Isolation and habitat analysis of Balamuthia mandrillaris from soil.

Balamuthia mandrillaris is a free-living amoeba that causes meningoencephalitis in mammals. Over 200 cases of infection were reported worldwide, with a fatality rate of over 95%. A clear route of infection was unknown for a long time until a girl died of granulomatous amoebic encephalitis (GAE) in California, USA, in 2003 due to infection with B. mandrillaris detected in a potted plant. Since then, epidemiological studies were conducted worldwide to detect B. mandrillaris in soil and other environmental samples. We previously reported the isolation of B. mandrillaris from the soil in Japan; however, the existing B. mandrillaris culture method with BM3 medium and COS-7 cells was unsuccessful. Therefore, in this study, we aimed to conduct soil analysis to determine the growth conditions of B. mandrillaris. B. mandrillaris-positive soils were defined as soils from which B. mandrillaris was isolated and environmental DNA was PCR-positive. Soils inhabited by B. mandrillaris were alkaline, with high electrical conductivity and characteristics of nutrient-rich soils of loam and clay loam. The results of this study suggest a possible reason for the high prevalence of GAE caused by B. mandrillaris among individuals employed in agriculture-related occupations.

Development of an Automatic Chronological Record Creation System Using Voice AI to Facilitate Information Aggregation and Sharing in the Event of a Disaster.

OBJECTIVE: In the event of a disaster, the chain of command and communication of each relevant agency is important. In this study, a chronological record creation system using voice AI (V-CRS) was developed, and an experiment was conducted to determine whether the obtained information could be quickly and easily summarized in chronological order. METHODS: After a lecture by Japanese Disaster Medical Assistant (DMAT) Team members and 8 medical clerks on how to use the developed tool, a comparison experiment was conducted between manual input and V-CRS utilization of the time to compile disaster information. RESULTS: Results proved that V-CRS can collect information gathered at headquarters more quickly than handwriting. It was also suggested that even medical clerks who have never been trained to record information during disasters could record information at the same speed as trained DMAT personnel. CONCLUSION: V-CRS can transcribe audio information even in situations where technical terms and physical units must be recorded, such as radiation disasters. It has been proven that anyone can quickly organize information using this method, to some extent.

Are Online Simulations for Radiation Emergency Medical Preparedness Less Effective in Teaching Than Face-to-Face Simulations?

OBJECTIVE: The study clarified differences in understanding and satisfaction between face-to-face and online training on radiation emergency medical preparedness (REMP) training. METHODS: The training was held at Hirosaki University between 2018 and 2022, with 46 face-to-face participants and 25 online participants. RESULTS: Face-to-face training was significantly more understandable than online for the use of the Geiger counter (P < 0.05), but the educational effect of virtual reality (VR) was not significantly different from the actual practice. For the team exercise of taking care of the victims, online resulted in a significantly higher understanding (P < 0.05). CONCLUSIONS: Interactive exercises can be done online with equipment sent to learners, and VR is also as effective. The use of videos was more effective for first-timers to learn the practical process from a bird's-eye view, especially for team-based medical procedures.

Training of Medical Responders to Nuclear Disaster: Hybrid Program in the COVID-19 Pandemic.

OBJECTIVE: The spread of COVID-19 has made it difficult to provide training in medical treatment in a radiation disaster. In this study, we will examine the effects and challenges of using a hybrid approach that combines online and face-to-face components. METHODS: A total of 5 face-to face and 25 online medical staff participated in the training program. This program was conducted by using multiple cameras for live coverage, while protective clothing and decontamination kits had been sent in advance to the participants so that they could experience face-to-face and online learning at the same time. RESULTS: Participants reported a high level of satisfaction and achievement with the style of delivery. They also experienced problems such as fatigue due to long hours, and dissatisfaction with the debriefing. CONCLUSIONS: In designing new online training, it is necessary to consider the quantity and content of the program, and to take participant fatigue into consideration.

222Rn and 226Ra Concentrations in Spring Water and Their Dose Assessment Due to Ingestion Intake.

