To test the capability of the proposed antenna for heating the interstitial tumors, the size, shape, and location of the tumor were changed. The models were varied from a very simple model without a tumor and blood vessels to complex models that contain realistic tumors and blood vessels. The antenna was tested in six different 3D liver models. A floating sleeve antenna with 0.5 w input power was designed to resonate at 2.45 GHz. This study aims to design, model, and simulate a microwave sleeve antenna for hepatic (liver) hyperthermia. Microwave hyperthermia is a treatment modality that uses microwaves to destroy cancer cells by increasing their temperature to 41–45 ☌.