A minor nit: at 17:22 you said that bone is highly attenuating and creates a shadow. It might be highly attenuating but the reason why the shadow occurs is that bone has a higher impedance (rho c product) than the neighboring tissue, so strong reflections occur and there is very little penetration. At high frequencies, like those used in sonography, there is also very little diffraction into the shadow zone. For those two reasons a shadow is created. Very highly attenuating tissue could, in theory, cause the same effect but it would occur gradually. Bone causes an abrupt reflection, and therefore an equally abrupt shadow. Thank you for the video!
