Changes in radiological imaging frequencies in children before and after the accident at the Fukushima Daiichi Nuclear Power Plant in Fukushima Prefecture, Japan.

PURPOSE: The accident at the Fukushima Daiichi Nuclear Power Plant has raised concerns about radiation exposure, including medical radiation exposure such as X-ray and CT, in residents of Fukushima. MATERIALS AND METHODS: We compared the numbers and the ratio of outpatients less than 10 years old who underwent imaging examinations [e.g., CT, X-ray, MRI, ultrasonography (US), etc.] at Fukushima Medical University hospital in Fukushima, Japan before (April 1, 2008-March 31, 2011) and after (April 1, 2011-March 31, 2014) the accident. RESULTS: The number of outpatients less than 10 years old decreased after the accident. The number of outpatients less than 10 years old who underwent CT and X-ray examinations also significantly decreased after the accident (p < 0.001, p < 0.01, respectively). CONCLUSION: Our results suggest that the number of pediatric radiological examinations decreased after the accident in Fukushima. We should continue to communicate with patients and their families to ensure that they understand the risks and benefits of radiological imaging in order to overcome their concerns about the nuclear disaster.

A strategy for a rapid radiological screening survey in large scale radiation accidents: a lesson from an individual survey after the Fukushima Daiichi nuclear power plant accidents.

To establish a strategy for a rapid screening survey of surface contamination among a large number of people after nuclear power plant (NPP) accidents, the authors analyzed the measured surface contamination of subjects. From 12 March through 25 March 2011, a screening survey was conducted in a hospital on 336 subjects who had stayed within a 50-km radius of the Fukushima Daiichi NPPs. The count rates from measuring points of each subject were measured and compared in association with individual characteristics such as survey timing, gender, age, and distance between their location and the Fukushima Daiichi NPPs. The count rates from the head, hands, and clothes of subjects were correlated to the survey timing and distance by multiple regression analyses. When subjects were divided into two-by-two groups of survey timing and distance, the count rates from hands were not significantly different from those of the head and clothes. However, the count rates from the shoes of the subjects, excluding one group, were significantly higher than those of the other points. In addition, the count rate from a married couple showed a significant correlation. These findings suggest that measurement of at least two regions, such as one hand and one shoe, can be used as representative survey data in order to save surveillance time for a large number of people.

Quantification of subarachnoid hemorrhage by three-dimensional computed tomography: correlation between hematoma volume and symptomatic vasospasm.

Subarachnoid hemorrhage (SAH) volume was measured by three-dimensional computed tomography (3D-CT) and the correlation examined between the SAH volume and the occurrence of symptomatic vasospasm (SVS). Experimental (in vitro) hematomas were made with blood obtained from 10 volunteers. The hematoma volume was determined by actual measurements and by 3D-CT using a CT number in the range of 40-80 Hounsfield units (HU) on days 1, 4, 7, 11, and 14. The coefficients on days 1 and 4 were relatively high and the correlation between measured and estimated volumes was significant on days 7, 11, and 14. 3D-CT was also performed in 50 patients with SAH at onset (day 0) and on days 1, 4, 7, and 14. The hematoma volume including the volume of normal structures was automatically calculated (V1). The volume of normal structures (V2) with CT numbers of 40-80 HU was calculated in another 50 patients without intracranial lesions as 12 ml. The total hematoma volume was defined as V1 minus mean V2. The mean SAH volume was 44, 36, 21, 11, and 8 ml on days 0, 1, 4, 7, and 14, respectively. The hematoma volumes were significantly larger in patients with SVS than in patients without SVS at all time points. The minimum hematoma volume in patients with SVS was 92, 76, 42, 24, and 12 ml on days 0, 1, 4, 7, and 14, respectively. This method allows the quantitative determination of SAH volume based on 3D-CT, and may be useful in clinical studies of cerebral vasospasm.