What is the peak intensity found across the sound beam?

• A. Spatial Peak
• B. Spatial Average
• C. Mechanical Index
• D. In Vivo

Answer: (A)

Inside an ultrasound beam, intensity isn’t the same everywhere. The highest value present anywhere within the beam’s cross-section is called the spatial peak intensity. It represents the maximum instantaneous power per unit area the beam delivers at any point. This is different from spatial average intensity, which is the mean intensity across the entire beam area and is typically lower. Mechanical Index is a separate safety parameter related to pressure and frequency, not the beam’s intensity distribution. In Vivo isn’t an intensity term at all; it refers to measurements made in living tissue. So the peak intensity found across the sound beam is the spatial peak intensity.