Anaesthesiology
The Physics of Medical Ultrasound
Built from Practical Ultrasound in Anesthesia
What’s inside
11 sections · 49 slides
Overview
- Topics covered
Sound waves and a short history
What sound is, and the milestones that turned it into medical imaging
- Properties of sound waves
- Milestones in medical ultrasound
- A-mode: amplitude plotted against depth
- B-mode: the greyscale image
Generating the ultrasound beam
Frequency, wavelength, and how a crystal turns electricity into sound
- Frequency and wavelength
- The piezoelectric effect
- Ultrasound image formation
- 1540 m/s
M-mode and the echo principle
Motion-mode imaging, how depth is calculated, and acoustic impedance
- M-mode (motion mode)
- M-mode of the inferior vena cava
- Calculating depth from echo time
- Acoustic impedance and reflection
- Acoustic coupling
- Acoustic Impedance
Doppler
How a moving target shifts frequency, and how colour shows flow direction
- The Doppler effect and Doppler shift
- The Doppler principle
- Doppler shift and flow direction
- Colour Doppler on a medical image
Attenuation, resolution, and depth
Where ultrasound energy goes, and the trade-off between detail and penetration
- Attenuation: energy lost in tissue
- Time gain compensation
- Contrast and spatial resolution
- Balancing resolution and penetration
- Spatial compound imaging
Probe manipulation and anisotropy
How to handle the probe, and why the angle of the beam matters
- Probe manipulation: PART
- Principles of Ultrasound Probe Manipulation
- Anisotropy
Elastography, harmonics, and artefacts
Measuring tissue stiffness, using harmonics, and why artefacts appear
- Elastography
- Harmonic imaging
- Defining an ultrasound artefact
- Assumptions behind the ultrasound image
- Commonly Encountered Artefacts
- Commonly Encountered Artefacts (continued)
Ultrasound probes
The common transducer types and which structure each one images
- Probes: crystal arrays
- Common Ultrasound Probes
Recent technology advances
Compound imaging, needle visualisation, tracking, and tip-mounted ultrasound
- Advances in image generation
- Needle visibility and its limits
- Echogenic needles
- Types of echogenic needle
- Laser-etched versus standard needle
- Electromagnetic and piezo needle tracking
- Micro-ultrasound at the needle tip
Therapeutic ultrasound
MR-guided focused ultrasound as treatment, and its risks
- MR-guided focused ultrasound
- Creating the thalamic lesion
- Key takeaways
- References
- References
- References
- Practical Ultrasound in Anesthesia for Critical Care and Pain Management