What is the proper method used to assess the size of the dead zone?
1) Trace the volume of the portion of the image that demonstrates reverberation at the top of the screen
2) Measure the width of the area of reverberation at the top of the screen
3) Trace the area of the portion of the image that demonstrates reverberation at the top of the screen
4) Measure from the top of the image to the depth that uniform tissue is identified