Fig. 1. Control block diagram

Fig. 2. Schematic of experimental setup

Fig. 3. Light source of PTT system. (a) Overall optical path; (b) pulse laser; (c) continuous laser

Fig. 4. Integrated probe. (a) Lateral view of the probe; (b) light exit of the probe; (c) 3D model of the integrated probe

Fig. 5. Power control module of the PTT system

Fig. 6. Physical map of experimental phantom. (a) Side view of the phantom; (b) top view of the phantom; (c) the control variable

Fig. 7. Peak-to-peak value of photoacoustic signal of phantoms

Fig. 8. Linear relationship between temperature and photoacoustic signal of each phantom. (a) Control group 1; (b) control group 2; (c) control group 3; (d) control group 4; (e) control group 5; (f) control group 6

Fig. 9. Variation of photoacoustic signal with temperature

Fig. 10. Photoacoustic image of vascular phantom

Fig. 11. Photoacoustic images and sampling signals at different temperatures. (a) Photoacoustic image at 31 ℃; (b) photoacoustic image at 36 ℃; (c) photoacoustic image at 41 ℃; (d) photoacoustic signal at 41 ℃; (e) photoacoustic signal at 36 ℃; (f) photoacoustic signal at 31 ℃

Fig. 12. Distribution curve of intensity values in photoacoustic image matrix

Fig. 13. Linear fitting result between photoacoustic data and actual temperature of phantom. (a) Sensitive point of photoacoustic temperature; (b) average pixel value

Fig. 14. Multimodal reconstruction. (a) Photoacoustic image; (b) ultrasound image; (c) temperature distribution image

Fig. 15. Temperature of human tissue phantom

Fig. 16. Deviation of measured temperature for human tissue phantom

Fig. 17. Temperature measured by thermocouple and photoacoustic method