Introductory Biomedical Imaging

Ultrasound Imaging Simulations

Ultrasound imaging is a medical analog of sound navigation and ranging (SONAR). Images are generated by directing a pulse of high-frequency (ultrasonic) sound into the body and detecting echoes that reflect or scatter from body interfaces and structures. The “echo time” between pulse creation and pulse detection is used to calculate object position. The echo amplitude is used to create image contrast, with strong echoes appearing white, weaker echoes as various shades of gray, and “absent” echoes as black. Doppler ultrasound further uses shifts in pulse frequency to measure object motion, such as blood flow. Doppler images are often color encoded and superimposed on grayscale structural ultrasound images. Ultrasound is extremely safe, relatively inexpensive, portable, and capable of creating excellent real-time images of soft tissues and organs. However, ultrasound is not well-suited to the study of air-filled cavities or structures encased in bone, like the brain. Premier applications include fetal imaging and Doppler ultrasound assessments of blood flow and heart valve movement.

The following simulations explore how ultrasound pulses are generated and detected, how pulse characteristics are used to create images, the factors that determine image quality (as quantified by resolution and contrast), and specialty imaging modes, including those used to monitor the eye, the heart, and blood flow. The simulations are listed in the recommended order of performance. Each simulation includes a home page from which the simulation can be run, together with links to simulation-specific Information, Background, and Activity documents.