Our paper has been accepted and is now available online in Knowledge-Based Systems: Phan Tai Duc; Nhut Minh Nguyen; Khang Phuc Nguyen; Phuong-Nam Tran; Nhat Truong Pham; Linh Le; Choong Seon Hong; Duc Ngoc Minh Dang, From object difficulty to image scoring: A strategy for active learning in object detection, 2026. This work proposes a novel strategy to improve active learning in object detection by effectively aggregating object-level difficulty into image-level scoring.