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Melanoma is an aggressive skin cancer that often metastasizes, or spreads, to other areas of the body where it forms secondary tumors. These tumors can be more dangerous than the initial tumor itself, thus providing motivation to find ways to detect metastatic cells while they circulate in the blood prior to implantation elsewhere. Single cell detection has proved difficult and many times patients present with large-sized tumors that can be visualized by CT or MRI.

Biomedical engineers at the University of Missouri have just announced the development of, and plans to commercialize, a detection system of circulating melanoma cells in a blood sample. They rely on photoacoustic technology, or laser-induced ultrasound, which the press release describes below:

The scientific underpinning for this invention involves photoacoustics, or laser induced ultrasound. [Principal Investigator John] Viator uses this tool in conjunction with the properties of density, light, heat, and color to cause cancer cells to react in a manner that makes them detectable and different from surrounding cells.

A first step in the testing process is to use a centrifuge to separate a patient's blood into white blood cells and red blood cells. Melanoma cells are about the same density as white blood cells, but less dense than red blood cells, so melanoma cells are naturally thrown in with white blood cells as the blood separates.

The resulting batch of white blood cells (plus any cancer cells present) is then pumped through narrow tubing that contains a tiny glass box, where the cells are hit with a short pulse of high-intensity laser light as they pass by. Since white objects reflect light, the white blood cells are not affected, but any cell with pigment will absorb the light. The intense laser beam heats such a cell rapidly, causing thermo-elastic expansion, which in turn causes the expanding cell to emit a measurable pressure wave. Detection equipment senses this photoacoustic wave and thus locates the cancer cell.

Using this method, a pigmented melanoma cell stands out "like a big black 18-wheeler running down the freeway among thousands and thousands of white Priuses," Viator said. Pigmented melanoma cells can be separated from the healthy white blood cells and then individually tested using biomolecular assays or imaging.

For more information watch the video and follow the links below:

• Press Release From MU's News Bureau: MU Researcher's Photoacoustic Device...
• Press Release From MU's Bond Life Science Center: Patents Photoacoustic Invention...
• Paper and Video in the Journal of Visual Experiments: Detection and Isolation of...

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