A new imaging technique called photo-acoustic tomography combines the properties of light and sound to give doctors a powerful tool to detect cancer earlier than ever before. Its developers at Washington University in St. Louis say the technique is not only more precise than current imaging techniques like x-ray and CT scans, it is also much safer.
WASHINGTON UNIVERSITY - Called photo-acoustic tomography, the new imaging technique being developed by Professor Lihong Wang of Washington University in Missouri, combines laser light and sound to produce images of unprecedented quality.
"It's actually a way of using sound to detect optical features. Instead of looking at an optical structure we are listening to an optical structure," said Wang, a professor of biomedical engineering.
Wang says light can't penetrate tissue inside the body - instead it gets absorbed by the tissue and scatters. He says that scattered light is the key to photo-acoustic imaging. As the scattered light travels through the tissue it causes a rapid increase in temperature which produces sound waves.
"That rapid temperature rise is going to generate a pressure rise and the pressure will not stand still. The pressure will propagate in biological tissue and outside the tissue we pick up the pressure wave using ultrasound transducers. By detecting the time of the flight, the arrival time of the photo-acoustic signals, we can pinpoint the sound sources which will give you an optical image of what is inside the tissue," he said.
Along with high contrast images of the tissue and organs, Wang says photo-acoustic tomography will give doctors a real-time window into the human body on a molecular level, giving them a powerful tool that can detect signs of cancer before a tumour ever forms.
"So the standard screening for breast cancer screening is x-ray mammography; so first of all it uses ionized radiation and also gives a lot of false positives and that is a huge issue right now. You can imagine all sorts of problems can be created due to the false positives. The hope is by adding more functional information and metabolic information we can indentify real cancers from the false positives," Wang said.
Wang says photo-acoustic tomography will allow doctors to looks for signs of increased oxygen use within tissue, a tell tale sign of possible cancer growth. And he says it
can be done without the dangers of radiation exposure associated with current imaging techniques like x-ray and CT scans.
The imaging technology is currently undergoing its first round of human clinical trials. Professor Wang says photo-acoustic tomography has real potential for saving lives.