Ultrasound Flashcards
What are ultrasounds?
Sound waves with frequencies higher than the human audible range
What is the upper limit for ultrasounds considered?
Upper limit is considered to be approximately 20kHz
How many functions does the ultrasound probe have and what are they?
• The ultrasound probe has 2 main functions:
a. Emit a sound wave
b. Receive the echoes from the original wave
What happens whenever an ultrasound wave passes through a tissue boundary?
• Whenever the ultrasound wave passes through a tissue boundary it can be reflected or will pass through and continue propagating
What will reflect more of the sound wave?
Adjacent tissues with varying densities will reflect more of the sound wave
What is some of the ultrasound beam lost to?
Some of the beam is lost to heat energy
Basics of an ultrasound
• Greyscale image
○ Colour can be added later
○ Bright white: bone
§ Bone reflects beam back
• Black: fluid
○ Nothing in the area is reflecting back
○ i.e. blood/amniotic fluid
• Everything in between is grey
○ Brightness of grey depends on density
• Top of an ultrasound image relates to where the hand is
○ Bottom of the image is deeper in
○ Sides of the image are dependent on which way the transducer has been held
-The image can be flipped if the wrist is rotated 180 degrees
Why do we use ultrasounds?
• No radiation
○ Needs to be used carefully in pregnant women as heat is produced
○ If used too often in pregnancy, heat can damage cells
○ Kept as low as reasonabaly achievable
• Widely accessible
• No documented side effects in humans
• Usually non invasive
• Well tolerated
• Results can often be available immediately
○ Bedside
• Real time imaging
-Can move patient around and see effects
Why not ultrasound?
• Training is more resource intensive for departments compared to other modalities
• Ultrasound image quality is dependent on patient habitus
○ Higher frequency = better resolution image but can only travel peripheral into the body
○ Lower frequency = deeper penetration
§ Lose details the deeper you go
• Effectiveness and accuracy are highly operator dependent
What are the variables involved in the choice of transducers?
○ Choice over sector width, scan depth (resolution), patient habitus, field of view
What screening is high frequency for?
• High frequency for more peripheral screening
How can we take images of blood vessels?
• Intravascular probe can be passed through catheter and take image of blood vessels
What are all women in the UK offered during pregnancy(12/20 weeks in)?
• All women in the UK are offered ultrasound sreening during pregnancy (12/20 weeks)
How long is the fetus between 11+2wks-14wks of pregnancy?
• Fetus is approximately 45-84mm in length (11+2wks – 14wks)
What does obstetric ultrasound detect?
○ Viability
○ Number of fetus’
○ Gross anatomy
§ Start to see larger pathology
§ Anencephaly – cranium hasn’t formed, brain is exposed
§ Omphalocele – mid-gut herniation
□ Mid abdominal wall hasn’t formed properly so contents of abdomen is outside of body
○ Detectable major abnormalities
§ Blighted ovum – miscarriage/ phantom pregnancy
○ Morphology of ovaries
Accurate gestational age of the fetus
What is down syndrome caused by?
Caused by change in one of the genes in egg before fertilization
What is the frequency of down syndrome in births?
• Frequency: 3/2000 births
What does fetal nuchal translucency screening use and to measure what?
Fetal nuchal translucency (NT) screening uses ultrasound to measure the size of the nuchal pad at the nape of the fetal neck
What increases the risk of down syndrome?
○ Increased thickness of sac of fluid at back of neck = increased risk
When should screening for downsydnrome be performed?
○ Should be performed between 11 weeks and 13 weeks + 6 days
What is image detail like in the 20 week scan and why is this the best time?
Finer details/pathologies as fetus is bigger
-Best time to do this because bigger than this and the baby is squashed so details are hidden
What can you see in 20 week scan?
Can see placenta and where it sits so it doesn’t cover baby’s exit
What abnormalities does a 20 week scan identify?
Identify abnormalities which:
- May indicate the baby has a life-limiting condition
- May benefit from antenatal treatment
- May require early intervention following delivery
What are the other standard aims of a 20 week scan?
Other standard aims:
- Placenta localisation
- Fetal Biometry
- Fibroid Monitoring
- Liquor Assessment
What does a Doppler ultrasound give information about and why is it able to do so?
Gives information about blood flow because it is in color
What is the shape of the cerebellum in spina bifida?
Cerebellum is in a banana shape because spina bifida is pulling down on the brain
What happens in achondroplasia?
- Bowing of long bones
- Shortening of limbs
What is achondroplasia a common form of?
Most common form of dwarfism
What surrounds long bones in achondroplasia?
Thickened soft tissue surrounding the long bones
What scans can we use to diagnose this?
3D ultrasound
How do we measure the distance of the placenta from the cervix and what is it done to ensure?
