Automated Non-invasive Analysis of Motile Sperms Using Cross-scale Guidance Network

Unbiased measurement of sperm morphometric and motility parameters is essential for assessing fertility potential and guiding visual feedback for microrobotic manipulation. Automated analysis of multiple sperms and selection of an optimal sperm is crucial for in vitro fertilisation treatment such as robotic intracytoplasmic sperm injection. However, conventional image processing methods have limitations in analysing small sperm objects under microscopic imaging. The emergence of convolutional neural networks (CNNs) has offered promising advancements in microscopic image analysis. However, previous CNN methods have struggled to accurately segment tiny objects, requiring staining or fluorescence techniques to enhance visual contrast between sperm and culture medium, leading to clinical impracticality. To address these limitations, we introduce a novel segmentation network named the cross-scale guidance (CSG) network for accurate and efficient segmentation of minute sperm objects. The CSG network employs innovative modules, including collateral multi-scale convolution, cross-scale feature map guide, and multi-scale feature fusion, to preserve essential sperm details despite their small size. Experimental results indicate that the CSG network surpassed the state-of-the-art models designed for small object segmentation, achieving a significant increase up to 18.62% higher mean intersection over union (mIoU). Additionally, the CSG network excelled in sperm morphometric analysis, achieving errors below 20%. Moreover, sperm motility parameters were further derived from the segmentation results for comprehensive sperm fertility analysis.