222Rn and 226Ra concentrations of less than a few to several thousands of Bq L-1 have been observed in several underground bodies of water around the world. Although regulations for these concentrations in water have been implemented internationally, there are currently no regulations in place in Japan. However, concentrations that exceed these internationally recognized regulatory values have also been observed in Japan. In this study, concentrations in spring water in the northern part of Japan were measured and the effective dose from intake of the water was evaluated. 222Rn concentrations were measured using a liquid scintillation counter, and 226Ra concentrations were measured using a high purity germanium detector after chemical preparation. The measured 222Rn concentrations (=12.7 ± 6.1 Bq L-1) and 226Ra concentrations (<0.019-0.022 Bq L-1) did not exceed the reference values set by international and European/American organizations. A conservative estimate of the annual effective ingestion dose of 8 µSv for 222Rn and 226Ra obtained in this study is much smaller than the estimated overall annual effective dose of 2.2 mSv from natural radiation to the Japanese population. However, this dosage accounts for 8% of the WHO individual dosing criteria of 0.1 mSv/year for drinking water.

Estimation of Effect of Radiation Dose Reduction for Internal Exposure by Food Regulations under the Current Criteria for Radionuclides in Foodstuff in Japan Using Monitoring Results.

This study examined the effect of food regulations under the current criteria (e.g., 100 Bq/kg for general foods) established approximately a year after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Foods are monitored to ensure that foods exceeding the standard limit are not distributed; ~300,000 examinations per year have been performed especially since FY2014. This study comprehensively estimated the internal exposure dose resulting from the ingestion of foods containing radioactive cesium using the accumulated monitoring results. Committed effective dose was conservatively calculated as the product of the radioactive concentration randomly sampled from test results, food intake, and dose coefficient. The median, 95th, and 99th percentile of the dose were 0.0479, 0.207, and 10.6 mSv/y, respectively, in the estimation with all test results (without regulation), and 0.0430, 0.0790, and 0.233 mSv/y, respectively, in the estimation with results within the standard limits (with regulation) in FY2012. In FY2016, the dose with and without regulation were similar, except for high percentile, and those doses were significantly smaller than 1 mSv/y, which was adopted as the basis for the current criteria. The food regulation measures implemented in Japan after the FDNPP accident have been beneficial, and food safety against radionuclides has been ensured.

Simulation study on radiation exposure of emergency medical responders from radioactively contaminated patients.

Emergency medical responders (EMRs) who treat victims during a radiation emergency are at risk of radiation exposure. In this study, the exposure dose to EMRs treating hypothetically contaminated patients was estimated using a Monte Carlo simulation, and the findings may be useful for educating EMRs and reducing their anxiety. The Monte Carlo simulation estimated radiation doses for adult computational phantoms based on radioactive contamination conditions and radiation dosages from previous studies. At contamination conditions below the typical upper limit of general Geiger-Müller survey meters, the radiation doses to EMRs were estimated to be less than 1 µSv per hour. In cases with greater contamination due to mishandling of an intense radioactive source (hundreds of GBq), the radiation doses to EMRs could reach approximately 100 mSv per hour. These results imply that a radiological accident with a highly radioactive source could expose EMR to significant radiation that exceeds their dose limit. Thus, authorities and other parties should ensure that EMRs receive appropriate education and training regarding measures that can be taken to protect themselves from the possibility of excessive radiation exposure. The results of this study may provide EMRs with information to take appropriate protective measures, although it is also important that they not hesitate to perform lifesaving measures because of concerns regarding radiation.

Discriminative Measurement of Absorbed Dose Rates in Air from Natural and Artificial Radionuclides in Namie Town, Fukushima Prefecture.

Ten years have elapsed since the accident at the Fukushima Daiichi Nuclear Power Plant in 2011, and the relative contribution of natural radiation is increasing in Fukushima Prefecture due to the reduced dose of artificial radiation. In order to accurately determine the effective dose of exposure to artificial radiation, it is necessary to evaluate the effective dose of natural as well as artificial components. In this study, we measured the gamma-ray pulse-height distribution over the accessible area of Namie Town, Fukushima Prefecture, and evaluated the annual effective dose of external exposure by distinguishing between natural and artificial radionuclides. The estimated median (range) of absorbed dose rates in air from artificial radionuclides as of 1 April 2020, is 133 (67-511) nGy h-1 in the evacuation order cancellation zone, and 1306 (892-2081) nGy h-1 in the difficult-to-return zone. The median annual effective doses of external exposures from natural and artificial radionuclides were found to be 0.19 and 0.40 mSv in the evacuation order cancellation zone, and 0.25 and 3.9 mSv in the difficult-to-return zone. The latest annual effective dose of external exposure discriminated into natural and artificial radionuclides is expected to be utilized for radiation risk communication.

