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Seeing the Invisibleby Ruth SoRelle, M.P.H. 
Drs. Eva Sevick and Shi Ke In the first Gulf war, television viewers watched, mesmerized as bombs dropped by U.S. planes flashed a deadly green viewed through night-vision technology. Today, Dr. Eva Sevick and her diverse team of experts in the Baylor College of Medicine Department of Radiology's Division of Molecular Imaging are attempting to determine if similar technology can identify the spread of breast cancer to lymph nodes– without surgical biopsy. Although she has done extensive animal testing, it's the first time the BCM professor of radiology has applied this technique to humans. Working with researchers in the Baylor Breast Center, she is combining near-infrared light with a special dye and an adaptation of technology used in digital cameras to look for spreading malignancy in the lymph nodes of women with breast cancer. (Near-infrared light is just beyond visible light in the spectrum.) "If you have breast cancer, oncologists want to know if it has spread to your lymph nodes," said Sevick. The nodes collect lymph, fluid that drains from the area of the tumor. If cancer has spread to the lymph nodes, then cancer specialists become more aggressive in treating patients. "We take this near-infrared fluorescent dye and tag it onto something that goes right to breast cancer cells in the lymph," she said. "Then we inject the dye into the lymph area. Using our near-infrared light, we illuminate those areas. The fluorescent dye identifies the positive lymph nodes. The idea is that eventually you may not have to have surgery to identify the cancer cells in lymph nodes." Ideally, the technique could allow identification of very small collections of cancer cells in lymph nodes called micrometastases. Currently, surgical biopsy is the only way to determine with certainty if a lymph node has malignant cells in it. The key to molecular imaging is targeting a specific molecule known to be involved in a particular disease. In this case, the dye contains materials that seek out particular molecules known to be involved in breast cancer. 
Dr. Wei Wang Before she can use the material in people, Sevick tests it in cells in the laboratory and then in small animals. "We are lucky in that, at Baylor, we have that rare instance where we encompass that whole pipeline– laboratory cell cultures, animals and patients," she said. In animal studies, this kind of imaging is already enabling researchers to watch a drug as it is distributed throughout the body, determining where it goes, how long it stays and whether it is toxic. These are critical issues that must be addressed through imaging. Sevick expects to take the technique into many kinds of studies and diseases. She sees the possibility of tracking the course of stem cells or immune system cells used in the treatment of many kinds of cancer or detecting blood vessel changes that can signal heart disease. Unlike nuclear imaging, near-infrared optical imaging does not use a radioactive tracer. When doctors use a radioactive tracer as an imaging agent, it gives off a signal that is collected by a camera at one point in time. In optical imaging, the fluorescent dye is excited by a dim red light to give off a light signal. That signal is collected by a sophisticated imager similar to the imaging technology in a digital camera but far more sensitive. There it records the light. The fluorescent dye can be excited again and again, enabling researchers to record its movement as molecular events take place. The near-infrared light can go through several centimeters of tissue, making it possible to watch molecular events deep inside the body—as is happening in the study to detect cancer in the lymph nodes of women with breast cancer. Sevick expects to take the technique into many kinds of studies and diseases. She sees the possibility of tracking the course of stem cells or immune system cells used in the treatment of many kinds of cancer or detecting blood vessel changes that can signal heart disease. Currently, she is exploring the potential of tracking viruses used to take genes into cells as part of gene therapy. "One of the problems with gene therapy is how to get the viruses to where they are supposed to go. If we tag them with a near-infrared dye, we can monitor the therapy as it's going on. If the virus is not going where it's supposed to, you would know. It's a way to individualize and personalize medicine," said Sevick. 
Kildong Hwang and Sevick A chemical engineer by training, she always knew she would work in biomedicine. She sees a convergence of science and engineering disciplines coming together in her field and others. She has gathered together a host of people with varying talents who have made the work possible. "We built our optical imaging setup ourselves," she said. "Our research group has also developed the computer programs and mathematical formulas that allow us to recreate images in three dimensions on the computer, a process known as tomography. "All the people in this laboratory are trained differently," she said. For example, Dr. Shi Ke is a physician trained in surgery and serves as director of the Frensley Imaging Center at BCM. Drs. Amit Joshi and Ranadhir Roy are experts in tomography with a doctorate in engineering and mathematics. Dr. Wei Wang is a chemist by training and generates the molecular imaging agents. She learns from all of them as they learn from her stating that "every day I come in, I feel like a student all over again." Sevick sees the opportunity to introduce physicians in training to new imaging methodologies as one of the greatest opportunities to advance the field "A big part of this program is to prime the pump with people who understand molecular imaging and can use it in the clinic." |
Patient CareResearchTrekking Into New Territory: Translational Biology and Molecular Medicine Closing the Gap Between Lab and Clinic EducationTulane's Journey Back to New Orleans Community ServiceAlumni & DevelopmentCollege News
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Volume 2, Issue 2, Summer 2006 |
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