Mapping the Landscape of Over-Scanning in CT Imaging: A Scoping Review

INTRODUCTION: Over-scanning in CT refers to extending the scan range beyond intended anatomical boundaries, resulting in unnecessary ionising radiation exposure. Despite its frequent occurrence, it remains poorly defined and inadequately addressed within the radiological community. This scoping review examines the extent of over-scanning in CT imaging, including its definitions, assessment methods, contributing factors and mitigation strategies.

METHODS: A scoping review was conducted in accordance with PRISMA-ScR guidelines. PubMed, Embase, Ovid and Scopus were searched for studies published between January 2010 and December 2025. Extracted data included definitions, assessment methods, prevalence, dose implications, contributing factors and mitigation strategies.

RESULTS: Thirty-eight studies covering brain, chest, abdominal and multi-region CT protocols were included. Over-scanning was prevalent, averaging 75% (range 13%-100%), with excess coverage from 12 mm to about 90 mm, exceeding recommended anatomical margins. Associated effective dose increases ranged from 0.03 to 3.4 mSv, with organ-specific doses markedly higher in paediatric imaging and radiosensitive organs (thyroid, lungs, breasts, testes), amplifying long-term cancer risk. Directional patterns (superior/inferior) varied by protocol, influenced by anatomical complexity, scout-image limitations and radiographer caution to avoid under-coverage.

CONCLUSION: Over-scanning in CT is a multifactorial issue driven by technical, operator, patient and system-level factors. Mitigation requires standardised protocols, radiographer training, education on over-irradiation risks, optimised scout image utilisation and technological support. Key strategies include consistent osseous landmarks, lateral scout views and AI-based planning tools, which offer promising solutions for automating scan range planning, detecting and reducing over-scanning through real-time monitoring and retrospective analysis and enhancing patient radiation safety.