Assessing Acoustic Safety in Prenatal Ultrasound: A Comparative Study of Doppler and B-Mode Examinations

The widespread use of ultrasound in prenatal care raises concerns about fetal safety due to acoustic exposure. This study compared the thermal index (TI), mechanical index (MI), and scan duration between Doppler and B-mode examinations, while identifying the clinical indications for the use of Doppler.

A cross-sectional study was conducted on 264 pregnancy ultrasound examinations performed at one educational hospital and two private clinics. Certified radiologists and gynecologists performed all scans. Data were collected using a structured checklist. Scan modality, gestational age, TI, MI, scan duration, and clinical indications were recorded. Convenience sampling was used. Statistical analysis was performed using SPSS version 26, with significance set at p < 0.05.

Doppler scans comprised 23.5% of all examinations and were primarily indicated for intrauterine growth restriction (IUGR) and maternal hypertension. TI values were significantly higher in Doppler scans, while MI values exceeded the recommended threshold (0.4) across both modalities, especially in B-mode scans. Scan durations were longer for B-mode during later gestational weeks. No significant differences in safety indices were observed across imaging centers or ultrasound systems.

Although TI values remained within recommended safety ranges, persistently elevated MI values emphasize the need for vigilance. Doppler should not be routinely restricted but reserved for clinically justified cases. Sonographers should actively monitor TI and MI values during scans and minimize exposure time, adjusting scan duration according to gestational age and modality to ensure fetal safety.