MEDICAL DIAGNOSIS BY 3-D MICROWAVE INVERSE SCATTERING

A NONINVASIVE MEDICAL DIAGNOSTIC TECHNIQUE BY QUANTITATIVE THREE-DIMENSIONAL IMAGING OF DIELECTRIC PERMITTIVITY IS PLANNED. A DIELECTRIC IMAGE OF A TARGET IS RECONSTRUCTED BY MEASURING THE MICROWAVE SCATTERING FIELD AND UTILIZING A SCATTERING MATRIX INVERSION ALGORITHM. THE IMAGE RESOLUTIONIS EXPECTED TO BE LIMITED ONLY BY SIGNAL-TO-NOISE RATIO AND NOT BY THE WAVELENGTH OR DIFFRACTION. THE MICROWAVE DOSE WILL BE ON THE ORDER OF MICROWATT PER GRAM TO TENS OF MICROWATT PER GRAM, WHICH IS TWO TO THREE ORDERS OF MAGNITUDE BELOW THE SAFETY LEVEL. OWING TO THE SENSITIVITY OF DIELECTRIC PERMITTIVITY WITH RESPECT TO VARIOUS BIOLOGICAL TISSUES, THE SYSTEM WILL, COMPARED TO EXISTING IMAGING DEVICES, PROVIDE HIGHER CONTRAST BETWEEN SOFT TISSUES AND BETWEEN TUMOR AND NORMAL TISSUES. WAVELENGTH PLACES A LIMIT ON RESOLUTION ONLY IN THE CASE WHERE SOME FAR-FIELD APPROXIMATION IS USED FOR THE SCATTERING FIELD. TO OVERCOME THE WAVELENGTH LIMITATION ANDTO RETRIEVE ALL THREE DIMENSIONS OF THE TARGET PROFILE, NEAR-FIELD SCATTERING DATA ARE USED AND A STABILIZING TECHNIQUE IS EMPLOYED TO STABILIZE SCATTERING MATRIX INVERSION. TIME-CONSUMING COMPUTATION OF SCATTERING MATRIX AND MATRIX INVERSION MAY BE PERFORMED OFFLINE AND ONCE AND FOR ALL. IMAGING PROCESSING TIME WILL BE SUBMILLISECOND, SO REAL-TIME IMAGING OF PHYSIOLOGICAL FUNCTIONS MAY BE ACHIEVED.