Liver stiffness measurement techniques: Basics
Liver stiffness measurements can be estimated by multiple techniques. This chapter describes the basic principles of the various methods. The strain elastography techniques are briefly described as the acoustic radiation force imaging (ARFI) technique is not used for liver stiffness measurements, but the manual displacement method has been used. The shear wave elastography (SWE) techniques—vibration controlled transient elastography (VCTE), point SWE (pSWE), and 2-dimensional SWE (2DSWE)—are widely used for liver stiffness measurement. To differentiate VCTE, which uses a mechanical pulse to generate shear waves, from the techniques using acoustic radiation force (ARF) to generate the shear waves, pSWE and 2D-SWE are listed as ARF techniques. It is important to understand the principles of how the measurements are made to understand (1) why the protocols were developed, (2) how and where artifacts occur, and (3) how to optimize the estimate of liver stiffness. Key points that are important takeaways to understand making liver stiffness estimation are listed. We also briefly describe magnetic resonance elastography as this technique is also used for liver stiffness and is discussed in the book to compare it to the ultrasound techniques.
