title: Acoustic output measured by thermal and mechanical indices during fetal echocardiography at the time of the first trimester scan.
abstract: We measured acoustic output, expressed as the thermal index (TI) and mechanical index (MI), during fetal echocardiography at the time of the first trimester scan. TI and MI were retrieved from the saved displays during gray-mode, high-definition color flow Doppler and pulsed-wave Doppler (tricuspid flow) ultrasound examinations of the fetal heart and from the ductus venosus assessment. A total of 399 fetal cardiac examinations were evaluated. There was a significant increase in TI values from B-mode studies (0.07 ± 0.04 [mean ± SD]) to color flow mapping (0.2 ± 0.0) and pulsed-wave Doppler studies (0.36 ± 0.05). The TI from ductus venosus assessment (0.1 ± 0.01) was significantly lower than those from Doppler examinations of the heart. MI values from B-mode scans (0.65 ± 0.12) and color flow mapping (0.71 ± 0.11) were comparable, although different, and both values were higher than those from pulsed-wave Doppler tricuspid evaluation (0.39 ± 0.03). There were no differences in MI values from power Doppler assessment between the tricuspid flow and ductus venosus. Safety indices were remarkably stable and were largely constant, especially for color Doppler (TI), tricuspid flow (MI) and ductus venosus assessment (TI, MI). We acquired satisfactory Doppler images and/or signals at acoustic levels that were lower than the actual recommendations and never reached a TI of 0.5.
authors.affiliation: Department of Obstetrics and Gynecology, University of Medicine and Pharmacy "Gr. T. Popa", Iasi, Romania; "Cuza Voda" Obstetrics & Gynecology Hospital, Iasi, Romania. Electronic address: dragos.nemescu@umfiasi.ro.
authors.forename: Dragos
authors.initials: D
authors.lastname: Nemescu
authors.affiliation: "Cuza Voda" Obstetrics & Gynecology Hospital, Iasi, Romania.
authors.forename: Anca
authors.initials: A
authors.lastname: Berescu
mesh_terms: D065638:Absorption, Radiation; D000293:Adolescent; D000328:Adult; D001831:Body Temperature / Q000502:physiology* / Q000528:radiation effects; D004452:Echocardiography / Q000379:methods*; D055119:Elastic Modulus / Q000502:physiology / Q000528:radiation effects; D005260:Female; D005318:Fetal Heart / Q000000981:diagnostic imaging* / Q000502:physiology* / Q000528:radiation effects; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000502:physiology* / Q000528:radiation effects; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods; D013016:Sound; D013314:Stress, Mechanical; D016216:Ultrasonography, Prenatal / Q000379:methods*; D055815:Young Adult
keywords: Doppler ultrasonography; Fetal echocardiography; First trimester; Mechanical index; Output energy; Safety; Thermal index