Measure the distance from lowest edge of placenta to the internal OS of cervix
-Need to ensure placenta is not covering exit
What is required if placenta is within 2.5 of the cervix?
If placenta is within 2.5cm of the cervix then future scans are required
What happens if placenta does not raise higher closer to due date?
If placenta does not raise higher closer to due date a c-section may be required
What is club foot/Talipes?
Internal rotation of the foot
What is the chances of a baby having club foot/talipes if one parent had a condition?
If one parent had the condition as a baby their own baby would have a 1 in 30 chance of also having talipes
What placental issues can arise?
- Oligohydramnios
- Polyhydramnious
When is heartbeat detected in fetus?
Can detect heartbeat at 5 weeks
What is the fetal pole detected as an area of?
The fetal pole is detected as an area of thickening along the periphery of a yolk sac
What is ectopic pregnancy?
When an egg implants outside of the uterine cavity it is know as an ectopic pregnancy
What are the symptoms of ectopic pregnancy?
-Associated with severe pain and also bleeding
What can ectopic pregnancy be caused by?
Can be caused by tubal damage
What is multiple pregnancy usually caused by?
Multiple pregnancy usually caused by delays in the fertilized egg reaching the womb before implanting
What can mothers with multiple pregnancy do?
Selective reductions
-People choose to terminate 1 or 2 fetus’ to give others a better chance of survival
Why is 3D/4D scanning useful ?
Useful for showing parents as they’re able to visualise
3D vs 4D scanning
3D: still image
4D: 3D moving image
What happens in amniocentisis?
Needle inserted into amniotic fluid to take sample from baby
What is the risk of miscarriage in amniocentesis?
1:3
What is follicle tracking used in conjunction with and to determine what?
Often used in conjunction with IVF treatments to determine the optimal time to extract eggs for fertilisation
What do fibroids consist of?
Consist of fibrous muscular tissue that has overgrown
What do fibroid eventually grow until?
Many eventually grow until the blood supply they receive can no longer support further growth
What are uterine polyps?
Growths from the inner wall of the womb which extend throughout the cavity and into the cervix and vagina
What can other malignant masses around polyps do?
Often malignant masses can exacerbate growth of vascular networks
What can tell us whether the poly is benign or mallignant?
Doppler can tell us where this extra vasculature Is so can tell us whetehr malignant or benign
What are the 3 features of PCOS?
- Irregular Periods – you don’t regularly release eggs
- Excess Androgens – (‘male hormones’ which may cause symptoms such as excessive hair)
- Polycystic Ovaries – ovaries become enlarged and contain additional fluid filled sacs (follicles which surround the eggs)
- A patient must exhibit 2 of these symptoms to be diagnosed with PCOS
What can aortic screening allow?
Can check abdominal aorta for aneurysm
Sizes of abdominal aorta and response
- If diameter is >3cm = risk
- If diameter >5cm = surgery needed
Where are aortic abdominal aneurysms monitored in?
AAAs are monitored in specialised clinics surgery
When is the section of abdominal aorta defined as aneurysmal?
Section of abdominal aorta is defined as aneurysmal when reaching 3cm in AP diameter
What method is used to treat an abdominal aortic anuerysm?
EVAR-Endo vascular aortic repair
What can fibrosis cause to the liver?
Fibrosis can decrease liver function
What are gallstones usually caused by?
Usually caused by an imbalance in the chemical make up within the bile
What is sonographic murphys sign?
If press probe down on gallbladder and results in pain = gallstone indication
How will gallstones look on an ultrasound?
Stones are denser so will reflect more ultrasound beam = bright white on ultrasound
What can bright white on ultrasounds be instead of gallstones and how do we differentiate between the 2?
Could a be polyp but polyps are attached are stones are free-moving
-In this case, ask patient to move and as stones move, if it moves = stone, if unmoved = polyp
What is testicular mass usually?
Testicular mass usually malignant
What happens to testicle if masses present?
Testicle is removed without any additional scanning
What is testicle surrounded by?
Testicle surrounded by fluid
What is hydrocele and what happens to testicular size?
Hydrocele is swelling that occurs around the testes due to build up of fluid and causes testicular size to increase
What can we demonstrate using colour flow doppler?
Using colour flow doppler we can demonstrate that the femoral vein is completely occluded by the lack of colour in this region
What does ultrasound of MSK allow us to see?
Allows us to see function whilst patient is moving
What is POCUS?
Point of care ultrasound
What is FAST?
FAST is an ultrasound scan protocol undertaken at the time of presentation of a trauma patient
What can ultrasounds detect in trauma cases?And compare values to x-ray
Ultrasound can detect as little as 20ml of free fluid, compared to 200ml required with plain x-ray
