Provided herein is a probe for ultrasound imaging of tissue. The probe comprises an optical relay having an optically absorbing coating at the distal end of the probe for generating ultrasound from excitation light via the photoacoustic effect, wherein the generated ultrasound propagates as an ultrasound beam into the tissue; and an ultrasound receiver separate from the optical relay. The optical relay is configured to receive as input a time-varying spatial pattern of excitation light at the proximal end of the probe and to transmit the excitation light to the distal end of the probe to illuminate the optically absorbing coating in accordance with said time-varying spatial pattern, thereby generating ultrasound from the excitation light via the photoacoustic effect to propagate as a scanning ultrasound beam into the tissue. The ultrasound receiver is configured to receive reflections of the ultrasound from tissue. Such an ultrasound probe may be incorporated, for example, into a transseptal puncture needle.