Interventional neuroradiology procedures have expanded over the past decade alongside technological development and rising clinical demand. These procedures often involve higher radiation doses and longer exposure times than many other imaging examinations, making dose management a central concern. Diagnostic reference levels support radiation protection by providing benchmarks for typical exposure levels, yet differences in how they are defined, measured and reported limit comparison between centres and countries. A recent scoping review in European Radiology compiles reported values for key neuroradiology procedures and shows substantial variation across dose metrics, procedures and methodologies. It also highlights how differences in percentile selection, grouping of procedures and data collection approaches affect consistency in benchmarking.
Variation in Reported Dose Metrics
Diagnostic reference levels are reported for several core interventional neuroradiology procedures, including cerebral angiography, stroke thrombectomy, aneurysm coiling and arteriovenous malformation or fistula embolisation. Across these procedures, three primary dose metrics are consistently used: air kerma–area product, fluoroscopy time and reference air kerma.
Reported values show wide ranges across all procedures. For cerebral angiography, air kerma–area product ranges from 41 to over 250 Gycm², while fluoroscopy time varies from a few minutes to nearly half an hour, and reference air kerma spans several hundred milligray. Stroke thrombectomy procedures display higher exposure levels overall, with fluoroscopy times extending up to around 45 minutes and reference air kerma exceeding 1500 mGy in some cases.
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Aneurysm coiling and embolisation procedures show even broader variability. Air kerma–area product values can approach 500 Gycm², and fluoroscopy times extend well beyond one hour in complex cases. Reference air kerma values in these procedures reach several thousand milligray. Embolisation procedures demonstrate the highest exposure ranges among all categories.
Most reported diagnostic reference levels are defined using the 75th percentile of dose distributions. However, variations in percentile selection, grouping of procedures and inclusion criteria contribute to inconsistencies. Differences in sample sizes and data collection approaches further widen the range of reported values, limiting direct comparison between centres.
Methodological Inconsistencies Across Studies
The review identifies substantial heterogeneity in how diagnostic reference levels are established. Studies vary in design, with both prospective and retrospective approaches represented, and sample sizes ranging widely. Some datasets are derived from national surveys, while others rely on single-centre observations.
Differences in methodology extend to the selection of dose indices. Some datasets report only air kerma–area product, while others include additional metrics such as fluoroscopy time and reference air kerma. This variation restricts the ability to compare results across studies or to establish consistent benchmarks.
Procedural classification also differs. Some datasets treat procedures as single categories, while others subdivide them based on complexity or clinical characteristics. In certain cases, procedures are stratified into multiple subgroups, which complicates comparison with datasets that present aggregated values.
Statistical approaches used to derive diagnostic reference levels also vary. While many studies rely on percentile-based definitions, differences in calculation methods and analytical techniques introduce additional variability. Heterogeneity in data collection protocols, including equipment settings and measurement techniques, further contributes to inconsistent results.
National diagnostic reference levels reflect local clinical practice, patient populations and equipment configurations. As a result, differences between countries may arise from methodological divergence rather than genuine variation in clinical performance. Without alignment in parameter selection and reporting standards, comparisons remain limited.
Factors Influencing Radiation Dose
Several factors influence radiation dose in interventional neuroradiology procedures. Procedure complexity plays a central role. More complex interventions typically require longer fluoroscopy times and higher radiation exposure. Dose metrics indicate a progression from lower values in diagnostic angiography to higher values in aneurysm coiling and embolisation procedures, reflecting increasing procedural difficulty.
Patient-related factors also contribute to dose variation. While gender does not significantly affect radiation exposure in cerebral angiography, anatomical characteristics and access routes can influence dose levels. For example, procedures involving catheter navigation through larger body regions may result in increased exposure due to patient thickness and anatomical variation.
Equipment type and technological evolution affect radiation delivery. Older systems using image intensifiers may require higher exposure levels to maintain image quality, whereas newer systems equipped with flat panel detectors and pulsed fluoroscopy support dose reduction. Improvements in hardware and software, along with enhanced image processing capabilities, contribute to gradual reductions in reported dose values over time.
Imaging techniques and procedural protocols introduce further variability. Differences in frame rates, number of projections and exposure settings can significantly alter radiation dose. Automated exposure control systems and variations in operator practice influence fluoroscopy time and dose accumulation.
Dose reduction technologies, such as roadmap fluoroscopy and optimised frame rates, enable lower radiation exposure while maintaining image quality. Operator expertise and experience also affect procedural efficiency and radiation management, contributing to differences observed between centres.
Diagnostic reference levels in interventional neuroradiology vary widely across procedures, centres and methodologies. Differences in dose metrics, procedural classification and data collection approaches limit comparability and benchmarking. Variability reflects both clinical complexity and methodological inconsistency. Greater alignment in how diagnostic reference levels are defined, measured and reported would support more reliable comparisons and improved dose optimisation. Standardised approaches across institutions and countries would strengthen radiation protection practices and enable more consistent monitoring of patient exposure in interventional neuroradiology.
Source: European Radiology
Image Credit: iStock
References:
Grech M, Zarb F, Grech R et al. (2026) Diagnostic reference levels in interventional neuroradiology: a scoping review. Eur Radiol: In Press.
