Photoacoustic imaging promises breast cancer screening without ionizing radiation
By Darren Quick
May 10, 2012
While breast cancer screening tests are accepted as safe – and we definitely wouldn’t want to scare anyone off from a potentially life-saving test – they do have some risks associated with them. The most obvious being the exposure to low doses of ionizing radiation, which in itself is a risk factor for breast cancer. X-ray mammography can also give false positive and negative results. In the quest for a safer, more accurate alternative, Dutch researchers have provided proof of concept that photoacoustic imaging can be used to detect and visualize breast tumors.
Photoacoustic imaging is a hybrid optical and acoustical imaging technique in which biological tissue is exposed to non-ionizing laser pulses. Because malignant tissue absorbs more light, it increases in temperature and expands when exposed to the laser pulses. This thermal expansion creates a pressure wave that can then be detected and converted into an image using ultrasound.
Using this approach, researchers from the University of Twente and Medisch Spectrum Twente Hospital in Oldenzaal created a specialized device called the Twente Photoacoustic Mammoscope (PAM) and built it into a hospital bed so the patient can lay prone while laser light at a wavelength of 1,064 nanometers scans her breast. An ultrasound detector placed on one side of the breast detects the photoacoustic signals, which are then processed by the PAM system and reconstructed into images. Areas of abnormally high intensity will indicate malignant tissue, while areas of low intensity will indicate benign tissue.
When they compared the performance of the system with conventional diagnostic X-rays, ultrasound imaging, MRI, and tissue exams, the researchers found that malignancies produced a distinct photoacoustic signal. Additionally, the photoacoustic contrast of the malignant tissue was found to be higher than the contrast provided by conventional X-ray mammographies.
"PAM needs some technical improvements before it is a really valuable clinical tool for diagnosis or treatment of breast cancer,” said Michelle Heijblom, a Ph.D. student at the University of Twente. “Our next step is to make those improvements and then evaluate less obvious potential tumors, benign lesions, and normal breasts with it."
The research team’s paper appears in the Optical Society’s open-access journal Optics Express.
Source: The Optical Society