What is the jelly stuff called that doctors put on pregnant stomach during a ultra sound?

The jelly-like substance used during ultrasound examinations is called ultrasound gel. It serves several important purposes:

1. Acoustic Coupling: Ultrasound waves require a medium to travel from the ultrasound transducer to the patient's body and back. Air pockets between the transducer and the skin create gaps that can hinder the passage of sound waves, resulting in poor image quality. Ultrasound gel eliminates these air pockets by providing a smooth interface between the transducer and the skin, allowing for efficient transmission of sound waves.

2. Impedance Matching: Acoustic impedance is a measure of the resistance that a material offers to the passage of sound waves. The human body and ultrasound transducers have different acoustic impedances, which can cause sound waves to reflect and scatter at the interface, leading to distorted images. Ultrasound gel has an acoustic impedance similar to that of human tissue, minimizing impedance mismatch and ensuring accurate transmission of sound waves.

3. Signal Enhancement: Ultrasound gel improves the quality of ultrasound images by enhancing the reflection and transmission of sound waves. It contains particles that scatter the sound waves, increasing the number of echoes received by the transducer. These increased echoes allow for clearer and more detailed visualization of internal structures.

4. Cooling Effect: During an ultrasound examination, the transducer generates heat. Applying ultrasound gel helps dissipate this heat, preventing discomfort to the patient and ensuring the longevity of the transducer.

Ultrasound gel is typically water-based, hypoallergenic, and bacteriostatic to minimize the risk of allergic reactions or bacterial contamination. It is applied directly to the patient's skin over the area of interest and wiped off after the examination.