A custom-made linear array transducer for photoacoustic breast imaging

A custom-made first prototype of a linear array ultrasound transducer for breast imaging is presented. Large active area transducer elements (5 mm x 5 mm) with 1 MHz resonance frequency are chosen to obtain a relatively high sensitivity. Acoustic lenses are used to enlarge the narrow acceptance angle of such transducer elements. The minimum detectable pressure, frequency bandwidth and electrical impedance of the transducer elements are characterized. The results show the transducer has a minimum detectable pressure of 0.8 Pa, which is superior than the transducers used in the Twente Photoacoustic Mammoscope system previously developed in our group. The bandwidth of the transducer is relative small, however it can be improved when using optimized matching layer thickness in future. We also observed a strong lateral resonance at 330 kHz, which may cause problems in various aspects for a photoacoustic imaging system. We discuss the future improvement and plans for the transducer optimizations.