Summary of temporal changes in air dose rates and radionuclide deposition densities in the 80 km zone over five years after the Fukushima Nuclear Power Plant accident.

We summarized temporal changes in air dose rates and radionuclide deposition densities over five years in the 80 km zone based on large-scale environmental monitoring data obtained continuously after the Fukushima Nuclear Power Plant (NPP) accident, including those already reported in the present and previous special issues. After the accident, multiple radionuclides deposited on the ground were detected over a wide area; radiocesium was found to be predominantly important from the viewpoint of long-term exposure. The relatively short physical half-life of Cs (2.

Changes in ambient dose equivalent rates around roads at Kawamata town after the Fukushima accident.

Changes in ambient dose equivalent rates noted through vehicle-borne surveys have elucidated ecological half-lives of radioactive caesium in the environment. To confirm that the ecological half-lives are appropriate for predicting ambient dose equivalent rates within living areas, it is important to ascertain ambient dose equivalent rates on/around roads. In this study, radiation monitoring on/around roads at Kawamata town, located about 37 km northwest of the Fukushima Daiichi Nuclear Power Plant, was performed using monitoring vehicles and survey meters.

Development of prediction models for radioactive caesium distribution within the 80-km radius of the Fukushima Daiichi nuclear power plant.

Preliminary prediction models have been studied for the radioactive caesium distribution within the 80-km radius of the Fukushima Daiichi nuclear power plant. The models were represented by exponential functions using ecological half-life of radioactive caesium in the environment. The ecological half-lives were derived from the changes in ambient dose equivalent rates through vehicle-borne surveys.

Assessment of olfactory nerve by SPECT-MRI image with nasal thallium-201 administration in patients with olfactory impairments in comparison to healthy volunteers.

Purpose: The aim of this study was to assess whether migration of thallium-201 ((201)Tl) to the olfactory bulb were reduced in patients with olfactory impairments in comparison to healthy volunteers after nasal administration of (201)Tl.

Procedures: 10 healthy volunteers and 21 patients enrolled in the study (19 males and 12 females; 26-71 years old). The causes of olfactory dysfunction in the patients were head trauma (n = 7), upper respiratory tract infection (n = 7), and chronic rhinosinusitis (n = 7).

Evaluation of absorbed doses in voxel-based and simplified models for small animals.

Internal dosimetry in non-human biota is desirable from the viewpoint of radiation protection of the environment. The International Commission on Radiological Protection (ICRP) proposed Reference Animals and Plants using simplified models, such as ellipsoids and spheres and calculated absorbed fractions (AFs) for whole bodies. In this study, photon and electron AFs in whole bodies of voxel-based rat and frog models have been calculated and compared with AFs in the reference models.

Computer simulations for internal dosimetry using voxel models.

In the Japan Atomic Energy Agency, several studies have been conducted on the use of voxel models for internal dosimetry. Absorbed fractions (AFs) and S values have been evaluated for preclinical assessments of radiopharmaceuticals using human voxel models and a mouse voxel model. Computational calibration of in vivo measurement system has been also made using Japanese and Caucasian voxel models.

Evaluation of counting efficiencies of a whole-body counter using Monte Carlo simulation with voxel phantoms.

In the 2007 recommendations of the International Commission on Radiological Protection, it is mentioned that the reference voxel phantoms are used for calculation of effective dose. From the standpoint of internal dosimetry services, calibration methods of whole-body counters using the voxel phantoms are of considerable practical interest. In the present study, counting efficiencies of a whole-body counter at the Japan Atomic Energy Agency (JAEA) were evaluated using Monte Carlo simulations with two voxel phantoms, 'MAX06', which has organ masses corresponding to those of the reference male, and 'Otoko', which is a representation for average Japanese male.

Evaluation of self-dose S values for positron emitters in voxel phantoms.

In recent years, concern has been raised about patient-specific doses due to the increased use of PET imaging. It is of scientific and practical interest for the accurate quantification of the doses to patients administered a radiopharmaceutical for PET imaging. In the present study, Monte Carlo simulations have been carried out to evaluate S values--the mean absorbed dose to the target region per unit cumulated activity in the source region--for positron emitters in the brain, heart and the urinary bladder content.

Development of lung and soft tissue substitutes for photons.

The use of solid tissue substitutes is a well-accepted and common practice in dosimetric studies and in the production of counting standards for radiological protection. However, only a few solid tissue substitutes simulating a particular body tissue with respect to a set of physical characteristics are commercially available. Hence, we have developed polyurethane-based tissue substitutes simulating soft tissue, muscle, muscle-adipose mixture tissue (90% muscle + 10% adipose), brain, cartilage, larynx, thyroid, trachea, liver, kidney, skin and lungs.