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  • Diagnosis through light, not the needle

Sep 2010
Marie Freebody,

STORRS, Conn. – Radiologists one day could have an IR-based diagnostic tool integrated into traditional ultrasound systems that could lower the rate at which women must undergo breast biopsies for suspicious lesions.

The noninvasive alternative to conventional needle biopsies is based on an emerging imaging technique – diffuse optical tomography – combined with ultrasound localization. In a study involving 178 women, Dr. Quing Zhu, a professor of bioengineering at the University of Connecticut, and her collaborators found that the two techniques can be used as an adjunct to diagnostic ultrasound for distinguishing early-stage invasive breast cancers from benign lesions.

Today, when mammography and ultrasound cannot determine whether a suspicious breast lesion is malignant or benign, physicians typically recommend a needle biopsy to extract samples of the suspicious tissue for laboratory testing. In current clinical practice, the majority of biopsies performed reveal benign lesions, leading to unnecessary anxiety for women.

Dr. Quing Zhu is shown with a patient in a radiology exam room at the University of Connecticut. The commercial ultrasound machine can be seen on the left. On the right is the near-IR imager designed and built by Zhu’s team. Courtesy of Dr. Zhu.

“The large number of biopsies performed for benign breast abnormalities has long been recognized as a serious problem,” Zhu said. “Optical tomography offers complementary functional parameters, such as tumor angiogenesis [proliferation of blood vessels] and hypoxia [lack of oxygen], when compared to conventional x-ray and ultrasound imaging techniques, and therefore has significant potential to assist the characterization of benign and malignant processes and reduce unnecessary, normal biopsies.”

Dead giveaway

A rapidly growing tumor gives itself away: It has many more blood vessels than normal tissue and rapidly outgrows its blood supply, leaving portions of the tumor with regions where the oxygen concentration is significantly lower than in healthy tissue.

Diffuse optical tomography can measure light absorption within tissue to quantify blood content (hemoglobin level) and blood oxygen levels and, hence, help distinguish malignant from benign lesions.

In Zhu’s study, published in Radiology online in June 2010 and in the print edition in August, the investigators used ultrasound to locate the suspicious lesion, then performed diffuse optical tomography by shining IR light into the area and measuring light absorption at two optical wavelengths.

They computed total hemoglobin levels from the light absorption measured at optical wavelengths of 780 and 830 nm and correlated the measurements with biopsy results. Laboratory examination of tissue samples revealed two in situ carcinomas, 35 carcinomas measuring less than 2 cm, 24 carcinomas measuring more than 2 cm and 114 benign lesions.

“Our next logical step is to work with ultrasound manufacturers to incorporate the light imager into commercial ultrasound units for conducting prospective clinical trials at multiple hospital sites,” Zhu said.

The study of radioactive substances and high-energy radiations such as x-rays and g-rays.
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