Sonodynamic Therapy
Focused ultrasound may be able to activate sonosensitizers to induce cell death in tumors.
Photodynamic therapy is a technique by which certain chemical agents, known to perfuse well into tumors, are activated by laser light to generate oxygen free radicals which in turn damage DNA and induce apoptosis (programmed cell death) of the tumor cells. This procedure requires the insertion of a fiber optic laser probe into tissue, and is only effective against early stage and localized disease.
Alternatively, focused ultrasound may also be able to activate many of these same chemical agents (called sonosensitizers when they are activated by sound waves). In this sonodynamic therapy process, chemical agents such as 5-ALA, an innocuous dye that is absorbed preferentially by tumor cells, are injected intravenously. Upon application of focused ultrasound to the targeted tumor, the agents induce the same toxic effect as in photodynamic therapy, causing apoptosis of targeted cancer cells.
Sonodynamic therapy could offer advantages as compared to photodynamic therapy by activating these chemical agents in a noninvasive manner. Focused ultrasound has the capability of treating regions deeper in the body where light would either be blocked or require more invasive delivery methods. Focused ultrasound can also provide conformal dosage of energy, and thus induce apoptosis throughout the entire tumor. Furthermore, toxicity can be induced in a precise location while minimizing harm to other areas of the body. Sonodynamic therapy is currently being used in clinical trials to treat patients with diffuse intrinsic pontine glioma, glioblastoma, and biliary tract tumors.
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