A dual-frequency co-linear array for prostate acoustic angiography

Approximately 80% of men who reach 80-years of age will have some form of prostate cancer. The challenge remains to differentiate indolent from aggressive disease. Based on recent research, acoustic angiography, a novel contrast enhanced ultrasound imaging technique, can provide high-resolution visualization of tissue microvasculature and has demonstrated the ability to differentiate vascular characteristics between healthy and tumor tissue. We hypothesize that transrectal acoustic angiography may enhance assessment of prostate cancer. In this paper, we describe the development of a dual layer co-linear array ultrasound transducer for transrectal acoustic angiography. The KLM model and Field II were used for the element design and acoustic field simulation, respectively. The probe consists of 64 transmit elements with a center frequency of 3 MHz and 128 receive elements with a center frequency of 15 MHz. The dimensions of the array are 18 mm in azimuth and 8 mm in elevation. The pitch is 280 μm for transmitting (TX) elements and 140 μm for receiving (RX) elements. Pulse-echo test of TX/RX elements were conducted and compared with the simulation results. Real-time contrast imaging was tested using a Verasonics system. Non-linear responses from microbubble contrast agents at a depth of 18 mm were clearly observed. The axial beam width (-6 dB) and CTR were calculated from the measured signals to be 400 μm and 20 dB, respectively. These results suggest that the prototype co-linear array is capable of performing dual-frequency superharmonic imaging of microbubbles for prostate cancer assessment.