Ultrasound Flashcards
What are the basic ultrasound principles?
- Uses transmission of sound waves through tissue to produce an image
- Current is applied to the piezo-elements in the transducer
- Cuases the crystals to change shape and oscillate, producing an ultrasound wave
- returning sound waves are received at the transducer, causing compression of the crystals and thus an electric voltage
- The signal is then amplified, converted and dispalyed as a dot on the screen
What is Reflection?
A wave is reflected back to the transducer and called an echo
What is refraction?
The change in direction of a wave due to differing velocities of tissues
What is diffraction?
change in the direction of a wave through an opening or a barrier, allows sound waves to be detected
What is attenuation?
Loss of energy of a wave due to scatter or absorption
What is a linear array probe?
- Crystals in a line
- Rectangular image
- No near field artefact
- Large footprint
What is a curved probe?
- Crystals are in a curve
- Fan shaped image
- Near field artefact
- Smaller footprint
What is a phased array probe?
- Crystals in a line
- Fan shape- greater depth
- Steered electronically
- Smaller footprint
What is a high frequency ultrasound?
- Good axial resolution
- More rapid beam attenuation
- Poor penetration
What is axial resolution?
The ability to determine two points along the path of the beam
What is the definition of gain?
Changes the overall brightness of the image
What is time gain compensation?
- Echoes from deeper tissues are
weaker due to attenuation - TGC controls brightness at
different levels though the tissue
What is the focal zone?
- Area where the image is optimised by focusing the soundwave
- Most often shown by a triangular marker
- Keeps teh region interest in the focal zone
- Improves lateral resolution
What does reverbation cause?
Parrallel bright lines
What does mirror image cause?
occurs at the curved reflective surface
What is acoustic enhancement caused by?
Lack of attenuation
What is poor probe contact caused by?
Insufficient clipping or not enough gel
what is acoustic shadowing
If meet highly reflective interface get
complete reflection and distal shadow
what is edge shadowing
distal to lateral aspect cystic structure
what is slice thickness
part of the beam is wider than a cystic structure
When may you do an elective abdominal ultrasound?
- Any condition involving an abdominal organ
- Identifying and describing abdominal tumours
- Staging of neoplasia
- Intra-abdominal biopsy
- System-Specific Investigation, e.g repro tract
What is an emergency abdo ultrasound called?
POCUS scan
What are the benefits of an abdominal ultrasound?
- Non-invasive and safe
- Anaesthesia not required
- Good morph information
- Info from all major organs
- Real-time sampling of tissues is possible
- Relatively inexpensive
What are the disadvantages of an abdominal ultrasound?
- Limited functional information
- Diffuse disease is more difficult to detect
- Sampling is required to classify the disease
- Sedation often required
- Gas interferes with sound transmission
How would you prepare the patient?
- Withold food, ideally for 8 hours
- Extensive clipping
- Wash patient down to remove stray hairs
- Apply liberal amounts of coupling gel
- Sedation as required
- Lateral recumbancy
