Resolution Issues in Medical Ultrasound

A common figure of merit for imaging systems is resolution--the ability to differentiate two or more closely spaced point targets. When applied to ultrasonic images for medical applications, however, it is not an adequate measure of performance. The clinical user is also concerned with differentiating subtle textural changes in tissue. We refer to this figure of merit as contrast resolution. This paper reviews basic principles of ultrasonic beam formation in a tutorial fashion, and explores the systematic requirements and trade-offs necessary to achieve good contrast resolution along with good detail resolution. Simulation results are presented.