Ultrasound Flashcards
What are the pros of ultrasound?
- non-invasive
- performed on conscious patients
- differentiate soft tissue from fluid
- real time on moving image produced
- do not damage living cells.
What are the cons of ultrasound?
- unable to penetrate bone or air and so cannot be used to assess the skeletal system.
- interpretation of images requires skill and practice.
What is the ultrasound beam produced by?
a transducer probe.
What is inside the probe?
- special crystals = piezo-electric crystals..
What happens to the crystals during an ultrasound procedure?
The electrical current is applied and causes it to vibrate and alter their shape.
this is called the piezoelectric effect.
What happens when the probe is close to the body cavity?
when close contact with the skin, the vibrations are sent to the tissues in the form of sound waves.
what happens to the sound waves after close contact with skin?
They are reflected back and received by the transducer and causes the crystals to vibrate.
thus converting into an image.
What is acoustic impedance?
indicates how much sound pressure is generated by the vibration of molecules.
what is “high” acoustic impedance?
the sound waves are reflected back.
what is “low” acoustic impedance?
the sound waves penetrate the material without being absorbed.
What is anechoic?
when no echoes are reflected back to the transducer e.g. fluid
what is hyperechoic?
when lots of echo ar reflected back, e.g. bone, masses.
what is hypoechoic?
when small or low numbers of echoes are reflected back e.g. different tissue types, soft tissue.
what is acoustic enhancement?
- area is increased brightness underneath fluid resulting from the lack of impedance.
- when the sound wave pass through, fluid and increases echoes from underneath structure.
what are three types of transducers?
- sector
- linear
- curved
what is the sector transducer?
- a narrow fan image near the transducer.
- increase i width with deeper penetration.
-cons = poor near field resolution.
this is mostly used in practice.
what is linear transducer?
- sound waves that are produced parallel to each other.
- mainly used in large animals rectal examination.
- cons = artefacts are created when applied to a curved part of the body.
- it can create air gaps between skin and transducer.
what is curved transducer?
- compromised of the linear and sector scanner.
- density of the scan lines decreases with increasing distance from the transducer.
- can be difficult to use in curved regions of the body. e.g. spleen behind the left costal margin.
How do you maintain the equipment?
- equipment is expensive.
- probe must be cleaned after each patient with the recommended cleaner.
- DO NOT USE SURGICAL SPIRIT.
- avoid dropping the probe.
- must be stored in a padded case.
- any damages should be reported to a suitably qualified engineer.
There are four different modes, what are they?
- A Mode
- B Mode
- M Mode
- Doppler
What is A-Mode?
- Amplitude Mode
- graphic display rather than an image.
- purpose of measuring between tissue interfaces.
- e.g. foetal skull size to ass maturity.
- Not common in veterinary practice.
what is B-mode?
- brightness mode
- give us a 2D representation of cross sectional anatomy.
- each echo is given a grey scale value relating to strength of echo.
- most common in practice.
- used to diagnose pregnancy and view structure of the abdomen.
what is m-mode?
-motion
- how the position of tissue interfaces alter with time.
- produced in wavy lines.
- m-mode is used in cardiology to diplay the movement of the heart valves.
- this is recorded in shades of grey.
what is the doppler?
- used to detect movement.
- usually the flow of blood.
- but can be asses through:
1) direction of flow
2) speed of flow
3) flow pattern
4) vessel stenosis
how prepared does the patient need to be?
- patients fur is clipped and skin is cleaned.
(air/dirt/grease are poor conductors and will reduce the quality of the image). - skin cleaned with chlorhexidine.
- a special coupling gel is applied to the transducer and the patient.
- patient needs to be monitored throughout to ensure tolerance and to prevent grooming (conscious) and especially if sedated/anaesthetised.
What necessary position do small animals have to be in?
- Dorsal
- Lateral
- Soft bedding used, to prevent injury.
What four areas are ultrasound used?
- tendon and ligament injury.
- orthopaedics
- pregnancy scanning
- biopsy and FNA guidance.
