Which intensity has the most significant relevance concerning tissue heating?

The intensity most relevant to tissue heating is the Spatial Peak Temporal Average intensity, often abbreviated as SPTA. SPTA represents the highest intensity of an ultrasound beam (spatial peak), averaged over time (temporal average). This measure takes into account both the peak strengths of the ultrasound pulse and the duty cycle, which is the proportion of time the ultrasound is actively transmitting versus the total time of the pulse cycle.

Tissue heating is primarily influenced by the intensity of ultrasound energy absorbed by the tissue, which relates closely to the SPTA measurement. Higher SPTA values indicate more significant energy delivery to the tissue, resulting in increased heating. Thus, it offers the most direct estimate of the potential thermal effects of ultrasound on biological tissues.

In contrast, other intensity measures like Spatial Peak Pulse Average (SPPA) and Spatial Peak Temporal Peak (SPTP) do not consider the time-averaged nature of energy delivery, which is crucial for understanding thermal effects. The SATA (Spatial Average Temporal Average) intensity, while relevant for evaluating overall exposure, does not reflect the peak intensity that is particularly critical for tissue heating assessments. Therefore, SPTA provides the most relevant metric for evaluating potential tissue heating in ultrasound applications.