Résumé:
The DORT method (French acronym for diagonalization of the time reversal operator) is derived from the theory of iterative time reversal mirroring. It consists of a singular value decomposition of the time reversal operator obtained through single element transmissions and receptions. The number of eigenvalues relates to the number of bright point scatterers in the medium, and each eigenvector is the transmit signals that focuses on each bright scatterer. However, the signal-to-noise ratio (SNR) resulting from a single element transmit is low, which negatively impacts the sensitivity of the DORT method. This work consists of an adaptation of the DORT method to an imaging mode. Focused transmissions in the medium are used and a windowing preprocessing operation on the received signals significantly increases the sensitivity. The more robust behavior of this modified DORT method is tested on Field II simulated data and then on a phantom made of strings of different material embedded in speckle. Data on freshly excised breast surgical samples containing microcalcifications were processed and every microcalcifications was detected. Finally, results on in vivo acquisitions prove that the technique can accurately detect and locate microcalcifications in nonhomogeneous media with aberration.

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