Takuya Saze

In-vivo thyroid 125I monitoring method using imaging plate.

A new in vivo thyroid monitoring system was devised with radioluminography using an imaging plate. The counting features of the system were investigated by using a neck-thyroid phantom. A clear thyroid image was obtained at thin prethyroid tissue thicknesses and short distances between IP and neck surface. The characteristic 125I thyroid image made it possible to visually confirm that the thyroid definitely accumulated 125I. The counting efficiency in 100xcps Bq(-1) of the imaging plate system was determined by setting a region of interest on the thyroid image resulting in a maximum efficiency of 0.5%. The higher efficiency was obtained for thinner tissue thickness overlaying the thyroid, smaller thyroids, and shorter distances between the imaging plate and neck surface. The imaging plate thyroid monitoring system was sensitive to thyroid 125I. Its minimum detection limit of 23 Bq for a 10-min measurement was considerably lower than the annual thyroid burden limit of 300 kBq.

Application of ICP-DRC-MS to screening test of strontium and plutonium in environmental samples at Fukushima.

An application of sequential automated SPE separation equipment coupled to the quadrupole-based ICPMS instrumentation with a dynamic reaction cell such as a screening test system of (90)Sr and Pu isotopes in environmental samples was developed in this work. So far, during the course of a large number of reports as to various specific radioactivities in environmental samples surveyed at radioactive contaminated area around the Fukushima Daiichi Nuclear Power Plants (FDNPP), there is a much smaller number of reports on (90)Sr and Pu isotopes than that of (134)Cs and (137)Cs since the FDNPP accident, and then it would be expected to develop the simple analysis method of these isotopes instead of radiation measurements currently in use. In particular, a screening for (90)Sr in environmental samples has been accomplished using an isotopic ratio measurement mode in comparison with the characterization on the Solid Phase Elution (SPE) separation between strontium and zirconium isotopes around the mass-90 fraction. As a result, for a trial analysis of environmental samples of a muddy snow water and a soil which were collected at Fukushima, it was found that the present developed system makes it applicable for achieving up to the specific activity levels of several hundreds Bq/kg ((90)Sr) and about 1-2Bq/kg (Pu isotopes) as the screening test system.

Feasibility of in vivo thyroid 131I monitoring with an imaging plate

A new in vivo thyroid 131I monitoring method was devised by using an imaging plate (IP). A thyroid image obtained with a realistic neck-thyroid phantom showed a unique shape characteristic of the thyroid gland. A 131I thyroid imaging allows visual confirmation of thyroid accumulation of 131I. The detection limit of the IP system of 290 Bq was about 1/100 of the screening level of 30 kBq in cases of public emergencies. The IP system is applicable for thyroid 131I monitoring.

Automatic activity measurement and data processing system using image analyzer

Abstract An automated counting and data processing system for determining the radioactivity of 32 P was devised by using an image analyzer, an imaging plate, and a personal computer. This system can measure 18 samples containing 32 P concurrently and print out the results as a report.

Feasibility of in vivo measurement of 239Pu distribution in lungs using an imaging plate

An in vivo measurement system using an imaging plate (IP) system was developed, which displayed images reflecting (239)Pu distribution in the lung of a phantom. The detection limits of the IP system for 1-12h exposures were between 1670 and 245 Bq at a 1.6 cm chest wall thickness. The detection limit of the IP system for a 2.5h exposure was equal to that of a germanium detector for a 0.5h measurement. The IP system could be used as a new device for in vivo measurement of (239)Pu in the lung.

Development of 241Am lung monitoring system using an imaging plate

A new 241Am lung monitoring system without shielding was devised by using an imaging plate system. The Lawrence Livermore National Laboratorys realistic torso phantom containing a 241Am lung was covered by imaging plates sealed in lightproof bags. The imaging plate system displayed 241Am lung images characteristic of the lung shape of the torso phantom. The imaging plate systems lower detection limits of 14 Bq for 60 min exposure and 6 Bq for 300 min were the same levels as those of the phoswich detectors and the germanium detectors placed in shielded rooms. The imaging plate system for 60 min exposure detected about 2% of the annual limit of 740 Bq for 241Am inhalation. A lung monitoring system using imaging plates is applicable for 241Am lung monitoring. Health Phys. 93(1):28–35; 2007

