A sensitive ultrasonic imaging method for targeted contrast microbubble detection

We have recently developed a targeted imaging technique for selective and sensitive ultrasound molecular imaging by taking advantage of wideband transient high frequency acoustic emission from ultrasound contrast agents. The imaging modality makes use of a novel multi-frequency co-linear array (two outer 1.4MHz and one center 5.3MHz arrays) transducer integrated with the Siemens AntaresSystem. The imaging sequence includes a B-mode imaging pulse sequence in which a short pulse is transmitted with the outer low frequency arrays and received with the inner high frequency array (TLRH: transmit at low frequency and receive at high frequency), followed by a long radiation force pulse to induce immediate bubble adhesion using the center array, and a second B-mode imaging pulse sequence. The RF data obtained from the second B-mode pulse sequence are averaged and then subtracted from the first B-mode sequence. The imaging technique was tested in a targeted imaging phantom, where lipid-shelled biotin microbubbles flow within an avidin coated-cellulose. Results showed that tissue signals were suppressed up to 33 dB and a targeted bubble contrast-to-free bubble signal ratio of up to 23 dB was obtained from the composite sequence imaging.