According to AIUM bioeffects, there have been no confirmed bioeffects below intensities of what SPTA?

• A. 0.01
• B. 1
• C. 0.1
• D. 10

Answer: (C)

Understanding AIUM bioeffects involves how much energy the tissue experiences over time. The spatial-peak temporal-average intensity (SPTA) is the measure of heat delivered per unit area during the ultrasound exposure. Evidence gathered and summarized by AIUM indicates that there have been no confirmed bioeffects observed below an SPTA of 0.1 W/cm^2. This value represents the safety benchmark used in diagnostic imaging to indicate a level at which the literature has not shown confirmed adverse effects under typical exposure conditions. The other options fall outside this established threshold, either being lower or higher than 0.1 W/cm^2, but the guideline cited by AIUM centers on 0.1 as the boundary where no confirmed bioeffects have been demonstrated. Keep in mind that real-world safety also depends on factors like exposure duration, frequency, and other safety indices, but the 0.1 W/cm^2 figure is the key reference for this question.