A method and device for determining the flow rate of the wet gas using real-time THz imaging and for determining the flow rate of solid contaminants in oil and gas pipelines using real-time Tera Hertz (THz) imaging is disclosed. A THz imaging device for real-time multiphase flow measurement comprises a THz imaging subsystem having a THz source and an imaging capturing a captured image. Wherein the imaging having at least a two dimensional array of pixels, wherein the multiphase flow may comprise at least one of oil, water, gas and solid contaminants. Further, a method for real-time measurement of a wet gas flow of a gas is disclosed. The flow of gas comprising at least one of a fluid phase or solid contaminants in the gas flow. The method comprises at least the steps of using a THz subsystem on the gas flow to acquire a captured image and further processing the captured image to determine the flow rate of the flow of gas.