A

some reflects of tissue but some carries on into tissue – we are interested in reflected pulses. When tissue changes in structure we get an echo – depending on density and stiffness. Differences in tissue properties cause reflections.

135
Q

Z =

A

acoustic property of tissue

CHARACTERISTIC IMPEDANCE = Every tissue will respond to the passage of acoustic waves in a slightly different way

This depends on physical properties of density and speed of sound and stiffness.

Differences in tissue properties, cause reflections….ECHOES

136
Q

Attenuation is frequency dependent

A

The echo strength decreases with depth

Attenuation is caused by a loss of signal

Absorption: ultrasound is converted to heat

Scattering: the pulse is re-directed into the tissue

High frequency ultrasound attenuates more than low frequency ultrasound

137
Q

High frequency/small wavelength =

A

good spatial resolution

poor penetration into tissue (attenuation)

138
Q

B-mode: blood

A

black

139
Q

B-mode: fluid

A

black

140
Q

B-mode: bone

A

bright white

141
Q

B-mode: calcified plaque

A

bright white

142
Q

Arterio-Venous Malformations

A
  • Congenital
  • “tangle” of vessels with direct arterial-venous communication
  • Most common in cerebral circulation
  • Can occur anywhere
  • Direct connection
  • Pulsatile flow in venous side
  • Often found incidentally
  • Hard to treat – can treat veins that symptomatic but will come back
143
Q

Piezoelectric Transducer =

A

transducers can both produce and detect ultrasound

the ceramic is usually made from lead zirconate titanate (PZT)

in transmission mode a voltage makes the PZT crystal change shape, and waves are formed

an incoming wave can make the PZT change dimensions and produce a voltage. The ‘echo’ is detected

The backing layer of the PZT transducer absorbs unwanted waves, and the matching layers prevent unwanted internal reflections

144
Q

ultrasound probes are made up of…

A

many transducer elements in a line (array)

145
Q

transducer elements can…

A

can both transmit waves (pulses) and detect pulses, the ‘echoes’

pulses travel in a straight line; we call this the ultrasound beam

to create one 2D image the time taken is the frame rate

146
Q

A mode

A

amplitude mode

is one line

‘strength of echo’, signal amplitude is assigned a grey level

147
Q

M mode

A

‘motion or movement’ is one line versus time

used during echo - e.g. to see opening and closing of valves

Dashed beam – one pulse travels along beam and that is plotted against time

0-10cm depth

148
Q

Framerate –

A

how long it takes to build-up 2D image

149
Q

B–mode

A

‘brightness’ (2D scan)

Skin surface is always at top of image

gives maximum signal: beam perpendicular to vessel wall

150
Q

fluid on ultrasound

A

appears black – blood, cysts, interstitial fluid

151
Q

plaque can be classified as…

A

hyperechoic (bright) - calcified
hypoechoic (dark)

152
Q

To see extent of disease on ultrasound…

A

colour Doppler and spectral waveforms can be used

153
Q

sharper image =

A

higher frequency

154
Q

vessels in a diabetic

A

arteries can become calcified = appear brighter than surrounding tissue

155
Q

Curvilinear Array

A

beams are perpendicular to probe surface

Beams are further apart at depth = spatial resolution isn’t as sharp at depth

see more but at lower resolution

156
Q

fat on ultrasound

A

cause image degradation, (diffraction and mis-registration artefacts)

images are blurred as beams are not travelling in a straight line.

157
Q

fluid on ultrasound

A

blood, cysts, interstitial fluid, oedema, lipid cores all appear black

158
Q

gain

A

intensity/brightness

159
Q

TGC control

A

Allows to increase the gain at different depths – may just want a certain section to be brighter

160
Q

phased array probe

A

Smaller than curvy + linear ray

Goes to a point at the top

161
Q

Doppler effect =

A

There is a frequency shift if the target is moving.
(red blood cells, valves, vessel walls)

162
Q

Doppler effect: if frequency increases =

A

moving towards probe

163
Q

Doppler effect: if frequency decreases =

A

moving away from probe

164
Q

The higher the frequency shift (pitch) =

A

the faster something is moving

165
Q

MAXIMUM Doppler shift if

A

motion is parallel to the ultrasound beam

166
Q

ZERO Doppler shift if

A

motion is perpendicular (90 degrees)
to the ultrasound beam

167
Q

Continuous Wave Doppler:

A

one continuous beam

just sound no image

can be used to tell if something is moving

Point probe towards artery and sound is sent to speaker – tells us if there is blood movement (if there is a pulse)

168
Q

Doppler Waveform-Spectral Doppler

A

The velocity is plotted versus time.

The number of RBCs travelling at each velocity is assigned a grey level.

169
Q

the colour image consists of

A

many ultrasound beams
superimposed on the B mode image

170
Q

Colour Flow Mapping

A

pulses allow imaging

the colour box is made up of many beams, superimposed on the B mode image

each pixel shows mean Doppler frequency at that position
direction displayed
poor spatial resolution compared with B mode
subject to aliasing (incorrect pixel colours)

171
Q

Aliasing -

A

occurs when you get very high frequency shifts = very high velocities = cannot be displayed by colour

Indicates there is stenosis is present

Thus, just relying on B mode isnt good enough

172
Q

Neck arteries that supply the brain have…

A

a positive component throughout the cardiac cycle, in response to highly tuned feedback mechanisms, ensuring that there is constant, continuous flow to the brain

173
Q

The diastolic component of waveforms is sensitive to…

A

peripheral resistance - if distal arterioles dilate (hot foot, change in posture/gravity) then there may be a change in diastolic component in lower and upper limb arteries

disease can also change peripheral resistance

174
Q

Why are there so many probes?

A

Probes operate at a range of frequencies

C = curvilinear

L = linear

V = 3D/vector

Numbers = frequency range

175
Q

What probe to scan aorta?

A

deep structure

curvilinear 1-5MHz

176
Q

What probe to scan carotid?

A

superficial

Linear 12-18MHz

STP 1st year exams (4 decks)

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