Basics of US (under construction)
Ultrasound transducer sends sound waves through the body.
Sound waves are reflected differently by various types of tissue, and sent back to transducer where signal is transformed into visible image.
Sound waves do not travel through and are reflected by air or bone (calcium), resulting in shadowing behind these structures.
Sound waves travel through fluid, which thus appears black or anechoic on US.
Soft tissue appears the same brightness as surrounding tissue or isoechoic.
Transvaginal sonography gives a more detailed evaluation of pelvic architecture using higher frequency transducers at closer proximity to pelvic structures.
The Doppler Ultrasound indicates flow of fluid, which includes but is not specific to blood flow.