The possibility of quantitative phase tomography of dielectric objects in matching media is investigated. Computed cross sections of homogeneous and concentric cylinders with complex permittivity are generated from exact analytic expressions for scattered fields. The effect of dielectric loss within the object medium on the validity of the first-order Born approximation is examined. A technique for accurate measurement of weak scattering in the presence of a strong incident field is presented. The subtraction of distortion effects in the reconstructed phase image provides a means for microwave metrology of internal loss distributions within dielectric bodies.