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Y3 MOD > Diagnostic ultrasound > Flashcards

Diagnostic ultrasound Flashcards

1
Q

How are ultrasound waves generated

A

Piezoelectric material – vibrates when a current is put across it, when it vibrates it generates a current as well
Wavelength (frequency) – determines how well it penetrates tissue

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2
Q

How are ultrasound waves propagated?

A
  • The wave propagates through the tissue and is reflected by the tissue
  • The amount of reflection depends on the echo-density of the tissue
  • The time from when the pulse starts to when the reflection comes back is a measure of the distance from the probe and the object reflecting it
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3
Q

Which tissue completely reflects the wave?

A

Bone

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4
Q

How can artefacts occur?

A
  • Reflection/reverberation
  • Refraction
  • Acoustic enhancement
  • Poor resolution
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5
Q

What is the relationship between wave frequency and resolution?

What is the relationship between penetration and frequency?

A

shorter frequency = higher resolution

more detail can be seen in closer structures to the probe - less penetration = higher resolution = shorter frequency

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6
Q

When is the earliest that you can pd a cow?

A

25 days

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7
Q

Why is it beneficial to pd earlier?

Why is it beneficial to pd later?

A

Identify non-pregnant animals

Fetal loss over time - “accuracy”

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8
Q

A 37 day old foetus is how big?

A

1cm

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9
Q

When should you dry off a pregnant cow?

A

60 days before birth

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10
Q

How does the fluid appear on an ultrasound in a cow in oestrus compared to a pregnant cow?

A
  • oestrus - star shaped fluid

- pregnant - circular fluid

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11
Q

what other things can be observed on ultrasound that indicate a cow may be pregnant?

A

CL present on the ovary that last ovulated - foetus is most likely to be in this uterine horn (60%+ time in R horn!!)
CL may:
- be fluid filled - if >35mm, luteal cyst?
- or solid
- appear to have a line through

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12
Q

Most of the time, cattle foetuses stay in the same horn as the CL - how do horses differ?

A

Horse foetuses migrate in the uterus so could be in either horn

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13
Q

What factors do we assess when determining if a cow is pregnant?

A
  • position
  • fluid
  • CL
  • foetus
  • heartbeat
  • placentomes
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14
Q

How does amniotic fluid appear on an ultrasound?

A

Cloudy

- Foetus discharges urate into it

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15
Q

How does Allantochorionic fluid appear on an ultrasound?

A

Black

- if it is cloudy it could be a sign of an infection

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16
Q

Can twins be detected on ultrasound?

A

yes, at any stage but easiest once floated off wall but small enough to be on a single image (30-40d)
counting CLs is usually best way to detect twins

17
Q

What % of twins are bilateral and unilateral

A

40% of twins are bilateral and 60% unilateral

18
Q

Are twin pregnancies most likely to be lost if they are unilateral or bilateral?

A

8% of bilateral

35% of unilateral

19
Q

how can a foetus be aged on ultrasound?

A
  • mid-sagittal section for crown-rump length
  • horizontal section for biparietal distance (across the head)
  • transverse section for trunk diameter
20
Q

Why may some people want foetal sexing to be carried out?

A
  • Sufficient male or female offspring for progeny testing
  • Keep dams bearing heifer replacements
  • Keep dams bearing bulls attracting subsidy
21
Q

What is progeny testing?

A

Progeny Testing refers to evaluation of bulls on the basis of their daughter’s performance

22
Q

How is foetal sexing done?

A

Genital tubercle migrates so that at about day 56 it is:

  • Just behind the umbilicus in males
  • Between the back of the hind legs and the tail in the female

Teats and scrotum can be identified from 70 to 120 days

23
Q

uterine abnormalities:

  1. what could cloudy fluid in the uterus indicate?
  2. what could a hard mass with bones indicate?
A
  1. cloudy fluid - mucometra, endometritis, pyometra

2. hard mass - mummified foetus

24
Q

Name an ovarian abnormality

A

Granulosa cell tumour

25
Q

Describe some features of an ultrasound scanning routine up to finding an ovary

A
  • logical and systematic
  • clear decision making framework
  • evacuate faeces from rectum
  • insert protected and lubricated hand into rectum
  • use fingers to identify cervix
  • either move sideways from the cervix or follow the right horn round to identify the right ovary
26
Q

Describe the scanning routine once the ovary has been identified

A
  • Obtain an image of the ovary and see if it has a CL
  • Scan horn towards uterine body - look for fluid, white line of amniotic vesicle and eventually fetus
  • If no fetus repeat process on left ovary and horn
  • Scan fetus from trunk towards head for heartbeat
  • Estimate age, sex
27
Q

What should you do if there is fluid present but no foetus?

A
  • recheck both horns
  • is uterus over pelvic brim?
  • put probe over brim – placentomes? diameter?
  • is fluid cloudy? flecky?
  • any masses?

Y3 MOD (23 decks)

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