17-11-21 - Clinical Application of Ultrasound Flashcards
Learning outcomes
- Understand the Benefits vs Risks of Ultrasound.
- Understand the role of ultrasound in diagnosis.
- Understand the benefits and limitations of point of care ultrasound (POCUS)
What is Lithotripsy?
What then happens to these particles?
- Lithotripsy is when stones present in the urinary system are crushed into small sand like particles by the vibratory impulses generated by biphasic ultrasound shock waves
- These small particles are then excreted in the urine
What is thermal index (TI)?
What is mechanical index (MI)?
What are measures that can be taken to minimise the risk of ultrasound?
What principle does this refer to?
- Thermal index (TI) provides an onscreen indication of the relative potential for a tissue temperature rise during ultrasound
- Mechanical index (MI) provides an onscreen indication of the relative potential for ultrasound to induce an adverse bio effect by a non-thermal mechanism, such as cavitation
- Perform DUS only when medically indicated, using the lowest acoustic output compatible with diagnosis, and for the shortest exposure possible
- This refers to the ALARA principle (As Low As Reasonable Achievable)
What are the 10 British Medical Ultrasound Society guidelines for the safe use of diagnostic ultrasound equipment?
- Perform a scan only when indicated.
- Know the machine you use.
- Keep the examination as short as possible.
- Always start a scan at the lowest possible output (default) and increase only if necessary.
- Follow the ALARA principle.
- Use receiver gain to optimize image.
- Keep track of the TI and MI values on the screen.
- Keep TI below 1.
- Keep MI below 1 (although some recommend 0.5).
- Be extremely cautious when using Doppler in the first trimester
What does ALARA stand for?
What does it mean?
- ALARA is an acronym for As Low As Reasonable Achievable
- It means making every reasonable effort to maintain exposures to ionizing radiation as far below the dose limits as practical
What is the definition of Point-of-care Ultrasound (POCUS)?
- Point of care ultrasound (POCUS) is defined as a goal-directed bedside ultrasound examination performed by a healthcare provider
- This is in order to answer a specific diagnostic question or to guide performance of an invasive procedure
What is the angle of incidence in ultrasound?
What happens if the angle of incidence is perpendicular to the structure?
What happens if the angle of incidence is more parallel to the structure?
- Th angle of incidence in ultrasound is the angle at which US waves encounter the surface of the structure, which affects the way it is presented on the screen
- If the angle is perpendicular, or close to perpendicular (90 degrees), more US waves will be reflected back to the transducer, and fewer will be scattered away as a result, resulting in better image quality
- If the US waves are more parallel to the surface of the object (more than 45 degree of incidence), the image will have less definition
What are 9 Uses of ultrasound?
1) Central venous Catheter Insertion
2) Infant hip dysplasia
3) Cranial ultrasound
4) Echocardiography
5) Assessment of limping child
6) Ultrasound guided joint aspiration
7) Ultrasound guided steroid injection
8) Ophthalmic US
9) Find needle aspiration using USS guidance for cytology (examination of single cell type)
Central venous catheter insertion
Infant hip dysplasia ultrasound
Cranial ultrasound
What is Echocardiography?
• Echocardiography is the use of standard US or Doppler US to image the heart and nearby blood vessels
Assessment of a child limping US
What is Power Doppler sensitive to? What is it good at detecting?
- Power Doppler is sensitive to low blood flow in small vessels
- It is good at detecting synovitis, which is a swelling of a synovial membrane (can be caused by types of arthritis and other diseases)
Ultrasound guided joint aspiration (removal of fluid around a joint using a needle/syringe)
Ultrasound guided steroid injection
What is important during ophthalmic Ultrasound?
• The eye is a very vulnerable organ, so MI, TI and duration of US need to be kept down
Fine needle aspiration using USS guidance for cytology (exam of single cell type)
What is cytology?
What do normal and malignant cell types look like?
• Cytology is the exam of a single cell type
What is Focuses Assessment with Sonography in Trauma (FAST)?
What is it normally used to identify?
- Fast is a limited ultrasound scan performed in the emergency department to assess patients admitted with blunt abdominal trauma
- It is normally undertaken by emergency physicians in order to identify the presence of free fluid, which may represent (internal bleeding in peritoneal cavity)
