Fig. 1

a Schematic diagram of the Fenton reaction equation. b Diagram of penetration depth of light, ultrasound (US) and radiation to human tissues. The light penetrates to a depth of 10 mm, which just only be used for the treatment of shallow tumors, while ultrasound can be used for the treatment of deep tumors with a tissue penetration depth of 10 cm, which can reach to major organs in the body. Although the penetration depth of radiation is deeper than the light and US, it can cause damage to the normal tissue