The plasma display panel (PDP) is popular in the large area flat panel display market due to its relatively simple cell
structure, low cost materials, and uncomplicated manufacturing process. The cell structure of PDP, which consists of
electrodes and gas mixture, could be utilized in the manufacture of radiation detectors. In this study, we developed a
plasma display panel based x-ray detector (PXD) based on Monte-Carlo simulation. This prototype detector panel has
row and column strips, and it can thus be utilized as an imaging detector. To achieve the 2D x-ray image from the
developed panel, a PXD dedicated driving and data acquisition circuit has been developed. Now we integrate the
individual modules into a system. We hope to further study signal processing to achieve the first x-ray image of PXD.
We developed a high precision position decoding method for a positron emission tomography (PET) detector that consists of a thick slab scintillator coupled with a multichannel photomultiplier tube (PMT). The DETECT2000 simulation package was used to validate light response characteristics for a 48.8 mm×48.8 mm×10 mm slab of lutetium oxyorthosilicate coupled to a 64 channel PMT. The data are then combined to produce light collection histograms. We employed a Gaussian mixture model (GMM) to parameterize the composite light response with multiple Gaussian mixtures. In the training step, light photons acquired by N PMT channels was used as an N-dimensional feature vector and were fed into a GMM training model to generate optimal parameters for M mixtures. In the positioning step, we decoded the spatial locations of incident photons by evaluating a sample feature vector with respect to the trained mixture parameters. The average spatial resolutions after positioning with four mixtures were 1.1 mm full width at half maximum (FWHM) at the corner and 1.0 mm FWHM at the center section. This indicates that the proposed algorithm achieved high performance in both spatial resolution and positioning bias, especially at the corner section of the detector.
Statistically based iterative algorithms such as maximum likelihood-expectation maximization (ML-EM) are used for image reconstruction in single photon emission computed tomography (SPECT). Unmatched projector/backprojector pairs are sometimes used to accelerate the iteration process in the reconstruction algorithm. In this work, we propose and explore the use of an unmatched projector/backprojector pair for demultiplexing in multipinhole SPECT. Several simulations are conducted to evaluate the performance of the proposed method with uniform, hot-rod, and cold-rod phantoms. The proposed method incorporates an unmatched backprojector to utilize selective multiplexed projection data in reconstruction algorithms, while the projector is modeled as accurately as possible to represent realistic imaging geometry and the physical effects of multipinhole SPECT. The root mean square (rms) error and backprojection speed are evaluated to determine an unmatched backprojector. Our results demonstrate that the proposed method provides high-quality multipinhole SPECT images without multiplexing-related artifacts when a well-chosen unmatched backprojector is used.
In this study 2-dimensional plasma simulation code was used to find a new approach of x-ray detection method with
PDP-like geometry and condition. A conventional PDP geometry consisted of three electrodes was selected and Ne-Xe
composition gas was filled the cell-gap. Depending on incident X-ray energy, the number of charges generated within
the cell-gap could be different. For the charge amplification and collection of charges two consecutive ac pulses were
applied to scan and address electrodes. The increased charges were collected on the positive-bias address electrode at the
rear panel. Two parameters, such as amplitude of collected current and formation delay of collected current, were
calculated and compared. The formation delay showed more accurate relationship than the collected current amplitude.
Conventional gamma cameras which uses photomultiplier tubes(PMT) is very heavy, bulky, and
expensive. In addition, its spatial resolution is low because of geometrical limitation of PMTs. This
low resolution and large size is not efficient for the small animal imaging system which is useful in
preclinical imaging application. We have developed a small size but high spatial resolution gamma
ray detector, based on charge-coupled device(CCD) which is useful to develop a prototype model of
small animal gamma camera. Recently the sensitivity of CCD was improved and the peltier cooling
system helped to minimize the dark currents of CCD significantly. The enhanced sensitivity and
high intrinsic resolution of CCD enabled researchers to develop the small size gamma camera with
low cost. In this study we used peltier cooled CCD sensor which has about 70% of quantum
efficiency at 650nm wave length. CsI(Tl) scintillator was also used to convert the gamma ray to
visible lights. These light photons from the scintillator have been collected to the CCD surface by
Nikorr macro lens to enhance the collection efficiency. The experimental results showed that the
proposed CCD-based detection system is feasible for gamma ray detection.
PIN diodes for digital X-ray detection as a single photon counting sensors were fabricated with a guard ring structure
with p+ doping for reducing the leakage current. The efficiency of the guard ring was verified by significantly reduced
leakage current compared to the Si-PIN diodes without guard ring structure and the gap distance between the active area
and the guard ring was optimized as the leakage currents showed strong dependency on it. In this paper, secondary ion
mass spectroscopy (SIMS) profile was measured and characterized to investigate potential process improvement. Since a
large transient enhanced diffusion (TED) as the broadening of 200 nm at the tail is observed in the boron SIMS profile, it
is suggested to reduce the annealing process time of RTA or to use spike annealing process. Also, in order to investigate
the effect of reduced TED or other possible process to achieve shorter junction depth for improving device performance,
it is in progress to fully optimize the process simulation incorporating the transient enhanced diffusion model of boron in