Lower-Extremity CT Angiography: Inter-Hospital Dose Variability and Protocol Optimization in Sudan

Introduction Lower-extremity CT angiography (CTA) is widely used for the evaluation of peripheral arterial disease but is associated with substantial radiation exposure. Even when identical CT scanners are used, variability in protocol design may lead to marked differences in patient dose. Purpose The primary aims of this study are: assess inter-hospital variability in radiation dose for lower-extremity CTA performed on identical 64-slice CT scanners (Aquilion 64; Toshiba Medical Systems, Otawara, Japan), identify protocol-related factors amenable to dose optimization within existing CT system capabilities. Methods This multicentre retrospective observational study included 74 adult patients undergoing clinically indicated lower-extremity CT angiography at four hospitals using identical 64-slice CT scanners (Hospital one: n=15; Hospital two: n=21; Hospital three: n=17; Hospital four: n=21). Radiation dose metrics, including volume CT dose index (CTDI_(vol)) and dose-length product (DLP), were collected for all scan phases performed, including the localizer, bolus-tracking, non-contrast helical phase (when clinically indicated), and contrast-enhanced helical acquisitions. No BMI or weight-based exclusion criteria were applied. Phase-specific and cumulative dose metrics were analyzed in relation to acquisition parameters and scan coverage. Results Mean cumulative DLP ranged from 5333.2 to 7911.6 mGy·cm across centres, corresponding to an approximately 1.5-fold difference. Non-contrast and contrast-enhanced helical phases were the dominant contributors to total radiation exposure, with phase-specific DLP values frequently exceeding 1000 mGy·cm. In centres performing non-contrast imaging, this phase occasionally contributed a higher DLP than the contrast-enhanced phase, indicating that selective omission could reduce cumulative dose. In other centres, elevated CTDI_(vol) during contrast-enhanced and bolus-tracking phases offset dose reductions achieved through shorter scan lengths. Several protocols exceeded published regional and international diagnostic reference levels. Published evidence supports that low-tube-voltage acquisition (70-80 kVp) combined with iterative reconstruction can substantially reduce radiation dose and represents a feasible optimization strategy within current scanner capabilities. Conclusion Radiation dose in lower-extremity CTA is largely determined by protocol design rather than scanner hardware. Strategies including selective non-contrast phase omission, low-tube-voltage acquisition, iterative reconstruction, and optimized bolus-tracking can substantially reduce dose while maintaining diagnostic quality. Harmonized implementation across centres is essential for consistent and meaningful dose reduction.