A Simple Survey of the Preparation Situation for Resident's Evacuation in Japanese Prefectures After the Fukushima Daiichi Nuclear Power Plant Accident.

The Japanese government formulated the Nuclear Emergency Response Guidelines in response to the Fukushima Daiichi Nuclear Power Plant accident (FDNPP accident) caused by the Great East Japan Earthquake in March 2011. Under these guidelines, Japan has established its current nuclear disaster response system. This manuscript outlines the transition of Japan's nuclear disaster response system before and after the FDNPP accident and also shows the results of a questionnaire survey on the level of preparation the prefecture currently has for the evacuation of residents at the time of a nuclear disaster. About 70% of the prefectures where nuclear facilities are located or adjacent have completed or are in the process of completing evacuation plans, and all except one indicated they have the equipment needed to perform radiation contamination inspections of residents. These results suggest that activities are taking place throughout Japan to build a new disaster response system. It will be important to verify whether the evacuation manuals prepared by prefectural governments are effective through large-scale training and to develop human resources for performing radiation contamination inspections of evacuating residents.

Assessment of Radiation Dose from the Consumption of Bottled Drinking Water in Japan.

Activity concentrations of 234U, 235U, 238U, 226Ra, 228Ra, 222Rn, 210Po, 210Pb, 40K, 3H, 14C, 134Cs and 137Cs were determined in 20 different Japanese bottled drinking water commercially available in Japan. The origins of the mineral water samples were geographically distributed across different regions of Japan. Activity concentrations above detection limits were measured for the radionuclides 234U, 235U, 238U, 226Ra, 228Ra and 210Po. An average total annual effective dose due to ingestion was estimated for adults, based on the average annual volume of bottled water consumed in Japan in 2019, reported to be 31.7 L/y per capita. The estimated dose was found to be below the recommended World Health Organisation (WHO) guidance level of 0.1 mSv/y for drinking water quality. The most significant contributor to the estimated dose was 228Ra.

THE IMPACT ON THE EYE LENS OF RADIATION EMITTED BY NATURAL RADIONUCLIDES (LEAD-210) PRESENT IN RADIATION PROTECTION GLASSES.

Most radiation protection items made from modern lead contain 210Pb. This study estimated the impact on eye lens of radiation derived from the 210Pb in three types of radiation protection glasses. The counts from the glasses were measured using a Geiger-Müeller survey meter. The net count rate was 92 ± 1 cpm at a distance of 0.5 cm for one type of glasses. Additionally, we conducted a qualitative γ-ray spectrum analysis using a high-purity germanium semiconductor detector. The absorbed dose in the eye lens was related to 210Pb and its daughter radionuclide, 210Bi; this dose was calculated by applying dose conversion coefficients provided by the International Commission on Radiological Protection. The absorbed dose rate in eye lens was conservatively calculated to be on the order of 10 nGy/h for the type of glasses containing the most 210Pb. The dose from ß-rays accounted for >99%. In addition, we investigated the dose-reduction effect using a thin acrylic plate. The count rate approximately decreased to background level by inserting a plate with a thickness of 1 mm. We conclude that the impact of 210Pb contained in radiation protection glasses is negligibly small, particularly considering the usefulness of the significant external exposure reduction.

Time-related study on external exposure dose of 2-deoxy-2-[F-18]fluoro-D-glucose PET for workers' safety.

Time-course study of individual dose equivalents of 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography (18F-FDG PET) was conducted in different hospital workers, and the daily work duties were analyzed. For the measurements, a semiconductor dosimeter was used. The values at intervals of 1 min and 1 h, the monthly cumulative and daily cumulative doses, and trend graphs were acquired with dedicated software and displayed on the reader. The following radiation workers with duties involving maximum external exposure work were included: doctors making diagnoses (4.8 µSv/procedure), nurses removing injection needles (3.1 µSv/procedure), pharmacists performing quality control tests (2.9 µSv/procedure), nuclear medicine technologists assisting patient positioning (6.5 µSv/procedure), and cyclotron engineers performing daily checks (13.4 µSv/procedure). The results of analysis of daily work duties revealed the influencing factors of external exposure dose. To reduce the external exposure dose, investigators should shorten the patient's contact time with the 18F-FDG source or patient tracer.

