3D/4D sonography – any safety problem

Abstract

Gray-scale image data are processed in 3D ultrasound by repeated scans of multiple planes within a few seconds to achieve one surface rendering image and three perpendicular plane images. The 4D image is achieved by repeating 3D images in short intervals, i.e. 3D and 4D ultrasound are based on simple B-mode images. During 3D/4D acquisition, a fetus in utero is exposed by ultrasound beam for only a few seconds, and it is as short as real-time B-mode scanning. Therefore, simple 3D imaging is as safe as a simple B-mode scan. The 4D ultrasound is also as safe as a simple B-mode scan, but the ultrasound exposure should be shorter than 30 min. The thermal index (TI) and mechanical index (MI) should both be lower than 1.0, and the ultrasound study is regulated by the Doppler ultrasound if it is combined with simple 3D or 4D ultrasound. Recently, some articles have reported the functional changes of animal fetal brain neuronal cells and liver cell apoptosis with Doppler ultrasound. We discuss cell apoptosis by ultrasound in this report. Diagnostic ultrasound safety is achieved by controlling the output pulse and continuous ultrasound waves using thermal and mechanical indices, which should be <1.0 in abdominal and transvaginal scan, pulsed Doppler, as well as 3D and 4D ultrasound. The lowest spatial peak temporal average (SPTA) intensity of the ultrasound to suppress cultured cell growth is 240 mW/cm2, below which no ultrasound effect has been reported. An ultrasound user must be trained to recognize the ultrasound bioeffects; thermal and mechanical indices, and how to reduce these when they are higher than 1.0 on the monitor display; and guide the proper use of the ultrasound under the ALARA principle, because the user is responsible for ensuring ultrasound safety.

ECCO-ESGAR Guideline for Diagnostic Assessment in IBD Part 1: Initial diagnosis, monitoring of known IBD, detection of complications

“…427 Ultrasound examination should be performed according to the 'as low as reasonably achievable' principle, 430 accounting for exposure time related to the thermal index generated during the procedure [keeping this value <1]. 431,432 433 Another retrospective study of 751 neonates exposed to 1.5T MRI in utero, compared with 10 042 unexposed neonates, found no difference between groups regarding birthweight or incidence of hearing impairment or deafness. 434 Specific data on MRI in pregnant women with IBD are limited.…”

Sonographic Evaluation of Fetal Cardiac Anatomy in the Late First Trimester

“…Therefore, exposure should be limited. 26 The mechanical index (MI) measures the potential that an ultrasound will create inertial cavitation. Cavitation is not possible in utero because of the absence of a gas-liquid interface.…”

Study protocol for a prospective cohort study to investigate Hemodynamic Adaptation to Pregnancy and Placenta-related Outcome: the HAPPO study

“…With respect to the risks of performing ultrasound examinations in the first trimester using 3D power Doppler, recommendations as set by the International Society of Ultrasound in Obstetrics and Gynaecology (ISUOG) are followed for the purpose of this study (ie, thermal index ≤1.0, mechanical index <1.9 and total exposure time <10 min). Transvaginal scanning time (preconception and first trimester) and transabdominal scanning time (second and third trimester) will be kept as short as possible according to the as low as reasonably achievable (ALARA) principles 47 48…”