Practical Physics Module Outline

1.1 Seeing with Sound

• Definition of ultrasound and sound wave properties.
• Internal components of an ultrasound transducer.
• The piezoelectric effect and energy conversion.
• Process of sound transmission, reception, and image generation.

1.2 256 Shades of Grey

• Interaction of sound with various tissue types.
• Mechanics of reflection, refraction, and scattering.
• Definitions of echogenicity (anechoic, hyperechoic, etc.).
• Relationship between acoustic impedance and the grayscale image.

1.3 Which Probe and Why?

• The inverse relationship between frequency and wavelength.
• Factors affecting axial and lateral resolution.
• Physical attributes of Linear, Curvilinear, and Phased Array probes.
• Function and parameters of factory presets.

1.4 Artifacts: Is My Image Lying to Me?

• The four sources of artifacts: acoustic, equipment, operator, and patient.
• Standard ultrasound machine assumptions (1540 m/s, straight-line travel).
• Introduction to the Hide, Help, Mimic, and Degrade classification system.

1.5 Artifacts that Hide Pathology

• Physics of “clean” vs. “dirty” shadowing.
• Posterior acoustic enhancement mechanics.
• Causes of reverberation, comet tail, and ring down artifacts.
• Identification and mitigation of edge refraction shadows.

1.6 Artifacts that Mimic Pathology

• Mechanism of mirror image artifacts at strong reflectors.
• Physics of anisotropy in tendons and nerves.
• Causes of secondary lobes (Side and Grating lobes).
• Strategies for verifying phantom structures in multiple planes.

1.7 Artifacts that Degrade Image Quality

• Impact of over-gain and under-gain (Pseudosludge vs. Pseudocyst).
• Identification of electrical interference and crystal dropout.
• Impact of patient habitus and loss of probe contact.
• Technical optimization using TGC and focal zones.

1.8 Artifacts that Help Diagnose

• Diagnostic utility of acoustic enhancement in identifying fluid.
• Using clean shadowing to confirm calculi or bone.
• Differentiating Comet Tail from Ring Down for lung and gallbladder pathology.
• Use of the “Positive Mirror Image” to rule out pleural fluid.

1.9 Ultrasound Modes Explained

• Mechanics of B-Mode (2D grayscale) and M-Mode (motion).
• Doppler physics: Colour, Power, and Spectral (PW/CW) modes.
• Temporal vs. spatial resolution trade-offs.
• Appropriate clinical selection for each imaging mode.

1.10 Keeping Your Patients Safe

• Thermal effects and the Thermal Index (TI).
• Non-thermal effects (cavitation) and the Mechanical Index (MI).
• Implementation of the ALARA principle.
• Safety guidelines for obstetric and vulnerable patient populations.