DETERMINATION OF GUT BACTERIAL METABOLITES IN RADIATION EXPOSED MICE.

Gut microflora (GM) impacts human health in various ways, both beneficial and detrimental. Recently, it has attracted attention for its application in treatment, as protective agents, and as biomarkers in radiation exposure. In this study, we focused on organic acids that have not yet been reported to be related to radiation exposure; we measured the pH and organic acid content in the faeces of 0, 2, 4 and 8 Gy-irradiated mice. A common trend of fluctuation of some organic acids was observed in each group, suggesting a correlation between radiation exposure and organic acid fluctuation. Lactate fluctuation was similar between 0 and 2 Gy-, and 4 and 8 Gy-irradiated mice. Based on this finding, we suggest that lactate may also be an organic acid that is greatly affected by irradiation.

The Development of an Active Learning Program for the Medical Responders in a Nuclear Disaster.

OBJECTIVE: In Japan, with the revision of the Nuclear Emergency Response Guidelines in 2015, nuclear emergency medical assistance teams responsible for the medical treatment in the acute phase of nuclear disaster have been developed nationwide. The purpose of this research is to develop active learning materials for the education of medical staff, to confirm the educational effect of the materials, and to identify the gaps in nuclear disaster risk reduction in Japan. METHODS: We established a working group and created active learning materials. We trained members of the nuclear emergency medical assistance team using the developed active learning materials and then conducted a questionnaire survey for trainees who participated in the training. RESULTS: Regarding the developed teaching materials, out of 33 trainees, 33 (100%) answered "easy to understand" or "a little understandable" to the item dealing with how to use the radiation detectors and attaching/detaching personal protective equipment. Regarding the simulation about practicing hospital support and medical provision, 3 (8%) answered "a little confusing." CONCLUSION: The study demonstrated that the developed materials have an educational effect. Additionally, the results of the trainee questionnaire showed the necessity for improvement in the triage system and new protocols to help both the patients and responders.

Short-term follow-up of intestinal flora in radiation-exposed mice.

Some gastrointestinal bacteria, otherwise known as the 'intestinal flora', can cause severe gastrointestinal problems, including sepsis, which are strongly linked to lifestyle-related diseases, including cardiovascular diseases. Several investigations have focused on the long-term changes in the intestinal flora associated with radiation exposure; however, the short-term effects remain unknown. In this study, we tracked the short-term changes in the intestinal flora of mice exposed to different doses of X-ray irradiation (2 Gy and 4 Gy), focusing only on the lactic acid bacteria Bifidobacterium and Lactobacillus. A decrease in the Lactobacillus abundance was detected immediately after irradiation in individuals exposed to both 2 Gy and 4 Gy irradiation. However, mice exposed to 4 Gy of irradiation showed a remarkable increase in Bifidobacterium, indicating a potential role of these bacteria in regeneration of the intestinal epithelial tissue. Studies on changes in intestinal bacteria as a result of radiation exposure are limited. Therefore, continuation of this field of research is expected to provide important fundamental insight into the mechanisms by which radiation causes damage to the intestinal tissues, contributing to the development of sepsis.

Development of a method to extract protozoan DNA from black soil.

OBJECTIVES: Microorganisms in environmental samples are identified by sequential screening, isolation, and culture steps, followed by the verification of physiological characteristics and morphological classification. Isolation and purification of Amoebae from soil samples is extremely complex, laborious, and time-consuming and require considerable expertise for morphological evaluation. PCR testing of soil DNA seems to be an effective means for protozoa habitat screening. In this study, we added Acanthamoeba sp. (MK strain) to soil and developed a method of extracting protozoan DNA from the soil. METHODS: Soil allophane is a known DNA adsorbing substance that inhibits the PCR reaction. After comparing the soil properties and allophane contents of 7 soil samples, we attempted to combine multiple cell disruption and DNA purification methods to design an optimal soil DNA extraction method that can be used for downstream PCR analysis. RESULTS: We compared five different crushing/refining methods. Amplification of the gene was confirmed by Acanthamoeba specific PCR in protocol V where the concentration of Acanthamoeba in soil (1.0 × 102/g) was the detection limit of PCR. CONCLUSION: The soil DNA extraction method following protocol V allows DNA amplification of protozoa, including Amoeba, which is difficult to cultivate, thus simplifying the investigation of protozoa habitats and genetic analyses.

