Ultrasound Physics + Echocardiography| 112 QUESTIONS| WITH COMPLETE SOLUTIONS

The human ear can perceive sounds up to _______, above which sounds are referred to as "ultrasound." a. 5 kHz b. 20 kHz c. 5 MHz d. 20 MHz correct answer: B: 20 kHz. Ultrasound frequencies in imaging are usually 3-12 MHz The piezoelectric effect refers to converting ____ energy into ____ energy. correct answer: Electrical energy into kinetic or mechanical energy. Which of the following is NOT a parameter to be considered when minimizing ultrasound-induced thermal injury? a. Haired/non-haired skin b. Exposure time c. Protein content of tissue d. Perfusion of tissue e. Emission modality (e.g. B-mode vs. pulsed-wave) f. Beam width g. Pulse repetition frequency h. Size of scanned area i. Focus depth j. Frequency correct answer: A. Protein content in tissue is directly related to absorption coefficient. The higher the absorption coefficient the greater the temperature increase in tissues during ultrasound (e.g. bone has the highest absorption coefficient and temperature rise). Deep focus and decreased frequency requires an increase in power which increases heating damage. T/F: Ultrasound-induced biologic effects may include endothelial damage with secondary thrombus formation and cellular injury via free radical production. correct answer: TRUE. Thrombus formation was one of the earliest demonstrations of its biologic effects How does the process of acoustic cavitation lead to tissue damage? What is a clinical example of the deleterious effects of cavitation? correct answer: The interaction of ultrasound with gas bubbles (e.g. lungs, intestines) causes rapid and potentially large changes in bubble size (cavitation). This may increase temperature and pressure within the bubble and cause mechanical stress on surrounding tissues, precipitate fluid microjet formation, and generate free radicals. Pulmonary hemorrhage is a well-studied example of cavitation - hemorrhage originates from microvasculature of the visceral pleura. Acoustic impedance = ___________ x __________ correct answer: Velocity/speed of ultrasound waves X density of tissue How does using a harmonics mode improve tissue contrast? correct answer: The transmitted pulse deforms as it travels through tissues from a perfect sinusoid to a sharper, sawtooth shape which causes a change in the reflected echoes. Using higher-order harmonic echoes instead of just listening for the fundamental echo (initial pulse wave) results in improved image contrast and reduced noise. Which of the following components comprise ultrasound contrast media: a. Nitrogen gas b. Helium gas