Cardiology MCQ: Echo Basics

Doppler echocardiography is best done with the ultrasound beam:

A. Parallel to the direction of blood flow

B. Perpendicular to the direction of blood flow

C. At an angle of 45 degrees to the direction of blood flow

D. At an angle of 135 degrees to the direction of blood flow

Correct answer: A. Parallel to the direction of blood flow

While two dimensional imaging gives better view if the structure being imaged is perpendicular to the beam direction, Doppler estimates the velocity of moving red blood cells best when the direction of beam is parallel to the direction of blood flow. This can be stated as zero angle of insonation for optimal results. Slight angulations can be taken care of by angle correction algorithms in the machine. But if the angle is more than 20 degrees, high errors may give unphysiological values with angle correction.

Reference: Braunwald’s Heart Disease, 12^th Edition, Page 198