Three-dimensional Positioning of the Micropipette for Intracytoplasmic Sperm Injection

ICSI (Intracytoplasmic sperm injection) is one of the most effective treatments for severe male infertility. During the implementation of the ICSI, it is necessary to perform the three-dimensional positioning of the tip of the glass injection micropipette. At present, the process is mainly controlled by skilled operators. Such manual operation is time-consuming and likely to cause micropipette damage or even serious damage to the oocyte membrane due to the inaccurate positioning. In this paper, an automatic system was developed for micropipette positioning. The microscopic positioning is carried out by autofocusing and planar positioning. A search strategy based on Dynamic Curve Fitting (DCF) was proposed to avoid local extremum issues due to the noises during the autofocusing. The proposed search strategy is adaptive to different focus algorisms, making the design of autofocusing becomes simpler. Besides, we proposed a planar positioning algorithm that can quickly and accurately obtain the tip position of the micropipette at the focusing plane. Finally, the visual servo control is employed to move the micropipette to the center of the vision. The experimental results demonstrated that the DCF method can accurately (mean error: 3 μm) find the focusing plane when applying random Gaussian noise with a mean value of 0 and a variance of 1 to the focus measure. By contrast, both the hill-climbing search method and the Fibonacci search method cannot work properly. The tip positioning algorithm provides a real-time in-plane tip positioning at a frame rate of 40 Hz with an average accuracy of 11 μm.