Corrigendum: Radioactivity and space range of ultra-low-activity for in vivo off-line PET verification of proton and carbon ion beam—a phantom study - Zhang, Fuquan; Zhang, Junyu; Lu, Yan; Sheng, Yixiangzi; Sun, Yun; Zhang, Jiangang; Cheng, Jingyi; Zhou, Rong (Frontiers in Public Health, 2024)