The use of entangled-photon imaging in optical biopsy: a feasibility study

We examine a novel diagnostic method suitable for optical biopsy, i.e., the noninvasive in vivo detection of malignant lesions in human tissue. Entangled-photon imaging is an emerging technology based upon the use of non-classical sources of light such as optical parametric oscillators (OPO). These sources generate above-threshold signal and idler beams that have intensity fluctuations highly correlated in space and time (twin beams)(1,2). It has been shown that low-intensity OPO's make possible high sensitivity absorption measurements of weak targets, below the shot-noise limit(3,4). The direct use of this technology for optical biopsy is severely restricted by the large amount of scattering noise associated with light-tissue interaction. We report what is, to our knowledge, the first feasibility study on a differential wavelength, OPO-based setup targeted for mammography. Constraints related to the entanglement time, OPO selection and background suppression are analyzed. The paper concludes with a review of future developments and challenges.