We discriminated various concentrations’ contrast mediums by spectral photon-counting CT imaging. Contrast media increase the contrast of tissues in x-ray computed tomography (CT) imaging. Conventional x-ray CT uses contrast agent liquids including high x-ray absorption materials like iodine. Spectral photon-counting computed tomography (SPCCT) imaging has the capability of discriminate each contrast mediums with low concentration in one scan by their K-edge if its energy is located in the detectable energy range. The purpose of our research is to reveal the discriminability of contrast mediums by K-edge imaging under the various conditions of concentration included in a water included acrylic phantom with low x-ray exposure.
Recently, the photon counting X-ray imaging / CT systems have been researched and investigated as a next generation imaging system. CdTe has high attenuation coefficient at hard X-ray (100keV<) for medical imaging system, and photon counting signal processing has very high sensitivity in theoretic. We have demonstrated the photon counting X-ray imaging / CT system by CdTe detectors. The high-contrasted CT images of acryl phantom were taken by this system. In this case, very low power X-ray source (150kV, 1.8uA) was used. CT images could not be reconstructed at low exposure condition less than 9.0uAs in this protocol using traditional CdTe detector, but we could obtain good images by using photon counting CdTe detector even if the very low exposure of 1.8uAs. Photon-counting CT is very powerful technique for low exposure X-ray imaging / CT system.
X-ray imaging is popular in medical imaging, non-destructive testing and security. Main techniques of X-ray imaging with semiconductor detectors are charge accumulation and photon counting, and the photon counting is expected to identify materials at the same time with taking X-ray photograph by using energy information of X-ray photons. We proposed a direct charge handling method to build a photon counting system with energy information for X-ray imaging. This method operates the charge from the X-ray detector and converts it to encoded digital bit pattern directly without dead time of the front-end circuit. We simulated and built a proposed system to prove operating principals.
Irradiation of high resistivity p-like CdTe crystals pre-coated with an In dopant film from the CdTe side by nanosecond laser pulses with wavelength that is not absorbed by the semiconductor made it possible to directly affect the CdTe-In interface because radiation was strongly absorbed by a thin layer of the In film adjoining to the CdTe crystal. The doping mechanism was associated with the action of laser-induced stress wave which was generated under extreme conditions in the confined area at the CdTe-In interface under laser irradiation. The developed technique allowed avoiding evaporation of In dopant and resulted in the formation of the In-doped CdTe region and thus, creation of a built-in p-n junction. The temperature distribution inside the three layer CdTe-In-Water structure was calculated and correlations between the characteristics of the fabricated In/CdTe/Au diodes and laser processing conditions were obtained.
X-ray imaging is popular in medical imaging, non-destructive testing and security. The main techniques of x-ray imaging with semiconductor detector are charge accumulation and photon counting, and the photon counting is expected to identify materials at the same time with taking x-ray photograph by using energy information of x-ray photons. We proposed direct charge handling method to build photon counting system with energy information for x-ray imaging. This method operates the charge from x-ray detector and converts it to encoded digital bit pattern directly without dead time of front end circuit. We simulated and built proposed system to prove operating principals.
Proc. SPIE. 9968, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVIII
KEYWORDS: Detection and tracking algorithms, Sensors, Physics, Field programmable gate arrays, Imaging devices, Gamma radiation, Algorithm development, Hard x-rays, Data corrections, Current controlled current source
We have developed the current integration mode CdTe imaging device with 100fps movie mode. The pixel pitch is 100um, and detector size is about 50mm x 45 mm with 4-CdTe-ASIC units and 1mm thick-CdTe. The data correction algorithms were developed and installed in FPGA and MPU with real time collection. We can find clear image with high contrast as direct conversion, for example, pipe-edge thickness detection, penetration image and movie of mechanical watch and so on. We can observe detail connection in printed circuit board by using rotation movie mode. Also it has high sensitivity in high energy region, so we can apply to get real-time movie in operation. We will show the demonstration movie and detail of this detector.
The spatial resolution of scintillator type imaging detector is not so high because diffusion of luminescence in the
scintillator. As a countermeasure, the silicon substrate was processed to make a small grid by MEMS technique for
optical separation of scintillator. The silicon grid wall can completely obtain optical-separation for visible light as a
result of X-ray scintillation. Moreover, we can get large-size silicon wafers up to diameter of 30cm with high precision
semiconductor process. In this paper, the purpose is to fill a scintillator material such as CsI:Tl, inside of the grid
substrate. Because the aspect ratio of the grid is large (90μm x 90μm with 800μm depth), it is not easy to fill scintillator
inside the grid. Moreover, it is necessary to ensure uniformity, intention of light emission. In this study, the CsI:Tl was
filled inside of the grid by resistive heated evaporation method. We evaluated by X-ray luminescence and test chart.
