On a recent Wednesday night the crowd spilled out the door at San Francisco's Axis cafe, where the draw wasn't a hot band or a talented bartender, but a lecture. On physics.

Through structuring an ellipse being similar with target window's inscribes ellipse, it use major axis and minor axis to identify band.

A thin membrane as an echogenic band stretching across the left atrium could be identified with echocardiography on the parasternal and apical long axis views;