01 July 2026

Every practitioner understands the imperative of precise dosage and the delicate balancing act of too little versus too much, especially when using modalities like Computerised Tomography (CT).

Accounting for operator, anatomical and behavioural variability, however, only complicates this calculation for CT ranging leading to what we know as "CT Over-scanning" where scan ranges are extended beyond anatomical boundaries to little or no benefit.

Over-scanning in CT is not a new phenomena, but an internationally authored paper published in the Journal of Medical Radiation Sciences (JMRS) highlights new technologies and training - that could help clinicians undertake more confident calculations.

In a review of 38 international studies from 2010 to 2025 of varying CT protocols, authors discovered a substantial variation in definitions of "Over-scanning”, despite an almost universal reporting of scans taken beyond anatomical boundaries – particularly in CT-KUB and paediatric abdominopelvic imaging to negligible benefit.

Researchers reported over-scanning ranging from approximately 12 mm to 90 mm, with prevalence ranging from 13% to 100% across protocols.

“This recurring pattern of substantial excess coverage indicates that current planning practices often prioritise avoidance of under-scanning over adherence to anatomical boundaries” writes Bani-Ahmed et all.

“While clinically justified, this approach still increases radiation exposure and highlights the need to balance diagnostic caution with optimised scan range selection.”

“Over-scanning in CT is a common and avoidable contributor to unnecessary radiation exposure.”

“Implementing these measures consistently across institutions is essential to achieve sustainable radiation dose optimisation and promote best practice in CT imaging."

In contrast to over-scanning in CT, Under-scanning poses a risk to expose the patient to a repeated round of imaging and subsequent radiation dose if the scan range fails to represent the full anatomy; which understandably creates caution for clinicians when calculating scan ranges.

Analysing contributions to over-scanning, authors attributed these results across four main ‘levels’: Patient, System, Operator and Protocol, with the Protocol and Operator level accounting for over 70% of Over-scanning contributions, citing anatomical and pathological variation and caution in scan planning as dominant contributing factors.

Across each level, authors highlighted modern mitigation strategies such as the integration of AI-assisted scan range planning tools in tandem with additional radiographer education that could, and have been, used to give practitioners greater confidence in scan range planning.

You can read the published paper, all author recommendations and more available online for free, through ASMIRT and NZMIRT’s Journal of Medical Radiation Sciences.