Ultrasound Basics

Learning Objectives

- Explain Basic Ultrasound Principles
- Learn how to Pick the Correct Ultrasound Probe
- Understand Ultrasound Terminology
- Understand Doppler Modes

Key Points

- US Imaging Terms:
  - Hyperechoic - Bright/White (ex. bone/air/gallstones)
  - Hypoechoic - Darker/Grey (ex. soft tissue)
  - Anechoic - Black (ex. fluid)
- Transducer Selection:
  - Linear array (“vascular” probe) - high resolution, low penetration (depth)
  - Phased array (“cardiac” probe) - low resolution, high penetration (depth)

Introduction to Basic Ultrasound Principles

Ultrasound (US) uses ultrasonic waves outwards and captures the “reflected” waves to recreate real life images onto a 2D screen through the “Piezoelectric effect.”
Based on the density (impedance) of the tissue/material, the image becomes anechoic (black), hyperechoic (darker/grey), or hyperechoic (bright/white) because of how fast the reflected wave comes back.
Generally, fluid is anechoic, soft tissue is hypoechoic, and bone/air/pericardium/gallstones are hyperechoic.

*both air and bone has very low/high density, which causes the wave to come back very quickly (without absorbance), thus making both look hyperechoic

Anechoic bladder

Hyperechoic pleural line

Hypoechoic liver

Picking the Correct Ultrasound Probe

Ultrasound Terminology

Pressure: increase force on probe to skin

Sliding: move probe along skin scanning an area.

Fanning/Tilting: change angle of probe so no longer perpendicular

Rotating: turn probe around midline

Rocking: change direction of US beam by altering angle of probe left to right

Basic Doppler Modes

B-mode (brightness mode)

Most commonly used image modality, usually on B-mode by default.

M-mode (motion mode)

Time motion display wave along a chosen ultrasound line plotted over time.

Images / information from: https://fusic-sy.co.uk/education/ultrasound-physics/ and https://www.pocus101.com/basic-principles-of-ultrasound-physics-and-artifacts-made-easy/.

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