Radiology Forums

Guest

1- Why is it difficult to do ultrasound of skull and lungs?

2- Why we use gel between skin and transducer?

3- Why we ask pregnant female patient to take a lot of water before ultrasound examination of uterus?

I think it is basic questions for you and I hope I can get the answers quickly.

ashley · Guest

Well, I can answer two of your questions. From what I understand, the gel is so that the image will go "through" the skin instead of reflecting back. And, pregnant women need to drink water because that is what the waves go through. I hope that little bit helps.

sonographer · Guest

The answers to your questions are simple.

We can not do sonograms on the skull because the speed that the soundwaves travel through bone and air. Propagation velocities of bone are much faster meaning that the sound waves, along with the stiffness of the acoustic interface do not allow us to image this. This also applies to aerated lung in the sense that the speed at which the soundwaves travel through it and the acoustic impedence of the interface is not optimal for imaging.
For your second question... we use gel to act as a "medium" between the soundwaves from the transducer through the skin. IF gel was not being used, we would not be able to image anything.
For your third question The speed at which the sound waves travel through fluid creates a "window" for the sonographer to visualize any underlying structure. Fluid creates "through transmission". In addition the full bladder also allows anteverted uterus to extend or lay back to visualize the full body of the uterus and push any bowel out of the way.

kalle1212 · Joined: 21 Aug 2006 Posts: 4 Location: Hudson Valley, NY

Very well said!