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NIR light maps breast cancer

19 Nov 2003

Researchers in the US develop a near-infrared imaging system that could help detect breast cancer.

A near-infrared imaging system being developed in the US could aid the detection of breast cancer, according to its inventors. The researchers from US firm ViOptik and Massachusetts General Hospital (MGH), also in the US, say their P-Scan system can be used in conjunction with mammography to detect tumors and minimize the number of biopsies that are performed. (Applied Optics 42 6412)

Despite having a diagnostic accuracy of only 20%, X-ray mammography is the most commonly used imaging technique employed to detect breast cancer. One of its limitations is that is cannot measure the tissue’s total haemoglobin concentration (HbT) and blood oxygen saturation (SO2), which are potential indicators of cancer.

There is evidence to suggest that breast cancer tumors may have greater oxygen consumption and develop a larger number of blood vessels than normal tissue. As a result, optical techniques that can measure these parameters are attracting a lot of attention.

The P-Scan maps the concentration of HbT and SO2 in human tissue. Its hand-held probe contains an array of eight diode-lasers and eight silicon-based photodiodes. Emitting continuous-wave light at either 690 or 830 nm, the diodes supply 0.15W/cm2 to the surface of the skin. The probe covers a surface area of 2.5 x 2.5 cm and that the light penetrates 2 cm into the tissue.

“The probe is placed at five to eight positions on the breast surface and stays at each position for a few seconds,” said Jimmy Mao, principal scientist at ViOptik . “It takes less than one second to analyze the whole data set collected in a P-Scan examination.”

Mao and co-workers analyze the data using statistical methods. “Complex physiological changes might increase HbT in some surrounding tissue and decrease SO2 in others,” say the authors. “We therefore focus on the statistical properties over all of the 16 pixels.”

The team has now come up with a series of statistical conditions that flag-up if a suspicious area in a mammogram is likely to be cancerous. In a study involving 48 patients, each of which had been recalled for a biopsy after irregular mammogram results, the P-Scan correctly identified 92% of the patients with a cancerous tumor.

“Our company now plans to develop an ultrasound/P-Scan dual modality imaging system and test its performance in a small clinical population having suspect lesions detected with mammography,” Mao told Optics.org.

Author
Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe magazine.

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