BACKGROUND The size of the saccular intracranial aneurysm (IA) has been used as the primary indicator for rupture risk. We investigated at which size IAs that rupture did so, and whether this size has significantly changed over time. METHODS Patients treated for ruptured IAs were identified from the Aneurysm Database of the Tampere University Hospital. The size of the IA at the time of rupture was measured from computed tomographic angiography or digital subtraction angiography made to diagnose the aneurysm. Data for the clinical risk factors for rupture were collected from the patient's medical records. RESULTS Of the 2545 patients with ruptured intracranial aneurysms (IAs) admitted, the size of the ruptured IA could be determined for 76% (1925 of 2545). Fifty‐one percent (984 of 1925) of the studied IAs ruptured at a size <7 mm. Both the mean and the median size of the IA at rupture had a downward trend from 1989 to 1997 (median decrease from 10 mm to 6 mm) but have remained relatively constant since. Forty‐six percent (881 of 1925) of the patients with a ruptured IA were not known to have any lifestyle‐related aneurysmal subarachnoid hemorrhage risk factor. Of the IAs that ruptured small, 35% were located in the anterior communicating artery and 14% in other small intracranial arteries. CONCLUSION Small size should not be used to exclude unruptured IAs from prophylactic treatment. The observation that the size at which IAs rupture has previously decreased, suggesting a change in relative importance of risk factors or characteristics of a contemporary patient population compared with older cohorts.

Lenses are always exposed to radiation in brain computed tomography (CT) scans. However, the lens dose can be reduced by excluding lens from scanning area by optimising gantry tilt and scan length. The object of this study is to retrospectively analyse if the optimisation by gantry tilt and scan length have been adequate in the CT scan of the brain, and to prospectively analyse the effect of radiographer training to the quality of the CT examinations. This study was conducted in two parts. In all, 329 brain CTs performed in the Tampere University Hospital from 2017 to 2019 were revised retrospectively. The prospective part included 51 brain CT studies conducted in October 2021. Dose to the eye of the lens was modelled using CT-Expo using zero-degree beam angle and scan lengths to expose the lens either to the primary or scattered radiation. Non-zero gantry tilt had been used in a large proportion of the CT examinations in the retrospective setting, 84.8%. However, the lenses were successfully excluded from the scan area in only 1.8% of the examinations. In the prospective part, the gantry tilt was used in 98% of the studies and the proportion of successful examinations rose from 1.8 to 11.8%. The lens dose decreased significantly when the eyes were excluded from the imaging area. The modelled lens dose in the large retrospective part was 25.9 mGy (17.8–49.2 mGy) when the eyes were included and 1.5 mGy (0.4–1.9 mGy) when the eyes were excluded. The lens dose was similar in the small prospective part. Despite the gantry tilt is widely used, unnecessary lens irradiation occurs extensively because of suboptimal gantry tilt and scan length. The training of radiographers reduces the radiation exposure to the lens by more optimal gantry tilt and scan length.

In a recent article published in Neurology, Rautalin et al.1 report substantial regional differences and a decreasing trend in the incidence of aneurysmal subarachnoid hemorrhage (aSAH) in all regions of Finland. However, in Tampere University Hospital, one of the referral centers for the population in this article, we do not see the decreasing trend in the number of admitted aSAH cases, but rather a constant variation from 1990 to 2014.2

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