The photon counting CdTe detector by using pulse rise height for high count rate detection was developed. The detector
can measure not only pulse rise height for energy estimation but also pulse rise time. The energy spectrum after
polarization in high bias voltage and before polarization in low bias voltage was so similar, but the pulse rise time was
difference. In this paper, we have compared polarization properties of M-p-n type CdTe diode and Schottky one. We will
estimate changing internal electric field by using this measurement.
Pulse laser was due to investigate characteristics of Schottky-diode type CdTe detector. The pulse laser was irritated to
cleaved surface of the CdTe detector to control incident position and time accurately. Even though one-photon energy of
the plse laser is different from that of γ-ray mainly detected by the CdTe detectors, amount of pulse energy of the laser
can be adjustable to the γ-ray energy by controlling incident power and pulse duration time. Incident position
dependence of electric signal through preamplifier was measured and the dependence was changed by charging bias
voltage applied to the CdTe detector. This dependence can be explained by distribution of depletion layer at the Schottky
To identify the factor impairing the material identification parameters, which is provided by the dual-energy X-ray
computed tomography method using a conventional X-ray tube and a CdTe detector, linear attenuation coefficient was
measured by the radioactivity of radio isotopes and compared with theoretical figure. In our study, the atomic number
and the electron density is calculated from the linear attenuation coefficient obtained in CT measurement by 64-channel
CdTe line detector. To estimate accuracy of CdTe line sensor, it is needed to obtain the linear attenuation coefficient
accurately. Using a single detector, the linear attenuation coefficient is verified for accuracy. The energy resolution of
CdTe detectors and the method of reconstruction are discussed.
Recently practical X-ray measurement systems are demanded energy distinction function. Photon-counting CdTe semiconductor detectors have a high energy resolution in a low count rate condition at room temperature. However, the energy resolution is decreased by pile-up phenomenon in a high count rate condition. In conventional signal processing, processing time estimated X-ray photon energy from the pulse waveform is about tens of microseconds. This time is depended on the pulse decay time. This paper purposes to maintain the high energy resolution by changing the signal-processing algorithm which derived the pulse rise height of the output waveform from the CdTe detector in a high count rate condition. As a result, the pulse rise time required to estimate the pulse rise height was short about 100ns at incident X-ray energy 60keV. As the result of energy spectrum by using this data, the FWHM of about 11keV (at 60keV) when the count rate of 500kcps. This result show the possibility that the photon counting sensor has application for the high count rate imaging without decrease of the high energy resolution.
The novel 3-D display system is required in the medical treatment field and non-destructive testing field. In these field, the X-ray CT system is used for obtaining 3-D information. However, there are no meaningful 3-D information in X-ray CT data, and there are also no practical 3-D display system. Therefore, in this paper, we propose an X-ray 3-D CT display system by combining a photon-counting X-ray CT system and a holographic image display system. The advantage of this system was demonstrated by comparing the holographic calculation time and recognizability of a reconstructed image.
A novel CdTe X-ray image sensor, which was driven by the FEA, was proposed in order to obtain high spatial resolution
X-ray images and have demonstrated the principle operation by using the CdTe image sensor with one pixel. We have
also fabricated a FEA matrix with 12x12 pixels to obtain X-ray images. For the further improvement of spatial resolution
in the CdTe image sensor, we have proposed a novel double-gated FEA with a focusing lens, which was fabricated by
using the etch-back method. The double-gated FEA showed a good focusing characteristic without significant decrease
of the emission current, when the height of the focus electrode was optimized. The CdTe image sensor driven by the
double-gated FEA is promising for an ultra-high-resolution X-ray image sensor.
The X-ray 3D CT data were detected by the CdTe semiconductor special detector which can obtain the energy
information of X-ray photon, and it is developed by our laboratory. In order to display this complete 3D
information with internal data of objects, the multi-color holographic reconstruction system was composed, and
the reconstruction of X-ray 3D CT data were examined in this paper. In this system, the electro-holography and
the computer generated holography was employed to display holographic images. In this case, we used the liquid
crystal display panel as the spatial light modulator for displaying a hologram, and we developed the simulator
to calculate a hologram of an X-ray 3D CT input data. Finally, it could represent effectively with three primary
colors, and understand easier the internal structure of objects.