Speaker
Mr
Peng Cong
(Institute of Nuclear and New Energy Technology, Tsinghua University; Beijing Key Laboratory on Nuclear Detection and Measurement Technology, China)
Description
Methods like single-projection detecting and CT detecting are widely
used in radiation scanning systems, however, these methods have
shortages such as an inability to differentiate materials and low
efficiency so that methods with high accuracy and efficiency are
required.
In this paper, we introduce a dual-projection radiation detection
technique. Two groups of radioactive sources and detectors are fixed
to obtain gray-scale images of target objects from two orientations.
Algorithms are developed to combine these images and calculate the
shape, position, attenuation coefficient and density of target objects
rapidly and accurately. Ideally, target objects are assumed as convex
polygons of single material. The gray-scale curves follow the ray
attenuation theorem which contains physical property information such
as attenuation coefficient and density. Inflections on the curve show
when vertexes on target objects are scanned. To recover the target
object geometry from gray-scale images, algorithms are developed with
functions as follows:
1. Locating the position of each inflection on the curves and
calculating their coordinates in real space coordinate where the
vertexes are.
2. Combining these calculated vertexes to form polygons and remove
those that do not meet the mentioned assumptions.
3. The selected polygons are re-projected by emulation. The
calculated polygon whose gray-scale curves are closest to the ones of
target object is chosen as the result of recovering. And its position,
shape and density can also be calculated.
Matlab simulations were performed, verifying the feasibility of the
algorithms. Given $10$ mm detectors and an arbitrary pentagon target
object, the result shows that the relative error of calculated
absorption coefficient is $0.33\%$.
Realistic experiments with ideal target were performed. Standard
aluminium blocks with sections of quadrilateral and pentagon are used
as the target. The detectors are $7$ mm in size and the radioactive
source is $^{60}$Co. The relative error of calculated density
is within $3$–$5$%. The difference between two experiment results of
absorption coefficient is $4\times10^{-3}$ which shows the high
reproducibility of this system. Further experiments using non-ideal
objects were made. A bucket of water was put in a container as the
target. By moving the container continuously, a series of gray-scale
curves, representing different sections of all things in it,
are obtained and processed to recover the shape and position. The
results show that the relative error of calculated density is
$10.4$% after eliminating the impact of background noise.
Details of the method and its application will be presented.
| Country/Organization invited to participate | China |
|---|
Primary author
Ms
Xi Zhao
(Institute of Nuclear and New Energy Technology, Tsinghua University; Shanghai Nuclear Engineering Research and Design Institute, China)
Co-authors
Mr
Litao Li
(Institute of Nuclear and New Energy Technology, Tsinghua University; Beijing Key Laboratory on Nuclear Detection and Measurement Technology, China)
Mr
Peng Cong
(Institute of Nuclear and New Energy Technology, Tsinghua University; Beijing Key Laboratory on Nuclear Detection and Measurement Technology, China)
Mr
Xincheng Xiang
(Institute of Nuclear and New Energy Technology, Tsinghua University; Beijing Key Laboratory on Nuclear Detection and Measurement Technology, China)
Mr
Yanmin Zhang
(Institute of Nuclear and New Energy Technology, Tsinghua University; Beijing Key Laboratory on Nuclear Detection and Measurement Technology, China)
