Pulsed Imaging Through Biological Tissue by Nonlinear Optics

Nolinear optical imaging is proposed for in-vivo detection and imaging through biological tissue. A major application is clinical optical mammographic screening for breast cancer. Unlike conventional x-ray mammography, the proposed optical imaging technique utilizes visible radiation. Since this non-ionizing radiation poses no risk of radiation-induced carcinoma, nolinear optical breast-cancer screening examinations can be repeated periodically with no risk to the patient-a revolutionary development. This advance would be valuable to both civilian and military hospitals. The technology is alos applicable to underwater imaging, which is of interest to the Navy. Nonlinear optical imaging utilizes a single low-peak-power repetitively pulsed light source. The presence of lesions, whose absorption and/or scattering properties differ from those of the sorrounding tissue, can be determined from observation of the light transmitted through the tissue. The technique relies on nonlinear optics in specific media that function under extremely low light-power conditions and can operate in a relatively compact geometry. These nonlinear optical media provide high spatial resolution by temporally gating and amplifying light that has undergone minimum scattering, thereby discriminating against highly scattered light. The goal is an optical scan of duration 1 sec to detect submillimeter-size lesions in a 40 mm thic breast. Phase I is a theoretical effort to assess the feasibility of the technique and design a Phase II proof-of-principle laboratory demonstration. Anticipated Benefits: The major application of a nonlinear-optics imaging system is rapid, safe optical mammography suitable for clinical screening for breast cancer. Unlike a conventional x-ray mammogram, a nonlinear optical scan poses no risk of radiation-induced cancer. With an estimated US market of tens of millions of examinations per year, its widespread commercial application is assured. The technology that will be developed also has other applications, including underwater imaging.