Dose reference levels and clinical determinants in stroke neuroradiology interventions

To establish dose reference levels (RLs) for stroke interventions while carefully analysing the impact of clinical and technical parameters on patient exposure.

The study retrospectively analysed data from 377 stroke patients prospectively collected between 15 October 2015 and 30 March 2017 at a single, level-3 stroke centre equipped with Philips Allura Clarity systems. Local dose RLs were first derived as the 75th percentile of the dose area product (DAP), cumulative air kerma (K_a,r), fluoroscopy time (FT) and the number of images (NI). Univariate and multivariate negative binomial regressions were considered for the statistical analysis to investigate the dose variability with clinical and technical parameters such as patient's age and sex, occlusion removal technique, number of passages, single-plane or biplane equipment, etc. RESULTS: Local stroke dose RLs were derived in terms of total DAP (162 Gy cm²), K_a,r (854 mGy), FT (42 min) and NI (559). Gender (relative dose multiplier (RDM) 1.31; 95% CI 1.12-1.45), number of passages (RDM 1.22 per passage; 95% CI 1.10-1.22) and procedure success (RDM 0.52, 95% CI 0.55-0.80) proved to be key parameters affecting patient dose. Meanwhile the statistical analysis did not find any difference in relative dose received by patients owing to age, baseline NIHSS score, occlusion removal technique, posterior circulation, support of an anaesthesiologist or use of biplane equipment.

Stroke dose RLs introduced in this work promote the optimisation of patient doses. Male gender, number of passages and success of recanalisation are independent key parameters affecting patient dose.

• Stroke dose RLs derived in terms of total DAP (162 Gy cm ² ), K _a,r (854 mGy), FT (42 min) and NI (559) will help optimise the radiation safety of patients treated with mechanical thrombectomy. • Male gender (relative dose multiplier 1.31; 95% CI 1.12-1.45), number of passages (RDM 1.22 per passage; 95% CI 1.10-1.22) and success of recanalisation TICI score > 2b (RDM 0.52, 95% CI 0.55-0.80) are independent key parameters affecting patient dose. • Stent retriever or aspiration technique showed no significant difference in terms of the dose delivered to the patient; neither technique should be favoured for dosimetric reasons provided that there is no difference regarding clinical outcomes.