3D localization of absorbing lesions by CW whole field diffuse reflectance Imaging.

N. CARBONE; G. BAEZ; M. V. WAKS SERRA; H. GARCÍA; H. O. DI ROCCO; D. I. IRIARTE; J. A. POMARICO; DIRK GROSENICK; RAINER MACDONALD

Ulm

Congreso; International Conference on Laser Applications in Life Science LALS 2014; 2014

Diffuse reflectance from tissue is exploited for near infrared spectroscopy and NIR diffuse optical imaging relevant for biomedical imaging. Because of diffusive photon migration in tissue, imaging of function, as e.g. revealed by biomarkers like oxy- and deoxy-hemoglobin, is more reasonable than structural imaging. In this contribution we introduce a novel non-contact wide-field continuous wave imaging technique based on spatial point spread function measurement employing a CCD-sensor.  Images of a lesion-carrying turbid medium, acquired by a CCD camera under multiple point like CW illumination, have been normalized to a suitable background image to detect an absorbing inclusion and to localize it. Experiments have been carried out with a phantom containing an inclusion with absorption contrast of four and with background optical properties typical for biological tissues. In-plane localization of the inclusion is achieved using two or more of the images. Depth localization is then achieved by analyzing the photon ?banana? between the source point and the center of the lateral image of the lesion. A typical result is shown in the Figure.  We report on investigations of CW diffusely reflected light for a point-like source, registered by a CCD camera imaging a turbid medium with an absorbing lesion. It is shown that detection of lesions with enhanced absorption is achieved if images are normalized properly to background intensity. A theoretical analysis based on the diffusion approximation was done to investigate the sensitivity and the limitations of our proposal and a novel procedure to localize the inclusion in 3D was tested. An analysis of the noise and its influence on the detection limits of our proposal is provided. Experimental results on phantoms are discussed, supporting the approach proposed.