Radiation force imaging: Challenges and opportunities
A number of novel imaging modalities have been developed to interrogate the mechanical properties of tissue. A subset of these methods utilize acoustic radiation force to mechanically excite tissue and form images from the local responses of tissue to these excitations. These methods are attractive because of the ability to focus and steer the excitatory beams and to control their spatial and temporal characteristics using techniques similar to those employed in conventional ultrasonic imaging. These capabilities allow for a wide variety of imaging methods whose features are only beginning to be explored. However, radiation force based methods also present significant challenges. Tissue and transducer heating limit the tissue displacements achievable with radiation force applications and restrict image frame rates and fields-of-view. The small tissue displacements are difficult to detect and may be obscured by physiologic tissue motion. We review the fundamental limits of imaging methods based on radiation force generated by patient safety concerns and the impact of these limits on achievable image signal-to-noise ratios and frame rates. We also review our progress to date in the development and clinical evaluation of one class of radiation force imaging methods employing very brief impulses of radiation force.
