In vivo demonstration of acoustic radiation force impulse (ARFI) imaging in the thyroid, abdomen, and breast
Acoustic Radiation Force Impulse (ARFI) imaging is proposed as a method for characterizing local variations in tissue mechanical response. In this method, a single ultrasonic transducer array is used to both apply localized radiation forces within tissue and to track the resulting displacements. Tissue displacement is inversely proportional to tissue stiffness, and the temporal response of tissue to radiation force varies with tissue type. We have previously presented results generated using radiation force applied in a single pushing location in vivo, and using multiple pushing locations in tissue phantoms where the data was acquired over several minutes. In this paper, data are presented that were acquired using multiple applications of radiation force to interrogate an extended region of interest in a real-time data acquisition implementation, using beam sequences similar to those used for Color Doppler. In vivo ARFI images of the thyroid, abdomen, and breast are presented. Peak displacements of 5, 10, and 8 microns were observed in the these tissues, respectively. In all cases, the ARFI images and matched B-mode images show highly correlated structural information, and comparable resolution. Images of the thyroid exhibit remarkable uniformity in displacement with no speckle. The results suggest considerable clinical potential for ARFI imaging.
