Understanding and interpreting your Transthoracic Echocardiogram.

I think that most of the aortic root measurements can be obtained using different "views". I understand the "Left para-sternal long axis view" best.

http://www.med.yale.edu/intmed/cardio/echo_atlas/contents/index.html
http://www.echopedia.org/wiki/Parasternal_long_axis
http://www.chfpatients.com/tests/echo.htm