Abstract
Background: Patient safety is paramount in ultrasound procedures, particularly in obstetric ultrasounds involving both the mother and fetus. The thermal and mechanical indices (TI and MI) serve as crucial indicators of the acoustic output during ultrasound. Clinicians and specialists must know these indices and ensure they are within safe ranges. This study aimed to assess the parameters of acoustic output power employed in obstetric ultrasound (thermal and mechanical index).
Methodology: A cross-sectional observational study conducted at Maternity and Children's Hospital in Al-Madinah Al-Munawwarah, the data was collected from obstetric scanning of 411 pregnant females using a data collection sheet including gravida and women's age, gestational age, scan mode, scan time, and thermal and mechanical index (TI and MI) values.
Results: The study found that there were significant differences in safety indices measurement between different modes; in Pulsed Doppler, mean Thermal Index Bone (TIb) had the highest value (1.60±0.40), and the Mechanical Index (MI) was the lowest (0.68±0.33). There were insignificant differences in safety indices values in different modes in different trimesters. The thermal indices of soft tissue and bony structure (TIs and TIb) of brightness mode (B-mode) were constant in all trimesters, but the MI in the first trimester was lower than in the other trimesters.
Conclusion: This study concluded that the mean values of thermal indices used in B mode , M mode and Color Doppler lie within the Recommended limit of (BMUS) British Medical Ultrasound Society (below 0.7) except for Pulsed Doppler it was exceed 1.5. While for MI in different ultrasound modes except in pulsed Doppler the average values is higher than 0.7 which was recommended by (BMUS) British Medical Ultrasound Society and lower than 1.9 which was the maximum threshold approved by FDA (Food and drug Administration). The average scanning time is low (6.4 minute) reflect the safe use of ultrasound in obstetrics in this study.
