Fig. 1. Experimental system designed by the Oeri group. (a) System block diagram; (b1) maximum intensity projection of peripheral toe joint and distal interphalangeal joint; (b2) axial slice display of left little finger; (b3) left little finger of healthy volunteer^[39]

Fig. 2. Experimental system designed by our group and imaging results. (a) System block diagram; (b) photoacoustic image of the intraocular copper-wire and the inserted is the photograph of the copper wire; (c) photoacoustic imaging of brain cortical vasculature of the rabbit, where the inset is the open-skull photograph of the rabbit brain after experiments ^[44-47]

Fig. 3. Photoacoustic images of the volunteer's right hand. (a) Maximum amplitude projection of the photoacoustic signals along the Z-axis; (b) color encoded depth image of the hand ^[50]

Fig. 4. Experimental system designed by the Nagae group and photoacoustic imaging of the limbs. (a) Experimental device and data acquisition block diagram; (b) palm; (c) back of hand; (d) forearm; (e) outside of thigh; (f) calf; (g) toe; (h) foot sole; (i) b-h corresponding position ^[51]

Fig. 5. Experimental system designed by Heijblom group and experimental results. (a) System block diagram; (b)-(e) MRI (left) and PAT (right) data reconstruction of two cases of thymus in the head and tail position^[63]

Fig. 6. Experimental system designed by Tang group and the changes of the blood oxygen concentration in the brain. (a) Structure of wearable ultrasonic transducer; (b) design of the system diagram; (c) behavioral capabilities under a wearable ultrasonic transducer; (d) total cerebral hemoglobin images; (e) oxygen saturation in plane^[65]