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Numerical Study on a Cooling Strategy for Boiling, Saline-Based Tumor Hyperthermic Injector

Abstract This research proposes a cooling strategy for a percutaneous hyperthermic needle through injecting boiling water or physiological saline solution into a deep regional tumor for treatment purpose. To avoid scalding the surrounding normal tissues along the insertion path of the needle, a cooling gas film was introduced as a barrier to prevent heat transfer from the hot medium. The structure of the injector resembles that of the clinically used syringe. However, its injector head consists of two concentric thin-walled tubes. Through the inner tube, the high-temperature fluid can be transferred and injected into the target tumor site. At the space between the external and the inner tubes, cooling fluids such as air, water, and nitrogen gas can be forced to run along the tube. In this way, the temperature on the outer wall of the injector will be lowered and well controlled within an acceptable, safe range, protecting the normal tissues from thermal injury. Heat transfer models for the five regions—the inner tube, the outer tube, the surrounding tissues, the cooling fluid, and the hot medium—are established. Numerical calculations are performed to test whether the incorporated cooling fluid can prevent the tissues from thermal injury while allowing high temperature fluid to be injected into the target tumor site. The obtained results demonstrate the feasibility of using a thin film gas to cool the wall of the injector. Effects of the temperature jump or velocity slip in the cooling gas were also studied.