Speaker
Prof.
KEIZO ISHII
(TOHOKU UNIVERSITY, SCHOOL OF ENGINEERING)
Description
In Particle Induced X-ray Emission (PIXE), the production cross sections of
characteristic X-rays are very large in comparison to those of continuous X-rays,
which when integrated over the detector resolution are typically 3 orders of
magnitude smaller. This feature is quite different from the case of electron
bombardment, where the electron bremsstrahlung contributes predominantly to the X-
ray spectrum. Due to this inherent advantage, X-rays from a pure metal target
bombarded with micro-beams can be considered to constitute a monochromatic X-ray
source.
We use this feature in an X-ray CT, which then provides the 3 dimensional structure
of a small object with a resolving power of micron size. On the basis of this idea,
we develop 3D imaging consisting of a micro-beam system and an X-ray CCD camera.
The performance of the X-ray CCD camera( Hamamatsu photonics C8800X) is as
follows : element size is 8mm 8mm, and the total number of image elements 1000 1000
provides an image size 8mm 8mm. A biological sample is placed in a tube with inside
diameter 1000mm and wall thickness 25mm. This tube is rotated by a stepping motor
and 2D transmission images of the sample are taken with characteristic K-X-rays
produced from a metal target bombarded by 3MeV proton micro-beams. 3D images are
reconstructed from these 2D projection images by using an iteration method. We
applied our system to investigate an in-vivo sample, in this case being a very
small ant. The ant was anaesthetized with chloroform and exposed to characteristic
X-rays of Ti. The 3D image of the ant was obtained with a spatial resolution of
4mm. In the usual X-ray CT, X-rays of ~60keV are used and the images reflecting the
density of object are obtained. In our case, due to absorption edge and the strong
dependence on atomic number of photo ionization cross sections, we obtain images
emphasizing the contribution from heavier element. The distribution of K in the
gnathic glandula could be clearly imaged.
It is expected that our 3D imaging system could provide cross sectional images of
in-vivo samples with high spatial resolution and may thus be applied to a wide
range of researches in biology and medicine.
Author
Prof.
KEIZO ISHII
(TOHOKU UNIVERSITY, SCHOOL OF ENGINEERING)
Co-authors
Ms
Azusa Ishizaki
(TOHOKU UNIVERSITY, SCHOOL OF ENGINEERING)
Dr
Genki Momose
(TOHOKU UNIVERSITY, SCHOOL OF ENGINEERING)
Prof.
Hiromichi Yamazaki
(TOHOKU UNIVERSITY, SCHOOL OF ENGINEERING)
Dr
Shigeo Matsuyama
(TOHOKU UNIVERSITY, SCHOOL OF ENGINEERING)
Dr
Takashi Yamaguchi
(TOHOKU UNIVERSITY, SCHOOL OF ENGINEERING)
Mr
Yoshito Watanabe
(TOHOKU UNIVERSITY, SCHOOL OF ENGINEERING)
Dr
Youhei Kikuchi
(TOHOKU UNIVERSITY, SCHOOL OF ENGINEERING)
