On the safety of elastography in fetal medicine: A preliminary study of hypoacusia

cc ep te d A rti cl e On the safety of elastography in fetal medicine: A preliminary study of hypoacusia 1Paloma Massó, 1Guillermo Rus, 2Francisca Molina 1University of Granada Structural Mechanics, University of Granada Politecnico de Fuentenueva Granada, Spain 2 San Cecilio University Hospital (HUSC) Maternal-Fetal Medicine Unit. Department of Obstetrics and Gynaecology, Granada, Spain Corresponding Author: Professor Guillermo Rus University of Granada Structural Mechanics University of Granada Politecnico de Fuentenueva Granada 18071 Spain T: +34 958240037 [email protected] Elastography is a promising technology to provide additional clinical information on the cervical effacement to that obtained from Bishop test and conventional cervicometry by ultrasounds. Among the different techniques, transient, or acoustic radiation force elastography (ARFE) is becoming the most common commercial elastography technique. However, the high intensity of thr beam that ARFE emits to generate the necessary concentrated burst of acoustic radiation [1] to induce a tractable shear oscillatory displacement (see Figure 1), has raised some concerns about its potential teratogenous effects during pregnancy. This letter is aimed at opening a debate to assess the safety of this type of elastography, and in particular to provide a preliminary screening of cochlear damage in exposed fetus. The employed energy input by ARFE has not been tested when designing the current standard safety criteria, that is, the mechanical index (MI) related to the formation of bubbles by cavitation, and thermal index (TI) related to temperature elevation. In particular, fetal exposure to general ultrasound is limited by the US Food and Drug Administration (FDA) to a maximum spatial peak temporal average intensity of 720 mW/cm2 and maximum mechanical index of 1.9 [2]. Both indices are time-averages that do not capture orders of magnitude higher mechanical energy peaks concentrated during a few microseconds per second of operation (depending on the multi-frame elastography interval). Therefore, the possible