On the feasibility of remote palpation using acoustic radiation force

A method of acoustic remote palpation, capable of imaging local variations in the mechanical properties of tissue, is under investigation. In this met hod, focused ultrasound is used to apply localized ton the order of 2mm(3)) radiation force within tissue, and the resulting tissue displacements are mapped using ultrasonic correlation based methods. The tissue displacements are inversely proportional to the stiffness of the tissue, and thus a stif fer region of tissue exhibits smaller displacements than a more compliant r egion. In this paper, the feasibility of remote palpation is demonstrated e xperimentally using breast tissue phantoms with spherical lesion inclusions , and in vitro liver samples. A single diagnostic transducer and modified u ltrasonic imaging system are used to perform remote palpation. The displace ment images are directly correlated to local variations in tissue stiffness with higher contrast than the corresponding B-mode images. Relationships b etween acoustic beam parameters, lesion characteristics and radiation force induced tissue displacement patterns are investigated and discussed. The r esults show promise for the clinical implementation of remote palpation. (C ) 2001 Acoustical Society of America.