MUNICH, Germany, Sept. 21, 2011 — A new imaging technique is helping to locate even small groups of cancer cells that surgeons might otherwise overlook during surgery. The technique uses laser light to find cancer cells based on their molecular signatures, and there are plans to apply the technique to minimally invasive and endoscopic procedures.
Ovarian cancer is one of the most common types of cancer found in women. As tumors can initially grow unchecked in the abdomen without causing any major symptoms, patients are usually diagnosed at an advanced stage and must undergo surgery and chemotherapy. To improve each patient’s prognosis, surgeons attempt to remove all traces of the tumors. However, they primarily have to rely on visual inspection and palpation, which is an enormous challenge, especially in the case of small tumor nests or remaining tumor borders after the primary tumor excision.
A new multispectral fluorescence imaging system can visualize ovarian cancer cells during surgery. (Photo: TUM Mitarbeiter)
A team of researchers from Technische Universität München, Helmholtz Zentrum München and University of Groningen, led by Vasilis Ntziachristos, carried out a study on nine ovarian cancer patients. Before the operation, the patients were injected with folic acid chemically coupled to a green fluorescent dye. Most ovarian tumors have a protein — folate receptor alpha — on their surface that bonds with folic acid and transports it inside the cell. During abdominal surgery, the surgeon can then shine a special laser light onto the patient’s ovaries, causing the labeled folic acid inside the cancer cells to emit light. Healthy tissue remains dark.
Surgeon’s view of ovarian cancer cells with and without the tumor-targeted fluorescent imaging agent. (Photo: Gooitzen van Dam)
The fluorescent cancer cells, however, cannot be detected by the naked eye. Three cameras, mounted on a pivoting support arm over the operating table, detect optical and fluorescent signals at multiple spectral bands and then correct for light variations due to illumination and tissue discolorations to provide truly accurate fluorescence images that can be simultaneously displayed with corresponding color images on monitors in the operating room. The surgeon can thus check whether all the cancer cells have been removed by inspecting for vestiges of fluorescent light. In eight of the nine patients, doctors removed small clusters of tumor cells that might otherwise have gone undetected.
The researchers want to further develop the camera system so it can be used to detect other forms of tumors during operations. Of significant importance in future developments is the ability to offer accurate fluorescence imaging so that the data collected reflects true presence of disease.
“The use of advanced, real-time optical technology will allow us to standardize data collection and accuracy so that studies performed at multiple clinical centers can be accurately compared and analyzed,” Ntziachristos said.