Ultrasonography

Question 1

What is ultrasound?

Answer 1

Sound waves with the frequency that are higher than the human audible range

Between 20Hz and 20kHz is the audible range

The sound waves don’t travel far

Question 2

What is the pulse echo principle?

Answer 2

The ultrasound probe has 2 main functions

• emit a sound wave
• receive the echoes from the original wave

the ultrasound wave passes through a tissue boundary it can be reflected back or can pass through

• when the wave is reflected back it tells us what we want to see - the dots show the depth and the intensity of sound
• they represent the position of something

Adjacent tissues with varying densities will reflect more of the sound wave
Whereas adjacent tissues with similar densities will reflect less

Question 3

What is the link between amplitude and the reflection strength?

Answer 3

High amplitude = strong reflections
dense structures - bone - the ultrasound will return back strongly - a white image

Low amplitude - poor reflections/no reflections
ultrasound transmits through fluid therefore dark/black image is produced

Question 4

What are the clinical applications of ultrasound?

Answer 4

• Abdominal
• Urinary
• Trauma
• Testicular
• Breat
• Head/Neck
• Vascular
• Cardiology
• MSK
• Lunhs
• Obseterics
• Gynaecology

Question 5

Why do we use ultrasound?

Answer 5

No radiation
- ionising radiation is not used therefore no damage is caused to the patient

Non-Invasive
- sometimes need to do vaginal scans to get higher resolution imaging - as there is less soft tissue between the probe face and the organ

Real time

• moving pictures - can see things move therefore can track certain movements
• gall stones trickling down and fetus moving

Widely accesible

Results can be available immediately

No documented side effects in humans

Well tolerated

Question 6

Why would we not use ultrasound?

Answer 6

Training is more resource intensive
- only certain members of staff/departments can use the equipments as they are trained in it

Ultrasound image quality is highly dependent on patient habitus

• resolution may not be clear - limited in certain patients
• high BMI means there is more soft tissue between the probe and the organ therefore more information gets attenuated and you cant get high resolution images

Effectiveness and accuracy are highly operator dependent

No known side effects
- it is a new form of scanning therefore the side effects are unknown

Question 7

Why do we have a selection of transducers?

Answer 7

Increased choice of technical variables allows for the imaging to be more specific 
Can choose over:
- sector width 
- scan depth - resolution 
- patient habitus 
- field of view

Question 8

What is obstetric ultrasound?

Answer 8

It is a major advantage to use an ultrasound scan compared to an X-ray as there is no radiation involved and therefore less damage to the foetus

all woman are offered ultrasounds at 12/20 weeks

the scan is used to see if there is a problem with the foetus and to predict the due date

12 week scan - confirm there is a baby, the heart is beating, the gestation period, the number of babies
- can base the other pregnancy tests e.g blood tests around the findings from week 12

Question 9

What happens at the 12 week scan?

Answer 9

Fetus is approximately 45-84mm in length - around 14 weeks