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Laser imaging may offer a new tool for bone cancer surgery

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“Laser imaging may offer a new tool for bone cancer surgery”

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Of the many ways to treat cancer, the oldest, and perhaps the most proven, is surgery. Even with the advent of chemotherapy, radiation, and more experimental treatments like bacteria that seek out and destroy cancer cells, cancers, very often, simply need to be cut out of a patient’s body.

The goal is to remove all cancerous tissue while preserving as much surrounding healthy material as possible. But because it can be difficult to draw a clear line between cancerous and healthy tissue, surgeons often err on the side of caution and remove healthy tissue to make sure they’ve removed all cancerous tissue.

This is particularly problematic when a patient has a cancer that affects the bones; bones present unique challenges during surgery because of their hardness compared to other tissues and because they grow back much more slowly than other tissue types.

“It’s very difficult to grow bone, so if you cut bone, you basically lose it,” says Lihong Wang, Bren Professor of Medical and Electrical Engineering.

New diagnostic imaging technology developed by Caltech researchers gives surgeons the ability to make 10 times more precise cuts, allowing them to preserve up to 1,000 times more healthy tissue and aiding patient recovery .

Traditional methods used to determine if a piece of bone contains cancer cells take time. The piece of bone is removed and sent to a lab where its hard calcium matrix is ​​slowly dissolved, leaving only the living cells. The remaining material is then sliced ​​and imaged. Because the process can take anywhere from one to seven days, surgeons cannot rely on it during surgery to determine the health of the bone around and near a tumor, and so they will get even more out of it than needed – and more than they would in softer tissues that can be quickly biopsied.

The new imaging technology, called real-time 3D contour scanning ultraviolet photoacoustic microscopy, or UV-PAM, is intended to replace the traditional method of identifying cancerous bone tissue. Since the process only takes a few minutes, it allows the surgeon to differentiate healthy bone from cancerous bone during the operation.

Like other photoacoustic imaging technologies developed by Wang, UV-PAM works by using laser light to vibrate molecules in living tissue. These vibrations occur at ultrasound frequencies and can be used to image tissues and organs in the same way that these ultrasounds are used to image a developing fetus.

UV-PAM uses the ultraviolet wavelengths of tuned laser light to vibrate DNA and RNA molecules. Because cancer cells are structured differently, denser and contain much more DNA than healthy cells, an area of ​​cancerous tissue will absorb more UV light and thus provide a stronger ultrasound signal than healthy tissue, allowing the surgeon to clearly identify the bony areas that need to be removed.

“We can deliver results in 11 minutes, so they know exactly where to cut,” says Wang.

The technology provides doctors with an image of the bone that they have scanned and formatted to resemble images created by traditional biopsy techniques.

“We’re just presenting images to pathologists,” says Wang. “They use the same pattern recognition in their own brains to figure out what’s cancerous and what’s healthy. That’s their training.”

Currently, the technology is only demonstrated in the laboratory. Wang says he hopes to bring it to the real world where it can be used on patients, but he plans to make some improvements first.

“We would like to give it even finer spatial resolution and higher imaging speed so that we can even see some details in the cell nucleus faster,” he says. “Can we go beyond standard pathology? We are working on it.

Reference: Cao R, Nelson SD, Davis S, et al. Label-free intraoperative histology of bone tissue by deep learning-assisted ultraviolet photoacoustic microscopy. Nat Biomed Eng. 2022:1-11. do I: 10.1038/s41551-022-00940-z

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