The thermal dose index.

Objective: A new index is proposed to help sonographers easily assess the risk of an adverse thermal effect arising from a clinical examination. It is called the thermal dose index (TDI).

Methods: The TDI uses the familiar thermal index (TI) and the examination duration to compute a dimensionless index.

Results: The greater the TDI value, the greater the risk of a thermally induced adverse effect. If the TDI is 1 or less, there is no expectation of a thermally induced adverse effect.

Conclusions: Like the TI, the TDI would be a convenient index that is continually updated and displayed during an ultrasound examination. The TDI is a new estimate of thermal risk that takes into account the duration of an ultrasound examination.