This paper presents a research that aims at developing a system for microwave imaging and hyperthermia ablation of brain tumors. The system depends on a MIMO array of microstrip antennas to be mounted on the head. An L-band antenna is designed to increase the power radiated toward the human and increase the SAR values in the tumor. The size reduction is achieved by adding a high dielectric layer just above the antenna. The antenna is made of a short-circuited- slotted triangle on a thick foam substrate to enhance the bandwidth. A directional coupler is designed for use in exciting the antenna and collecting the reflected signal. This allows the achievement of imaging and hyperthermia treatment functionality, simultaneously. S-parameters are monitored of four antennas installed on a tank filled with a brain simulating liquid in the presence and absence of an anomaly. Results are presented of the simulations and the experimental measurements.