Dose Mapping Using Image Registration for Reirradiation: A Systematic Review

As reirradiation becomes increasingly common due to longer patient survival, accurately mapping previous radiation dose is essential to balance toxicity and tumour control. Image registration (IR) is widely used to align previous dose distributions with current anatomy. However, significant anatomic changes between treatment courses pose unique challenges, and it remains unclear how existing IR practices-largely developed for other contexts-translate to reirradiation. This systematic review aims to report on what is currently being done in the field regarding the use of IR for dose mapping in reirradiation scenarios, identify methodological gaps, and propose recommendations to improve reproducibility and clinical utility. We performed a Preferred Reporting Items for Systematic Reviews and Meta-Analysis-compliant search for full-length articles (PubMed and Scopus) and conference abstracts (ScienceDirect and American Association of Physicists in Medicine, AAPM) that explicitly referenced IR for dose mapping in reirradiation. Each article was reviewed by ≥2 independent reviewers, with key data extracted on IR approaches and evaluation strategies. As of mid-May 2025, 34 articles and 30 abstracts were selected. Most studies lacked comprehensive evaluation: about one-third reported geometric accuracy metrics, and few included dosimetric assessments or uncertainty estimation. Multimodal reirradiation, nonexternal beam techniques, and pediatric populations were notably underrepresented. Based on the synthesis of current literature and expert consensus, we propose 3 clinical and 10 research recommendations to support reproducible research and clinical practices. Clear and consistent reporting of registration methods, geometrical, and dosimetrical assessments are essential to improve the reliability of dose mapping and to support safer, evidence-based use of IR in the reirradiation setting.