<title>Effects of sample preparation on the optical properties of breast tissue</title>

Abstract

The optical properties of biological tissue should be determined in vivo whenever possible. However, for those instances when in vivo studies are impractical, too expensive or inappropriate, and when blood flow is not an issue, the ability to perform in vitro studies then becomes invaluable. Optical absorption spectroscopy shows that it may be possible to obtain meaningful information about the optical properties of human breast tissue from in vitro samples if strict preparation and measuring protocols are used. That a strict protocol for storing and handling tissue is critical can be seen from our observations of changes in the optical absorption spectra that occur in response to formalin fixation, the passage of time, application of stains and dyes, and storage in growth medium of the excised tissue. In vivo optical absorption spectroscopy measurements have been made on human breast cancer xenografts and compared with in vitro measurements on breast biopsies prepared according to precise collection and treatment protocols. There is a 'window of opportunity' before time dependent changes in the UV optical absorption spectra of the excised tissue specimens occur. This time window of opportunity widens at longer wavelengths with the least changes occurring in the optical spectra in the NIR.