| Budget Amount *help |
¥4,600,000 (Direct Cost: ¥4,600,000)
Fiscal Year 1995: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1994: ¥4,000,000 (Direct Cost: ¥4,000,000)
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| Research Abstract |
The paramagnetic radicals (SO_3, SO_4) are produced in lanthanide (Ln) ion-doped glaserite crystal (K_3Na (SO_4) _2) after X-ray irradiation. The SO_3^- radical was isotropic and thermally stable. The ESR signal intensity of SO_3^- radical was remarkably high in Gd ion-or Y ion-doped K_3Na (SO_4) _2. In order to investigate production mechanism of SO_3^- radical, the existence of Ln ion in host crystal was measured by means of thermoluminescence (TL) spectroscopy. K_3Na (SO_4) _2 doped with Pr, Nd, Gd, Y,or Tm ion revealed the TL spectrum derived from the transition of trivalent Ln ion. Especially, TL of K_3Na (SO_4) _2 doped with Gd ion or Y ion was strongly bright. However, K_3Na (SO_4) _2 doped with stable trivalent La ion did not reveal the TL spectrum. K_3Na (SO_4) _2 doped with Eu ion or Sm ion revealed the TL spectrum due to the transition of divalent Eu ion or the transitions of divalent and trivalent Sm ion, respectively. The results obtained suggest that the production of SO_
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3^- radical was remarkably promoted by doping stable trivalent Ln ion of which size is similar to one of Na ion in host crystal.
We attempted the application of the Gd ion-doped K_3Na (SO_4) _2 to the ESR imaging method which can monitor both absorbed dose and irradiation direction. Zupancic-typed coils were used to produce the magnetic field gradient with a direction for ESR imaging. The parallel wires of Zupancic-typed coils were connected to each other and to the current sources, forming four independent current loops to change the direction of magnetic field. The ESR spectrum were measured using an X-band ESR spectrometer with a 100kHz magnetic field modulator and a phase-sensitive detector. The current values of the four loops were controlled by using four regulated DC power supplies controlled 12 bit D/A converters. A two-dimensional image was reconstructed using a filtered back projection (FBP) method from the projection data of 180 directions (1-degree steps), which were obtained by using a field gradient of 1.05mT mm^<-1>. The obtained results suggested that the Gd ion-doped K_3Na (SO_4) _2 can be utilized as the ESR-CT image and the ESR dosimeter in the range from 20 mu Gy to 100Gy. Less
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