Ring array transducer

A transducer ring array for volumetric ultrasound imaging, the ring array comprising:

• a set of radially extending first channels, wherein each first channel comprises a plurality of outer CMUT drums, a plurality of inner CMUT drums, and a respective radiofrequency, RF, line that connects to the pluralities of outer and inner CMUT drums;
• a set of radially extending second channels, wherein each second channel comprises only a plurality of outer CMUT drums, and a respective radiofrequency, RF, line that connects to the plurality of outer CMUT drums;
• and
• a biasing system comprising, for each of the first channels, a biasing line for applying a bias to the plurality of outer CMUT drums, and a biasing line for biasing the plurality of inner CMUT drums that is individually addressable from the biasing line for applying a bias to the plurality of outer CMUT drums, or wherein the biasing system comprises a circuit configured to be capable of only providing a bias to either the plurality of outer CMUT drums or the plurality of inner CMUT drums;
• the biasing system further comprising, for each of the second channels, a biasing line connected to the plurality of outer CMUT drums for applying a bias to the plurality of outer CMUT drums;
• wherein each second channel is arranged in between a pair of first channels;
• wherein the plurality of outer CMUT drums of both the first channels and the second channels form an outer ring, and wherein the plurality of inner CMUT drums of the first channels form an inner ring, wherein an inner diameter of the outer ring is larger than an outer diameter of the inner ring.