Comparative Study of Performance using Five Different Gamma-ray Spectrometers for Thyroid Monitoring under Nuclear Emergency Situations.

A performance test was carried out using five different gamma-ray spectrometers applicable to thyroid monitoring. The energy resolution and efficiency for 7.6-cm × 7.6-cm NaI(Tl), 5.1-cm × 5.1-cm CeBr3, 3.8-cm × 3.8-cm SrI2(Eu), and 2.5-cm × 2.5-cm SrI2(Eu) gamma-ray scintillation spectrometers and a CdTe gamma-ray semiconductor spectrometer were evaluated using the Oak Ridge Institute for Nuclear Studies thyroid-neck phantom with a mock I source for prompt thyroid monitoring after a nuclear emergency. The respective energy resolutions of the full-energy peak for ~0.360 MeV of 3.8-cm × 3.8-cm SrI2(Eu) and 2.5-cm × 2.5-cm SrI2(Eu) scintillation spectrometers were 4.2% and 4.3%, and these values were very close to the value obtained by the CdTe semiconductor spectrometer. The efficiencies of four of the gamma-ray spectrometers were compared based on the efficiency of the 7.6-cm × 7.6-cm NaI(Tl) scintillation spectrometer at 0 cm from the phantom surface, and these values were ~70% for 5.1-cm × 5.1-cm CeBr3, ~30% for 3.8-cm × 3.8-cm SrI2(Eu), 10% for 2.5-cm × 2.5-cm SrI2(Eu) and 2% for 1-cm × 0.1-cm CdTe. Furthermore, the detection limits at various dose rates for the four gamma-ray scintillation spectrometers were evaluated using the method based on International Organization for Standardization publication ISO 11929:2010.

Consideration of the usefulness of a size-specific dose estimate in pediatric CT examination.

Computed tomography (CT) has recently been utilized in various medical settings, and technological advances have resulted in its widespread use. However, medical radiation exposure associated with CT scans accounts for the largest share of examinations using radiation; thus, it is important to understand the organ dose and effective dose in detail. The CT dose index and dose-length product are used to evaluate the organ dose. However, evaluations using these indicators fail to consider the age and body type of patients. In this study, we evaluated the effective dose based on the CT examination data of 753 patients examined at our hospital using the size-specific dose estimate (SSDE) method, which can calculate the exposure dose with consideration of the physique of a patient. The results showed a large correlation between the SSDE conversion factor and physique, with a larger exposure dose in patients with a small physique when a single scan is considered. Especially for children, the SSDE conversion factor was found to be 2 or more. In addition, the patient exposed to the largest dose in this study was a 10-year-old, who received 40.4 mSv (five series/examination). In the future, for estimating exposure using the SSDE method and in cohort studies, the diagnostic reference level of SSDE should be determined and a low-exposure imaging protocol should be developed to predict the risk of CT exposure and to maintain the quality of diagnosis with better radiation protection of patients.

Characteristics of temporal resolution in 16- and 64-row computed tomography scanners.

This study aimed to analyze the temporal sensitivity profile (TSP) shapes and temporal resolutions of computed tomography (CT) and investigate the effect of a combination of a given rotation time and helical pitch on the TSP and image quality. The study was performed on 16- and 64-row CT scanners, and the TSP and temporal resolution were measured using the impulse method. A shorter gantry rotation time and larger helical pitch improved the temporal resolution of both CT scanners. Although the measured TSP shapes were dependent on the helical pitch, the maximum helical pitch did not improve the temporal resolution of either CT scanner. Different combinations of gantry rotation time and helical pitch yielded different TSP shapes such as the triangle, trapezoid, and rectangle, despite the use of equivalent scan speeds. We suggest that the different combinations of rotation time and helical pitch can greatly affect the TSP shapes.