The increasing interest in minimally invasive surgery has encouraged the use of more sophisticated medical instruments and computer-assisted interventions. Minimally Invasive Radiofrequency Ablation (RFA) is performed to ablate tumor tissues using a needle-like probe with multiple electrodes. In this paper, a computational algorithm to plan optimal needle trajectories subject to complete tumor coverage is proposed. The algorithm was designed such that it had taken into consideration of the multiple objectives that the tumor ablation aims to achieve. The concepts of sphere covering and genetic algorithm were utilized in the algorithm proposed. The simulation of the preliminary algorithm had also displayed results that met the objectives designed for the algorithm.