From sensitivity gain to clinical decisions: total-body and long-axial-field-of-view PET/CT for diagnosis and image-based management in oncology and systemic disease.

Total-body (TB) and long-axial-field-of-view (LAFOV) PET/CT systems provide extended axial coverage and substantially higher sensitivity than conventional PET/CT. This structured narrative review evaluates how that sensitivity is translated into dose reduction, shorter acquisition, dynamic or parametric imaging, delayed imaging, and image-based management in oncology and selected systemic diseases. PubMed/MEDLINE, Embase, Scopus, Web of Science Core Collection, and Cochrane Library were searched for January 2015-April 2026, with a separate ClinicalTrials.gov search; the manuscript was appraised using SANRA. Seventy-four full-text publications were assessed, and 55 principal TB/LAFOV publications informed the synthesis. Evidence is strongest for protocol optimisation, including reduced activity and abbreviated acquisition, but many studies rely on retrospective list-mode subsampling or image-quality endpoints. Recent comparative studies provide early diagnostic-accuracy and management-impact signals, although single-centre design, delayed-imaging confounding, incomplete reference standards, and absent outcome data limit inference. Dynamic imaging, immunoPET, paediatric applications, and post-radioembolisation ⁹⁰Y dosimetry remain promising but early. Multicentre validation, cross-platform harmonisation, patient-centred outcomes, workflow studies, and prospective health-economic evaluation are required.