A combined indenter/ARFI imaging system
The goal of this project is to develop an integrated indenter-ARFI (acoustic radiation force impulse imaging) system. The system is capable of acquiring matched datasets from ex vivo tissue samples, which will be used to evaluate excised colorectal tumors and blood vessels with atherosclerosis. This system will facilitate correlation of ARFI images of tissue samples with independently characterized material properties. We hypothesize that for a fixed indenter stress, the measured tissue displacements will be correlated with the ARFI generated displacements, which are inversely proportional to the stiffness of the tissue. A 100 Bloom gelatin phantom with a 300 Bloom surface lesion was used to test the system. Four indenter tips with different sizes were used to scan across the lesion phantom. Smaller tip diameters provide improved lesion edge definition for a given lateral sampling; for a given indenter tip, closer lateral sampling also improves lesion edge definition. For ARFI imaging, displacements were calculated at 0.35ms after ARFI excitation. To compare the results from the two systems, ARFI data was averaged axially along a 2 mm window starting at the sample surface, and compared with the indenter displacements at a given stress. Good agreement is observed between the ratio of displacements inside and outside of the stiff inclusion, for both the phantom and ex vivo colon cancer samples. © 2005 IEEE.
