Newswatch: March 2006

Scientists use near-infrared laser light to detect cancerous breast tissue

A team of scientists from the City College of New York (CCNY) and Memorial Sloan-Kettering Cancer Center (New York) has successfully used near-infrared laser light to differentiate between cancerous and noncancerous human breast tissue. The development could lead to noninvasive techniques for detecting and diagnosing breast cancer.

"Near-infrared imaging is a noninvasive technique that has several advantages over mammography," said Swapan K. Gayen, PhD, associate professor of physics at CCNY and research team member. "It has the potential to diagnose cancer, whereas mammography can only detect a tumor but not specify whether it is benign or malignant."

Under current protocols, when a mammogram shows the presence of a tumor, patients are sent for biopsies to extract a tissue sample for diagnosis. According to Gayen, in 80% of those cases, cancer is not found. Additionally, he added that mammography is less effective at detecting tumors in women with an abundance of dense glandular tissue in the breast. More research is necessary to determine whether optical imaging can overcome this problem.

"Laser light's salient features, such as spectral brightness, monochromaticity, polarization, coherence, and wavelength tenability, make it a promising technology for noninvasive and minimally invasive cancer detection and diagnosis," said Robert R. Alfano, PhD, professor of science and engineering at CCNY and research team member who heads the Institute for Ultrafast Spectroscopy and Lasers (IUSL) at CCNY. "We are searching for the key wavelengths and time zones to detect cancer."

Other cancer-related investigations conducted by the IUSL include noninvasive techniques for the detection of prostate cancer tumors and skin cancer, as well as a "photonic pill" that would transmit signals from inside the body after being swallowed by a patient.

The breast-cancer researchers used a technique known as time gating to capture images produced by three different groups of photons after they passed through ex vivo (nonliving) samples of cancerous and normal breast tissue. Photons scatter in different directions as they pass a scattering medium, such as breast tissue.

The photons that take the most direct routes, called ballistic components, produce different kinds of images than "snake" and diffuse components, which take more circuitous paths. The images produced by the ballistic and early snake slices of transmitted light highlighted tumors; those produced by the late snake and diffuse components accentuated normal tissue.

The time-resolved imaging experiment involved the use of 120-femtosecond, 1-KHz-repetition-rate, and 800-nanometer light pulses generated by a Ti:sapphire laser, to illuminate the tissue samples, as well as an 80-picosecond-resolution ultrafast gated intensified camera system to record 2-D time-sliced images. A femtosecond is 10-15 of a second, a picosecond is 10-12 of a second, and a nanometer is one-billionth of a meter.

Over the coming year, the research team plans to conduct further testing, optimizing the inverse-reconstruction approach to obtain a 3-D image of a "model breast" approximating the size of an average female breast, according to Gayen. He added that the team hopes to begin in vivo tests by 2007 that, if successful, could lead to commercial development.

The project was conducted under a grant from the US Army Medical Research and Material Command's Breast Cancer Research Program.