FREQUENCY-DOMAIN OPTICAL MAMMOGRAPHY - EDGE EFFECT CORRECTIONS

We have investigated the problem of edge effects in laser-beam transil lumination scanning of the human breast. Edge effects arise from tissu e thickness variability along the scanned area, and from lateral photo n losses through the sides of the breast. Edge effects can be effectiv ely corrected in frequency-domain measurements by employing a two-step procedure: (1) use of the phase information to calculate an effective tissue thickness for each pixel location; (2) application of the know ledge of tissue thickness to calculate an edge-corrected optical image from the ac signal image. The measurements were conducted with a ligh t mammography apparatus (LIMA) designed for feasibility tests in the c linical environment. Operating in the frequency-domain (110 MHz), this instrument performs a transillumination optical scan at two wavelengt hs (685 and 825 nm). We applied the proposed two-step procedure to dat a from breast phantoms and from human breasts. The processed images pr ovide higher contrast and detectability in optical mammography with re spect to raw data breast images. (C) 1996 American Association of Phys icists in Medicine.