Tissue characterization with intra-arterial ultrasound: special promise and problems.

Although we are able to identify many tissue types based on the screen image in intravascular ultrasound, there is additional information in the ultrasound signal which could be of assistance in characterization and identification of tissue. Intravascular ultrasound has several special characteristics which affect tissue characterization. These include the high transducer frequency, small transducers, short and relatively uniform path to the tissue, and limited tissue types to identify. These characteristics influence the results obtained by absolute backscatter, local statistics, frequency dependent backscatter, and angle dependency of backscatter. These effects are both positive and negative, and in many cases can be observed in clinical imaging. Another area of tissue characterization which can be performed with ultrasound is measurement of arterial wall elasticity. This can be of importance in the evaluation of mechanisms of dilatation, and the potential for complications.