What is the average attenuation of ultrasound in dB/cm for each megahertz of frequency?

• A. 1
• B. 0.7
• C. 0.33
• D. 0.25

Answer: (B)

The average attenuation of ultrasound in biological tissues is typically around 0.5 to 1.0 dB/cm/MHz, which indicates that as the frequency of the ultrasound increases, the attenuation also increases. This phenomenon occurs because higher frequency sound waves carry more energy and are more readily absorbed by tissues.

Choosing the value of 0.7 dB/cm/MHz aligns well with this average and is a commonly cited figure in the context of diagnostic ultrasound. This average value reflects the relationship between frequency and attenuation, providing a useful rule of thumb for estimating how much the ultrasound signal will diminish as it passes through tissues.

The other values presented do not accurately represent the typical attenuation rates for ultrasound in medical applications, as they are either too low or do not match the standard averages used in practice. Hence, selecting 0.7 dB/cm/MHz as the average attenuation for each megahertz of frequency is consistent with established understanding in the field.