BALTIMORE—In a recent Science Translational Medicine paper, a team of Johns Hopkins researchers have detailed a new imaging method that could make brain surgeries to remove cancer easier—by color-coding the the healthy and cancerous areas. The paper, titled “Detection of human brain cancer infiltration ex vivo and in vivo using quantitative optical coherence tomography,” appeared online June 17.
The basis of this approach lies with optical coherence tomography (OCT), an imaging technology first developed in the early '90s for imaging the retina. This technology operates on the echolocation principle used in ultrasound scanners, though it releases light as opposed to sound waves and provides higher-resolution images than ultrasound does. As an added bonus, patients who undergo OCT aren't exposed to ionizing radiation as with X-ray, CT scans or PET scans.
Carmet Kut, an M.D./Ph.D. student working in the lab of Dr. Xingde Li, a professor of biomedical engineering, posited that OCT might offer a new way to differentiate brain cancer from healthy tissue during surgery. Li is leading one of many groups globally that have been exploring OCT's potential in organs other than the eye.
Kut's hypothesis was that given that cancers tend to be fairly dense, they should scatter and reflect lightwaves differently than healthy tissue. For three years, Kut, Li and Dr. Alfredo Quinones-Hinojosa, a professor of neurosurgery, neuroscience and oncology at the Johns Hopkins University School of Medicine and the clinical leader of the research team, worked with this principle, until they discovered a better approach: brain cancer cells lack the myelin sheaths that coat healthy brain cells, a property that provided a more pronounced effect on OCT readings than cellular density.
With that new direction in mind, the team determined the “signature” of brain cancer on an OCT scan, then developed a computer algorithm that could process OCT data and rapidly produce a color-coded map of the brain; healthy tissue would appear green, while cancerous tissue is red. According to Li, their thought is that “the OCT would be aimed at the area being operated on, and the surgeon could look at a screen to get a continuously updated picture of where the cancer is — and isn’t.”
The system has been tested in surgeries to remove brain tumors from mice, according to Kut, and on fresh human brain tissue removed during surgeries. The ex-vivo human brain tissues came from 32 patients with grade II to grade IV brain cancer, and five patients with non-cancer brain pathologies. As reported in the paper, “OCT achieved high sensitivity and specificity at an attenuation threshold of 5.5 mm−1 for brain cancer patients.” The system “was capable of processing and displaying a color-coded optical property map in real time at a rate of 110 to 215 frames per second, or 1.2 to 2.4 s for an 8- to 16-mm3 tissue volume, thus providing direct visual cues for cancer versus non-cancer areas.”
The goal is to begin applying this system in clinical trials in patients this summer. Kut noted that this method could be adapted for use in other parts of the body, and is exploring the potential of combining OCT with another imaging technique that could detect blood vessels, allowing surgeons to avoid them during surgery.
The American Brain Tumor Association estimates that 70,000 new cases of brain cancer will be diagnosed this year. The most common primary brain tumors are meningiomas (representing 34 percent of all primary brain tumors), gliomas (30 percent of all brain tumors and 80 percent of all malignant tumors) and glioblastomas (17 percent of all primary brain tumors). Thirty-four percent of primary tumors, the site notes, are located within the meninges, which surround the brain and spinal cord and protect the central nervous system. Twenty-two percent are found in the frontal, temporal, parietal and occipital lobes, which control functions such as thinking and decision-making, hearing, processing sensory information associated with taste, temperate and touch and processing visual information, respectively. Given the functions these sections of the brain are responsible for, it's clear why an imaging technique that could allow for more accurate, thorough cancer resection could be huge.
“As a neurosurgeon, I’m in agony when I’m taking out a tumor. If I take out too little, the cancer could come back; too much, and the patient can be permanently disabled. We think optical coherence tomography has strong potential for helping surgeons know exactly where to cut,” Quinones-Hinojosa said in a press release.