MICROWAVE IMAGING FOR TISSUE ASSESSMENT - INITIAL EVALUATION IN MULTITARGET TISSUE-EQUIVALENT PHANTOMS

A prototype microwave imaging system Is evaluated for its ability to r ecover two-dimensional (2-D) electrical property distributions under t ransverse magnetic (TM) illumination using multitarget tissue equivale nt phantoms, Experiments conducted in a surrounding lossy saline tank demonstrate that simultaneous recovery of both the real and imaginary components of the electrical property distribution is possible using a bsolute imaging procedures over a frequency range of 300-700 MHz, Furt her, image reconstructions of embedded tissue-equivalent targets are f ound to be quantitative not only with respect to geometrical factors s uch as object size and location but also electrical composition, Quant itative assessments based on full-width half-height criteria reveal th at errors in diameter estimates of reconstructed targets are less than 10 mm in all cases, whereas, positioning errors are less than 1 mm in single object experiments but degrade to 4-10 mm when multiple target s are present, Recovery of actual electrical properties is found to be frequency dependent for the real and imaginary components with backgr ound values being typically within 10-20% of their correct size and em bedded object having similar accuracies as a percentage of the electri cal contrast, although errors as high as 50% can occur, The quantitati ve evaluation of imaging performance has revealed potential advantages in a two-tiered receiver antenna configuration whose measured field v alues are more sensitive to target region changes than the typical tom ographic type of approach which uses reception sites around the full t arget region perimeter, This measurement strategy has important implic ations for both the image reconstruction algorithm where there is a pr emium on minimizing problem size without sacrificing image quality and the hardware system design which seeks to economize on the amount of measured data required for quantitative image reconstruction while max imizing its sensitivity to target perturbations.