Together with other parameters that can be measured in the photoacoustic images, such as vessel cross-section, concentration of hemoglobin and blood flow speed, the gradient of oxygen saturation can be used to calculate the oxygen use by a region of tissue.
The imaging technique most widely used to measure oxygen use is positron emission tomography (PET), which requires the injection or inhalation of a radioactively labeled tracer and undesirable radiation exposure.
Last year in the Journal of Biomedical Optics, Wang's team demonstrated that oxygen metabolism betrayed the presence of a melanoma (a skin cancer) and of a glioblastoma (a brain tumor) within a few days of the injection of tumor cells in an animal model. Oxygen use doubled in a week.
"Because hypermetabolism is a quintessential hallmark of cancer," Wang says, "photoacoustic imaging may allow cancer to be detected at the earliest stage without using a foreign contrast agent."
Wang will be speaking about photoacoustic tomography at the annual meeting of the American Association for Cancer Research (AACR) this spring.
A singular vision
Wang, who has worked on photoacoustic imaging for more than 10 years, sees a subtler but ultimately even more transformative advantage to the technology.
"Every issue of every top journal publishes exciting lab discoveries," he says, "but only a tiny fraction of them are ever translated into clinical practice." Part of the problem is that images are made by different methods at different scales, making comparisons across scales difficult.
"In current practice," he says, "we use optical microscopy to examine organelles and cells and nonoptical imaging techniques such as X-ray tomography for tissues and organs. None of the clinical imaging technologies give you the strong contrast of
|Contact: Diana Lutz|
Washington University in St. Louis