Multispectral Camera Detects Tumors During Surgery

A multispectral camera that simultaneously displays several fluorescent dyes and the reflectance image in real time could help surgeons ensure that they don't leave behind tiny pieces of malignant tumors.

Obviously, cancer patients have a better chance of recovering if their tumors are completely removed. But tiny clusters often are difficult for surgeons to recognize and remove, and the margins between malignant and healthy tissue are difficult to differentiate.

A new camera helps visualize such tumors by displaying fluorescent molecules that "paint" the cancer tissue and make it obvious; until now, surgeons have had to rely exclusively on what they see. The device also helps identify delicate nerves and major arteries that need to be avoided because the dye also affects them. The surgical aid was developed at the Fraunhofer Project Group for Automation in Medicine and Biotechnology (PAMB), a unit of the Fraunhofer Institute for Manufacturing Engineering and Automation (IPA).

The new camera displays colored structures (left) by means of fluorescent dyes (blue and green areas shown here). Courtesy of ©Fraunhofer IPA.

The fluorescent molecules are injected into the patient's circulation system before an operation and selectively attach to the tumor during their trip through the body. If the corresponding area is then illumimated with a specific wavelength, fluorescence is emitted and the malignant tissue glows green, blue, red or any other color, depending on the injected dye, while the healthy tissue appears the same. This makes it easy to see tumor cells with the naked eye.

“The operator receives significantly more accurate information. Millimeter-sized tumor remnants or metastases that a surgeon would otherwise possibly overlook are recognizable in detail on the monitor. Patients operated on under fluorescent light have improved chances of survival,” said Dr. Nikolaos Deliolanis, head of the Biomedical Optics Group at PAMB.

The technique requires only one camera and one set of filters for its photographs, which can visualize up to four dyes simlutaneously. Software developed in-house analyzes and processes the images in seconds and presents it continuously on a monitor during surgery. The information from the fluorescent image is superimposed on the normal color image.

“The visibility of the dye to the camera depends in large part on the selection of the correct set of fluorescence filters. The filter separates the incident excitation wavelengths from the fluorescing wavelengths so that the diseased tissue is also set apart from its surroundings, even at very low light intensities,” said Nikolas Dimitriadis, a scientist at PAMB.

The team envisions the system being integrated into various medical imaging systems, such as surgical microscopes and endoscopes. One dye preparation available now, 5-amino levulinic acid (5-ALA), is used especially for glioblastomas, "one of the most frequent malignant brain tumors in adults," Dimitriadis said. The dye makes the brain tumors glow red to be detected by the camera.

The multispectral fluorescence imaging system could be approved for use in humans as soon as next year, the researchers say, with the first clinical trials for glioblastoma patients planned for 2014.

A prototype of the system will debut Nov. 20-23 at the Medica Trade Fair in Düsseldorf in the joint Fraunhofer booth (Halle 10, Booth F05).

For more information, visit: www.fraunhofer.de