DEVELOPMENT OF ELEMENTAL AND ISOTOPIC ANALYSIS OF URANIUM AND THORIUM IN MATERIAL USING AN AUTOMATIC SPE INJECTION EQUIPMENT COUPLED TO ICP-DRC-MS

We have investigated to elucidate the relationship between specific activities of radionuclides and elemental concentrations of trace elements in environment and materials. In 2010 the funding for bigger equipment cost of ICPMS (Inductively Coupled Plasma Mass Spectrometry) and automated SPE (Solid Phase Elution) was allowed to insert it in the national revised budget for The University of Tokushima. In this paper, we have briefly introduced a new integrated instrumental system based on ICPMS and SPE for radiation measurement and multi trace elemental analysis.

99mTc thyroid imaging system using multiple imaging plates

A system for taking static thyroid (99m)Tc images was devised by using multiple imaging plates (IPs) and a low-energy high resolution collimator. System spatial resolution of the IP systems and the gamma camera was determined by referring to standards set by the National Electrical Manufacturers Association. Sensitivity was represented by using lower detection limits (LDLs). The sensitivity and resolution of IP systems using 16 IP probes connecting two collimators and 9 IPs were determined by using a 20 ml thyroid phantom, and compared with the sensitivity of gamma cameras. The sensitivity of the IP systems increased in proportion to the number of IPs. The sensitivity and resolution of a probe using 6 IPs and a high resolution collimator were equivalent to or superior to the gamma camera for taking static thyroid (99m)Tc images. IP systems can be applied clinically as mobile static nuclear imaging devices. The performance of IP systems should be thoroughly investigated for combinations of various collimators and the number of IPs in order to verify their efficacy for imaging all organs.

Properties of signal intensities observed with individual probes of GeneChip Rat Gene 1.0 ST Array, an affymetric microarray system

For proper evaluation of the results of microarray experiments, it is important to understand how the signal intensities of individual probes are determined. Our previous studies revealed that signal intensities of individual probes in the Agilent array system (code G4131F) are largely dependent upon the location of the probes in the mRNA. In the present study, we examined the properties of signal intensities of individual probes in an Affymetrix array system (GeneChip Rat Gene 1.0 ST Array), in which a random primer fused to the T7 promoter sequence is employed. Distinct from the Agilent array system, individual probes used in this Affymetrix array system did not show the probe-location effects, but gave relatively diverse signal intensities. However, the diversities of the signal intensities of these individual probes were not due to experimental error.

Radiation effects on communication performance of radio frequency identification tags.

Radioactive materials (sources) are managed by bookkeeping and stocktaking. The radiation protection section staffs should check the sources manually. Annual effective dose concerning stocktaking of them are estimated at some mSv concerning fingers. A radio frequency identification (RFID) tags absorbed dose is estimated at some dozen Gy. RFID for stocktaking automatically was devised. Radiation effects on the communication performance of RFID tags were investigated by using response times and read ranges as indices. The RFID system was composed of a computer, a detector, and transponders (tag) consisting of an integrated circuit chip and an antenna. The tag is joined to the source for identification. The tags were irradiated at doses between 5 and 5,000 Gy by an x-ray irradiator. The response times and the read ranges were tracked from 40 to 23,200 min after irradiation. Relative read ranges fluctuated between 0.9 and 1.1 in the dose region less than 2,000 Gy, but fluctuated greatly in the dose region beyond 2,000 Gy. Malfunctioning tags appeared from 3,000 Gy, and all tags malfunctioned in the dose region over 4,500 Gy. The threshold dose leading to malfunction was determined to be 2,100 Gy. Time variation of relative read ranges was classified into four patterns. The pattern shifted from pattern 1 to 4 when the dose was increased. The relative read ranges lengthened in pattern 1. The relative read rages were approximately 1.0 in pattern 2. The read ranges tentatively shortened, then recovered in pattern 3. The tags malfunctioned in pattern 4. Once the tags malfunctioned, they never recovered their performance. Radiation enhances or deteriorates communication performance depending on dosage. Tags can spontaneously recover from radiation deterioration. The time variation of the read ranges can be illustrated by enhancement, deterioration, and recovery. The mechanism of four patterns is explained based on the variation of the frequency harmonization strength and activation voltage by irradiation. The annual effective dose of radiation protection section staffs can be reduced considerably.