Ultrasound Physics - Image Generation

Audience: Radiology Residents

Learning Objectives:
Describe the physics of ultrasound image generation
Explain how transducer frequency impacts image quality
Describe user controlled features that can impact image quality

Summary:
Mechanic energy transmitted as waves
Alternating compression and rarefaction
Waves are reflected, scattered, refracted, or absorbed
Reflected waves produce the image you want
Scatter, refraction, absorption decrease signal, increase noise and create artifacts

Strength of Reflection is base on tissue interfaces
The difference in acoustic impedance
Surface
Size
Orientation
High frequency probe – Low penetrance, high resolution
Low frequency probe – high penetrance, low resolution
Harmonics and compound imaging improve image quality and may reduce

References:
Hertzberg, Barbara S., and William D. Middleton. Ultrasound: the requisites. Elsevier Health Sciences, 2015.
Hangiandreou, Nicholas J. "AAPM/RSNA physics tutorial for residents: topics in US: B-mode US: basic concepts and new technology." Radiographics 23.4 (2003): 1019-1033.
Boote, Evan J. "AAPM/RSNA physics tutorial for residents: topics in US: Doppler US techniques: concepts of blood flow detection and flow dynamics." Radiographics 23.5 (2003): 1315-1327.