The effects of reducing the thermal index for bone from 1.0 to 0.5 and 0.1 on common obstetric pulsed wave Doppler measurements in the second half of pregnancy.

摘要: Objective To test the hypothesis that clinically relevant vessels can be visualized and interrogated with Doppler recording during second half of pregnancy at an output energy below currently advocated limits without loss information. Design Observational cross-sectional study. Setting Tertiary fetal medicine center. Sample Based on a power calculation for equivalence studies, we recruited 65 pregnant women. Methods Ultrasound examination was performed 18, 24 or 36 weeks gestation. The umbilical artery, middle cerebral ductus venosus, both uterine arteries were identified using color Doppler, blood velocities measured pulsed wave thermal index bone (TIB) 1.0. This procedure repeated TIB values 0.5 0.1. depth noted. Main outcome measures Visualization by all levels any systematic changes increased variance recorded parameters decreasing level. Results All could their flow in participants levels. There no parameter when reducing level, despite insonation being significantly greater than early pregnancy. Conclusions Reducing ultrasound from 1.0 to 0.1 does not alter visualization measurements pregnancy. lower level recommended as starting point clinical examinations throughout