The gist: Cancer can be detected using a technique called photoacoustic imaging. This technique gives a doctors clear pictures of the inside of the body so they can detect tumors. However, use of this technique has been limited because improving it would require potentially toxic ‘photosensitizer’ molecules to increase the resolution of the pictures. Now, researchers have found a low-toxicity photosensitizer that could safely enhance photoacoustic imaging for cancer detection.
“Concerns over toxicity have constrained the clinical application of photoacoustic imaging—a new experimental technique used to detect tumors lurking among healthy cells. A*STAR researchers from the Singapore Bioimaging Consortium and an international team have now discovered how to improve both the safety and the tumor-locating efficacy of photoacoustic imaging using ‘photosensitizer’ contrast agents.
“Unlike typical optical measurements, photoacoustic imaging can probe deep into tissue by using ultrasonic waves generated by laser light pulses. This hybrid method produces strikingly clear pictures of complex biosystems, such as vascular tumor networks in organs and tissues. However, clinical applications of photoacoustic imaging have been limited by safety concerns surrounding ‘contrast agents’—light-absorbing molecules injected into cells to enhance imaging resolution.
“Photosensitizers are molecules that play key roles in a cancer treatment known as photodynamic therapy. These nontoxic substances, which are normally based on conjugated aromatic ring systems, specifically bind to malignant cells while leaving healthy tissue untouched. Exposing a photosensitizer to laser light causes it to produce excited-state oxygen molecules, which react with diseased cells to kill them. The photosensitizer is then rapidly eliminated from the target tissue.”