Realization and Quality Improvement of the Ultrasonic Diffraction Tomography for Medical Diagnosis

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Aiming at the realization of the ultrasonic diffraction tomography, strategies for reducing the artifact of the image were presented as follows.1 Reduction of Errors in Input Data (1) High Resolution Measurement of the Complex Scattered Wave Amplitude by Using the Digital Synchronous Detection Method : Scattered signal amplitudes were measured by the combination of the selective sampling of the received rf burst signal and the digital synchronous detection calculation. This method has an advantage that the signal component by an ideal plane wave illumination can be extracted keeping high noise tolerant capability.2 Error Reduction in Reconstruction Procedure (1) Smoothing Filtering : Validity of the smoothing filter for the mitigation of noise amplification in the reconstruction calculations was demonstrated.3 Mitigation of the Scattering Model Error (1) Optimization of the Surrounding Medium Velocity : Contrary requirements for minimizing the errors caused by the weak scattering appro … More ximation and the measurement data noise were satisfied by adjusting the surrounding medium velocity at optimun value. (2) Using the Knowledge of the Background Velocity : For the relaxation of the weak scattering condition, the background informations were incorporated into the conventional first-order Born reconstruction based on the knowledge of the background velocity information. (3) Two-Dimensional Model Error : From the simulation calculation using the three-dimensional sphere object, it was shown that optimum object velocity exits which makes the model error to be minimum.4 Performance Examination Quantitative precision of the reconstructed velocity image was verified through the simulation and experiment examinations using the concentric cylinder tissue mimicking object. It was verified that images could be obtained with high fidelity witin the tolerances of practical situations. Hereafter, practical examinations for the breast cancer screening test, incorporation of the three-dimensional reconstructing scheme are necessary. Less