Resolution and material assessment capability of a vibroacoustographicimaging system

There has been significant growth in non-invasive screening techniques for evaluatingabnormal tissue. Vibroacoustography (VA), an imaging modality based onultrasound-stimulated acoustic emission and non-linear scattering characteristics of thetarget, has previously been used to generate relative real-time, pathology-specific imagecontrast between abnormal tissue and normal surrounding tissue; however, an in-depthtissue assessment has yet to be completed. VA utilizes two non-destructive low MHzultrasound tones to produce an acoustic beat frequency in the low kHz range. The acousticradiation force perturbs the target as a function of its mechanical and acousticproperties and the emissive acoustic waves are detected by a nearby hydrophone to form animage based on the viscoelastic characteristics of the target. We have previously reportedthat our VA imaging system can distinguish suspect tissue from normal tissue intissue-mimicking phantoms (TMPs) and ex vivo models with high imagecontrast; however, the goal of this work is to assess the measurement performance andresolution capabilities of this system in pre-clinical models, specifically TMPs in tissueassessment. Lateral and axial resolution, as well as material characterization, studieswere performed on isotropic two-layered and multiple-layered TMP targets. The resolutionstudies resulted in ∼1 mm lateral and ∼12 mm axial, which were confirmed and validated fora confocal transducer geometry. The system showed sufficient measurement performance todetect regions with elastic moduli difference of at least 10 kPa and lateral width of atleast 4 mm. This result, coupled with high imaging contrast, supports the utilization ofVA for potential applications in in vivo medical imaging and tissueassessment for intraoperative applications.